close

Вход

Забыли?

вход по аккаунту

?

JP2008252932

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2008252932
An object of the present invention is to detect resonance frequencies separately from feedback
frequencies. A method for detecting a resonance frequency comprises: loudening a reference
frequency signal lasting for a predetermined time from a speaker arranged in a resonance space,
receiving the sound by a microphone arranged in the resonance space, and outputting an output
signal of the microphone Attenuation characteristic measurement step of measuring an
attenuation characteristic is provided, and a resonance frequency of the resonance space is
detected based on the attenuation characteristic. The reference frequency signal is a sine wave
signal of a specific frequency or a signal having a component within a predetermined frequency
width centered on the specific frequency. [Selected figure] Fig. 18
Resonance frequency detection method and resonance frequency detection device
[0001]
The invention according to this application relates to a resonance frequency detection method
and a resonance frequency detection apparatus for detecting a resonance frequency of a
resonance space.
[0002]
It may be necessary to detect the resonance frequency of the resonance space.
For example, when an acoustic equipment such as a speaker is installed in a hall or a gymnasium
08-05-2019
1
etc. and loud sound is emitted from the speaker, music or the like from the speaker is generated
because of the resonance frequency of this space (the loud space where the acoustic equipment
is arranged). Sometimes speaking is difficult to hear. That is, when the component of the
resonance frequency is included in the loud sound from the speaker, resonance occurs at the
frequency of this component in the loud sound space. The resonance sounds like "Won Won ..."
or "Fun Fan ...". This resonant sound is not originally intended to be radiated from the speaker,
but makes it difficult to hear music and speech from the speaker.
[0003]
In order to prevent this, it is preferable to detect a resonance frequency in the loud space, and to
provide a dip filter or the like that attenuates the component of the resonance frequency at a
stage prior to the speaker in the acoustic equipment. Then, resonance is less likely to occur in
this loud space, and music and speech from the speaker become easy to hear. In order to
determine the frequency characteristics of this dip filter, it is first necessary to detect the
resonance frequency of this sounding space.
[0004]
Heretofore, an operator or a measurer of an acoustic equipment has decided to distinguish a
resonance frequency by listening to a speaker's loud sound or resonance sound by relying on his
/ her hearing.
[0005]
However, it takes some skill and experience to determine whether or not the resonance
frequency is based on such distinction.
In addition, detection based on such skill and experience can not always detect the accurate
resonance frequency.
[0006]
Moreover, it is difficult for the auditor to distinguish between the resonant frequency and the
08-05-2019
2
feedback frequency even for a certain degree of expert. The resonance frequency is a frequency
determined by the characteristics of the resonance space, and the feedback frequency is a
frequency determined by the configuration of the feedback loop including the electroacoustic
system, but both may sound similar in hearing. And these things also became an obstacle for
automatic measurement and automatic adjustment of the sound equipment installed in the loud
sound space etc.
[0007]
An object of the present invention is to provide a resonance frequency detection method and
device that can accurately detect a resonance frequency without requiring experience or skill. In
particular, it is an object of the present invention to provide a method and an apparatus for
detecting a resonant frequency which can detect a resonant frequency separately from a
feedback frequency.
[0008]
In order to solve the above problems, according to the resonance frequency detection method of
the present invention, a reference frequency signal lasting for a predetermined time is amplified
from a speaker disposed in a resonance space and received by a microphone disposed in the
resonance space. A resonance frequency detection method comprising: an attenuation
characteristic measurement step of measuring an attenuation characteristic of an output signal of
the microphone, and detecting a resonance frequency of the resonance space based on the
attenuation characteristic, wherein the reference frequency signal is specified It is a sine wave
signal of a frequency or a signal having a component within a predetermined frequency width
around a specific frequency.
[0009]
Further, in order to solve the above problems, a resonance frequency detection device according
to the present invention includes a sound source means and a measurement means, and the
sound source means can generate and output a measurement signal, and the measurement signal
Is a reference frequency signal lasting for a predetermined time, the reference frequency signal is
a sine wave signal of a specific frequency or a signal having a component within a predetermined
frequency width centered on a specific frequency, and the measurement means is a microphone
An output signal can be input, and the measurement means measures an attenuation
characteristic of the output signal of the microphone, and detects a resonance frequency based
on the attenuation characteristic.
08-05-2019
3
[0010]
Further, in order to solve the above problems, yet another resonance frequency detection method
according to the present invention includes a reference frequency signal lasting for a
predetermined time from a speaker disposed in the resonance space, and a microphone disposed
in the resonance space. Attenuation characteristic measuring step of amplifying an output signal
and receiving the sound by the microphone and measuring an attenuation characteristic of the
output signal of the microphone, and detecting a resonance frequency of the resonance space
based on the attenuation characteristic In the frequency detection method, the reference
frequency signal is a sine wave signal of a specific frequency or a signal having a component
within a predetermined frequency width centered on the specific frequency.
[0011]
Further, in order to solve the above-mentioned problems, still another resonance frequency
detection device according to the present invention comprises a sound source means, a signal
output means, and a measurement means, the sound source means generates a measurement
signal, The measurement signal is a reference frequency signal that lasts for a predetermined
time, and the reference frequency signal is a sine wave signal of a specific frequency or a signal
having a component within a predetermined frequency width around a specific frequency, and
the signal output means Can input the measurement signal from the sound source means and the
output signal of the microphone, and the signal output means can output the measurement signal
and the output signal of the microphone by the speaker. The measuring means can input the
output signal of the microphone, and the measuring means measures the attenuation
characteristic of the output signal of the microphone and detects the resonance frequency based
on the attenuation characteristic. To.
[0012]
In the above method and apparatus, when the attenuation rate obtained from the attenuation
characteristic is slower than a predetermined attenuation rate, a specific frequency of the
reference frequency signal may be determined as the resonance frequency.
[0013]
Further, in order to solve the above-mentioned problems, still another resonance frequency
detection method according to the present invention is characterized in that a reference
frequency signal intermittently repeated plural times from a speaker arranged in the resonance
space, and arranged in the resonance space And an attenuation characteristic measurement step
08-05-2019
4
of receiving the sound by the microphone and measuring the attenuation characteristic of the
output signal of the microphone. A resonance frequency detection method for detecting a
resonance frequency of the resonance space based on characteristics, wherein the delay time
changes in synchronization with intermittent repetition of the reference frequency signal, and the
reference frequency signal is identified. It is a sine wave signal of a frequency or a signal having
a component within a predetermined frequency width around a specific frequency.
The reference frequency signal may be delayed together with the output signal of the
microphone and may be loudened from the speaker, or may be loudened from the speaker
without being delayed.
[0014]
Further, in order to solve the above-mentioned problems, still another resonance frequency
detection device according to the present invention comprises a sound source means, a signal
output means, and a measurement means, the sound source means generates a measurement
signal, The measurement signal is a reference frequency signal that is intermittently repeated
plural times, and the reference frequency signal is a sine wave signal of a specific frequency or a
signal having a component within a predetermined frequency width centered on the specific
frequency, The signal output means can input the measurement signal from the sound source
means and the output signal of the microphone, and the signal output means outputs the
measurement signal and the output signal of the microphone with a delay time of 0 or more. The
signal output means can change the delay time in synchronization with the intermittent
repetition of the reference frequency signal, and the measurement means can change the delay
time, so that the delayed delayed signal can be amplified by the speaker. And can input the
output signal of Ikurohon, said measuring means measures an attenuation characteristic of the
output signal of the microphone, based on the attenuation characteristics, to detect the resonant
frequency.
The reference frequency signal may be delayed together with the output signal of the
microphone and may be loudened from the speaker, or may be loudened from the speaker
without being delayed.
[0015]
In the above method / apparatus, it is judged whether or not the attenuation characteristic
changes due to the change of the delay time, and when it is judged that the attenuation
08-05-2019
5
characteristic changes due to the change of the delay time, The specific frequency of the
reference frequency signal may not be determined as the resonance frequency.
[0016]
Further, in order to solve the above-mentioned problems, still another resonance frequency
detection method according to the present invention is characterized in that a reference
frequency signal intermittently repeated plural times from a speaker arranged in the resonance
space, and arranged in the resonance space A first output state for amplifying the output signal
of the microphone, or a reference frequency signal intermittently repeated several times, and a
phase inversion signal obtained by inverting the phase of the output signal of the microphone
disposed in the resonance space Selecting a second amplification state for amplifying the sound,
receiving the sound by the microphone, and measuring an attenuation characteristic of an output
signal of the microphone, and based on the attenuation characteristic, determining the resonance
frequency of the resonance space A resonance frequency detection method for detecting, in
synchronization with an intermittent repetition of the reference frequency signal, a sound
amplification state is changed from the first sound amplification state to the second sound
amplification state To, or is changed from the second loudspeaker state to said first loudspeaker
state, the reference frequency signal is a signal having components at a predetermined frequency
within the width around the sine wave signal or a specific frequency of a specific frequency.
The reference frequency signal may be phase-inverted together with the output signal of the
microphone and may be amplified from the speaker, or may be amplified from the speaker
without phase inversion.
[0017]
Further, in order to solve the above-mentioned problems, still another resonance frequency
detection device according to the present invention comprises a sound source means, a signal
output means, and a measurement means, the sound source means generates a measurement
signal, The measurement signal is a reference frequency signal that is intermittently repeated
plural times, and the reference frequency signal is a sine wave signal of a specific frequency or a
signal having a component within a predetermined frequency width centered on the specific
frequency, The signal output means can input the measurement signal from the sound source
means and the output signal of the microphone, and the signal output means uses the speaker
for the state and the measurement signal and the output signal of the microphone. A first output
08-05-2019
6
state to be output for amplification, or a second output state for amplifying by the speaker the
signal for measurement and a phase inversion signal obtained by inverting the phase of the
output signal of the microphone The state of the signal output means is selectively configurable
from the first output state to the second output state or in synchronization with the intermittent
repetition of the reference frequency signal. The second output state is changed to the first
output state, and the measurement means can input the output signal of the microphone, the
measurement means measures the attenuation characteristic of the output signal of the
microphone, and the attenuation characteristic To detect the resonant frequency.
The reference frequency signal may be phase-inverted together with the output signal of the
microphone and may be amplified from the speaker, or may be amplified from the speaker
without phase inversion.
[0018]
In the above method, it is judged whether or not the attenuation characteristic changes due to
the change of the sound amplification state, and when it is judged that the attenuation
characteristic changes due to the change of the sound amplification state, the reference
frequency The specific frequency of the signal may not be determined as the resonance
frequency, and in the above apparatus, the measuring means may change whether the
attenuation characteristic changes due to a change in the state of the signal output means. If it is
determined that the attenuation characteristic changes due to the change of the state of the
signal output means, the specific frequency of the reference frequency signal may not be
determined as the resonance frequency.
[0019]
Further, in the method and apparatus for detecting the resonance frequency based on the above
attenuation characteristics, the measurement of the attenuation characteristics may be repeated
multiple times while changing the specific frequency of the reference frequency signal.
[0020]
According to the present invention, the resonance frequency can be accurately detected without
the need for experience or skill, and the frequency to be set as the dip center frequency in the dip
filter can be appropriately selected.
[0021]
Embodiments of the present invention will be described with reference to the drawings.
08-05-2019
7
[0022]
FIG. 1 is a schematic block diagram of an acoustic system installed in a loud-speaking space (e.g.,
a resonance space where resonance occurs such as a concert hall or a gymnasium) 40.
The acoustic system includes a sound source device 2, a dip filter 4, an amplifier 12, and a
speaker 13.
The sound source device 2 may be, for example, a musical instrument such as a CD player for
reproducing a music CD, or may be a microphone.
Although the sound source device 2 is shown outside the sound expansion space 40 in FIG. 1, the
sound source device 2 may be installed in the sound expansion space 40.
For example, the sound source device 2 may be a microphone installed in the sound amplification
space 40.
The dip filter 4 is for removing a signal component of a specific frequency from the output signal
of the sound source device 2 and sending it to the amplifier 12.
The output signal of the dip filter 4 is amplified by the amplifier 12 and sent out to the speaker
13, and is amplified from the speaker 13 in the amplification space 40.
[0023]
When the loud sound space 40 has a resonant frequency, if a large amount of resonant
frequency is contained in the loud sound from the speaker 13, resonance occurs in the loud
sound space 40, and it becomes difficult to hear music and voice from the loud speaker 13.
However, in this acoustic system, if the dip filter 4 is set to an appropriate frequency
characteristic, resonance in the loudspeaker space 40 can be prevented without deteriorating the
08-05-2019
8
sound quality of the loudspeaker sound from the loudspeaker 13.
[0024]
In the present embodiment, the resonance frequency is detected in the loud sound space 40, and
among the detected resonance frequencies, the frequency to be set as the dip center frequency
for the dip filter 4 is selected. A method and apparatus for detecting a resonance frequency in the
sound amplification space 40 will be described with reference to 2 to 26.
[0025]
FIG. 2 is a schematic block diagram of a system Sa for measuring amplitude frequency
characteristics in a loudspeaker space (eg, a concert hall or gymnasium) 40.
This system Sa includes a transmitter 11 as a sound source means for emitting a measurement
signal, an amplifier 12 for inputting and amplifying the power of the signal generated by the
transmitter 11, and a speaker 13 for inputting and expanding an output signal of the amplifier
12 And a microphone 14 for receiving a loud sound emitted by the speaker 13 and a measuring
device 15 for receiving an output signal of the microphone 14. The microphone 14 may be a
noise level meter.
[0026]
The speaker 13 and the microphone 14 are disposed in the loudspeaker space 40. The
microphone 14 is disposed at a position where the reflected sound in the loud sound space 40
can be received at a sufficiently large level with respect to the direct sound from the speaker 13.
[0027]
The transmitter 11 emits a sine wave signal whose frequency changes with time as a
measurement signal. That is, the transmitter 11 transmits a sine wave sweep signal. In this sine
wave sweep signal, the level of the sine wave is constant at each time point in the frequency
sweep.
08-05-2019
9
[0028]
The measuring device 15 has a band pass filter whose center frequency changes temporally. This
band pass filter temporally changes the center frequency in response to temporal changes in the
frequency of the sine wave sweep signal emitted by the transmitter 11. Therefore, the measuring
instrument 15 can measure the amplitude characteristic of the frequency at that time by
detecting the level of the output signal of the microphone 14 through this band pass filter.
[0029]
FIG. 3 is a schematic block diagram of a system Sb for measuring the amplitude frequency
characteristic in the loudspeaker space 40. This system Sb is merely the system Sa of FIG. 2 with
the addition of a path for synthesizing a certain signal. That is, the system Sb of FIG. 3 includes a
transmitter 11, which is a sound source means for emitting a measurement signal, a mixing
device 16, an amplifier 12 which receives an output signal of the mixing device 16 and amplifies
the power of the signal. It includes a speaker 13 which receives an output signal and amplifies it,
a microphone 14 which receives a loud sound emitted by the speaker 13, and a measuring device
15 which receives an output signal of the microphone 14.
[0030]
The speaker 13 and the microphone 14 are disposed at the same position in the loudspeaker
space 40 as in the system Sa of FIG. The transmitter 11, the amplifier 12, the speaker 13, the
microphone 14 and the measuring device 15 in the system Sb of FIG. 3 are the same as these
devices in the system Sa of FIG.
[0031]
The difference between the system Sb of FIG. 3 and the system Sa of FIG. 2 is that the amplifier
12 inputs the signal from the transmitter 11 in the system Sa of FIG. 12 is the point where the
signal from the mixing device 16 is input. The mixing device 16 of FIG. 3 receives the
measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of
the microphone 14, combines (mixes) these input signals, and this combined signal (mixing)
08-05-2019
10
Output signal).
[0032]
FIG. 4 is a characteristic diagram schematically showing the amplitude frequency characteristic
of the loud sound space 40 measured by the system Sa of FIG. 2 and the amplitude frequency
characteristic of the loud sound space 40 measured by the system Sb of FIG. A curve Ca shown
by a solid line in FIG. 4 is an amplitude frequency characteristic by the system Sa of FIG. 2, and a
curve Cb shown by a broken line is an amplitude frequency characteristic by the system Sb of
FIG.
[0033]
Both the system Sa of FIG. 2 and the system Sb of FIG. 3 measure the amplitude values at a
number of frequency points. For example, in the frequency range to be measured, amplitude
values are measured at intervals of 1/192 octaves. The measured values at multiple points (a
number of frequency points) may be represented as curves Ca and Cb as amplitude frequency
characteristics of the loudspeaker space 40 without smoothing on the frequency axis, or by any
method on the frequency axis. It may be smoothed and represented by curves Ca and Cb. There
are various methods of smoothing at this time, but for example, smoothing may be performed by
moving average. For example, a moving average of nine points on the frequency axis may be
applied to measurements of a large number of frequency points. In addition, when using what
was smooth | blunted as curve Ca, it is preferable to use what was smooth | blunted also about
curve Cb. In this case, it is further preferable to obtain the curve Cb by the same smoothing
method as that for the curve Ca. For example, if the curve Ca is obtained by moving average of 9
points on the frequency axis, the curve Cb is also preferably obtained by moving average of 9
points on the frequency axis.
[0034]
The amplitude frequency characteristic of the actual curve Ca in FIG. 4 includes not only the
characteristic of the electroacoustic system by the amplifier 12, the speaker 13 and the
microphone 14, but also the characteristic of the resonance of the sound amplification space 40.
The amplitude frequency characteristics of the broken line Cb in FIG. 4 also include not only the
characteristics of the electroacoustic system of the amplifier 12, the speaker 13 and the
08-05-2019
11
microphone 14 but also the characteristics of the resonance of the loud space 40. Due to the
feedback loop in which the output signal is input to the amplifier 12 and output from the speaker
13, the resonance characteristic of the loudspeaker space 40 appears to be emphasized more
than the amplitude frequency characteristic of the real curve Ca. Further, the amplitude
frequency characteristic of broken line Cb in FIG. 4 includes a characteristic due to a feedback
loop in which the output signal of microphone 14 is input to amplifier 12 and output from
speaker 13. From the difference between the two curves (the actual curve Ca and the broken
curve Cb), it is possible to know the characteristics of the resonance of the loud space 40 and the
characteristics of the feedback.
[0035]
The frequency characteristic shown in FIG. 5 is a characteristic obtained by subtracting the
characteristic of the actual curve Ca from the characteristic of the broken curve Cb of FIG. The
frequencies showing peaks in the positive direction in the characteristic curve Db of FIG. 5 are
the frequency f1, the frequency f21 and the frequency f3. Frequencies showing peaks in these
positive directions are likely to be resonance frequencies or feedback frequencies. The number of
resonance frequencies in the sound expansion space 40 is not limited to one, and may be plural.
Also, the number of feedback frequencies is not limited to one, and is often more than one.
Among the frequencies f1, f21 and f3, one or more frequencies may be resonance frequencies,
and one or more frequencies may be feedback frequencies.
[0036]
The feedback frequency referred to here is the feedback frequency in the system Sb of FIG. The
feedback loop is constituted by a path of an electrical system from the microphone 14 to the
speaker 13 and a path of an acoustic system from the speaker 13 to the microphone 14. The
microphone 14 is a measurement microphone for measuring the acoustic characteristic of the
sound expansion space 40. Therefore, for example, it is not necessary to set this feedback
frequency as a dip frequency in a dip filter in an electroacoustic system which is always installed
in the sound amplification space 40. Therefore, it is desirable to know which one of the
frequency f1, the frequency f21 and the frequency f3 in FIG. 5 is the resonance frequency. That
is, it is desirable that the resonance frequency can be detected separately from the feedback
frequency. For that purpose, it is effective to perform measurement by the system Sc shown in
FIG.
08-05-2019
12
[0037]
FIG. 6 is a schematic block diagram of systems Sc1 and Sc2 for measuring the amplitude
frequency characteristic in the loud sound space 40, wherein (a) shows the system Sc1 and (b)
shows the system Sc2. The systems Sc1 and Sc2 are obtained by adding the delay device 17 to
the system Sb of FIG.
[0038]
That is, in the systems Sc1 and Sc2 of FIG. 6, a transmitter 11 serving as a sound source means
for emitting a measurement signal, a mixing device 16, an amplifier 12 for power amplifying the
signal, and a speaker for inputting and amplifying the output signal of the amplifier 12 13, a
microphone 14 for receiving a loud sound emitted by the speaker 13, a measuring device 15 for
receiving an output signal of the microphone 14, and a delay device 17.
[0039]
The speaker 13 and the microphone 14 are disposed at the same position in the loudspeaker
space 40 as in the system Sa of FIG.
The transmitter 11, the amplifier 12, the speaker 13, the microphone 14 and the measuring
device 15 in the systems Sc1 and Sc2 of FIG. 6 are the same as these devices in the system Sa of
FIG. In these points, the systems Sc1 and Sc2 of FIG. 6 are common to the system Sb of FIG.
[0040]
The differences between the systems Sc1 and Sc2 of FIG. 6 and the system Sb of FIG. 3 are as
follows. That is, in the system Sb of FIG. 3, the mixing device 16 receives the measurement signal
(sine wave sweep signal) from the transmitter 11 and the output signal of the microphone 14
and combines (mixes) these input signals. The synthesized signal is sent to the amplifier 12.
[0041]
On the other hand, in the system Sc1 of FIG. 6A, after delaying the composite signal of the
measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of
08-05-2019
13
the microphone 14 by the delay device 17, It is input to the amplifier 12.
[0042]
Further, in the system Sc2 of FIG. 6B, the mixing device 16 mixes the measurement signal (sine
wave sweep signal) from the transmitter 11 and the delay signal obtained by delaying the output
signal of the microphone 14 by the delay device 17. These signals are input, synthesized (mixed)
these input signals, and sent out to the amplifier 12.
[0043]
In any of the systems (systems Sc1 and Sc2), the speaker 13 amplifies the measurement signal
and the delay signal obtained by delaying the output signal of the microphone 14 by the delay
device 17.
[0044]
FIG. 7 is a characteristic diagram schematically showing the amplitude frequency characteristic
of the loud sound space 40 measured by the system Sa of FIG. 2 and the amplitude frequency
characteristic of the loud sound space 40 measured by the system Sc1 or the system Sc2 of FIG.
is there.
Strictly speaking, although the amplitude frequency characteristic measured by the system Sc1 in
FIG. 6A and the amplitude frequency characteristic measured by the system Sc2 in FIG. 6B are
not identical, here, these are to be distinguished. I will explain without.
[0045]
A curve Ca shown by a solid line in FIG. 7 is an amplitude frequency characteristic by the system
Sa of FIG. 2, and a curve Cc shown by a broken line is an amplitude frequency characteristic by
the systems Sc1 and Sc2 of FIG.
[0046]
The systems Sc1 and Sc2 of FIG. 6 also measure amplitude values at a large number of frequency
points, similarly to the system Sa of FIG. 2 and the system Sb of FIG.
08-05-2019
14
For example, in the frequency range to be measured, amplitude values are measured at intervals
of 1/192 octaves.
The measured values at multiple points (a number of frequency points) may be represented as
curves Ca and Cc as amplitude frequency characteristics of the loudspeaker space 40 without
smoothing on the frequency axis, or by any method on the frequency axis. It may be smoothed
and represented on curves Ca and Cc.
There are various methods of smoothing at this time, but for example, smoothing may be
performed by moving average. For example, a moving average of nine points on the frequency
axis may be applied to measurements of a large number of frequency points. In addition, when
using what was smooth | blunted as curve Ca, it is preferable to use what was smooth | blunted
also about curve Cc. In this case, it is further preferable to obtain the curve Cc by the same
smoothing method as that for the curve Ca.
[0047]
As described above, the amplitude frequency characteristic of the actual curve Ca includes not
only the characteristic of the electroacoustic system by the amplifier 12, the speaker 13 and the
microphone 14, but also the characteristic of the resonance of the loud space 40.
[0048]
The systems Sc1 and Sc2 of FIG. 6 include a feedback loop in which a delay signal obtained by
delaying the output signal of the microphone 14 is input to the amplifier 12 and output from the
speaker 13.
Not only the characteristic of the electroacoustic system by the amplifier 12, the speaker 13 and
the microphone 14 appears in the amplitude frequency characteristic of the broken curve Cc in
FIG. 7, but also the characteristic of the resonance of the loudspeaker space 40 is the amplitude
frequency of the real curve Ca. It appears emphasized more than the characteristics. Further, the
amplitude frequency characteristic of broken line Cc in FIG. 7 includes this feedback
characteristic due to the feedback loop in which the delay signal obtained by delaying the output
signal of microphone 14 is inputted to amplifier 12 and outputted from speaker 13. ing.
08-05-2019
15
[0049]
As described above, the broken curve Cc in FIG. 7 is common to the broken curve Cb in FIG. 4 in
that the resonance characteristic of the loudspeaker space 40 is greatly emphasized and appears
and the characteristic due to the feedback is also shown. However, since the systems Sc1 and Sc2
of FIG. 6 have the delay device 17, the configuration of the feedback loop of the systems Sc1 and
Sc2 of FIG. 6 is not the same as the configuration of the feedback loop of the system Sb of FIG.
Therefore, the characteristic by feedback shown in broken curve Cc in FIG. 7 is different from the
characteristic by feedback shown in broken curve Cb in FIG.
[0050]
The frequency characteristic shown in FIG. 8 is a characteristic obtained by subtracting the
characteristic of the actual curve Ca from the characteristic of the broken curve Cc of FIG. The
frequencies showing peaks in the positive direction in FIG. 8 are the frequency f1, the frequency
f22 and the frequency f3. Frequencies showing peaks in these positive directions are likely to be
resonant frequencies or feedback frequencies.
[0051]
Here, the characteristics shown in FIG. 5 and the characteristics shown in FIG. 8 are compared.
The frequency characteristics of FIG. 5 show peaks in the positive direction at frequency f1,
frequency f21 and frequency f3, and the frequency characteristics of FIG. 8 show peaks in the
positive direction at frequency f1, frequency f22 and frequency f3. The frequency f1 and the
frequency f3 are frequencies showing a peak in the positive direction in common in the
frequency characteristics of both figures. The frequency f21 is a frequency that exhibits a peak in
the positive direction only in the frequency characteristic of FIG. The frequency f22 is a
frequency that exhibits a peak in the positive direction only in the frequency characteristic of
FIG.
[0052]
08-05-2019
16
As described above, the feedback characteristic shown in broken line Cc in FIG. 7 is different
from the feedback characteristic shown in broken line Cb in FIG. Therefore, it can be considered
that the frequency showing a peak in the positive direction due to feedback in the frequency
characteristic of FIG. 5 is different from the frequency showing a peak in the positive direction
due to feedback in the frequency characteristic of FIG. .
[0053]
On the other hand, it can be considered that the frequency showing a peak in the positive
direction due to the resonance of the sound amplification space 40 appears commonly in the
frequency characteristic of FIG. 5 and in the frequency characteristic of FIG.
[0054]
From the above, the frequencies f1 and f3 are resonance frequencies of the loudspeaker space
40, the frequency f21 is a feedback frequency based on the feedback loop of the system Sb of
FIG. 3, and the frequency f22 is a feedback of the systems Sc1 and Sc2 of FIG. It can be thought
of as a loop based feedback frequency.
[0055]
Therefore, for example, in the acoustic system of FIG. 1, the frequency f1 and the frequency f3
may be set as the center frequency of dip to the dip filter 4.
[0056]
In the above example, the delay device is not provided in the system Sb of FIG.
However, it can be considered that the output signal of the microphone 14 is delayed by 0
seconds and sent to the mixing device 16.
Then, the difference between the system Sb of FIG. 3 and the systems Sc1 and Sc2 of FIG. 6 can
be considered to be the difference of the delay time with respect to the output signal of the
microphone 14.
That is, both in the system Sb of FIG. 3 and in the systems Sc1 and Sc2 of FIG. 6, the output
08-05-2019
17
signal of the microphone 14 is delayed before being sent to the mixing device 16. It can be
considered that the three systems Sb and the systems Sc1 and Sc2 of FIG. 6 are different.
[0057]
Furthermore, if the delay devices 17 in the systems Sc1 and Sc2 of FIG. 6 can set delay times
arbitrarily in a predetermined time range, the systems Sc1 and Sc2 of FIG. 6 can be used without
using the system Sb of FIG. The resonant frequency can be detected separately from the feedback
frequency. That is, the measurement in the systems Sc1 and Sc2 of FIG. 6 is performed twice.
However, in the two measurements, the delay times set in the delay device 17 must be made
identical. For example, in the first measurement, the delay time may be 1 ms, and in the second
measurement, the delay time may be 2 ms. Also, for example, the delay time may be 0 ms in the
first measurement, and may be 1 ms in the second measurement.
[0058]
In the systems Sc1 and Sc2 of FIG. 6, when the delay time set in the delay device 17 is changed,
the configuration of the feedback loop is also changed. Therefore, as described above, the
resonance frequency can be detected separately from the feedback frequency also by performing
the measurement in the system Sa of FIG. 2 once and the measurement in the systems Sc1 and
Sc2 of FIG. 2 twice. is there.
[0059]
The following method can be taken as to how much difference (time difference) is to be provided
in the delay time between the first measurement and the second measurement. That is, a time
difference which does not match the period of the frequency (for example, frequency 1) showing
a peak in the positive direction in FIG. 5 is provided.
[0060]
For example, it is assumed that 200 Hz is the feedback frequency in the first measurement. In
such a case, if the time difference between the delay time in the first measurement and the delay
08-05-2019
18
time in the second measurement is 5 ms, which is the cycle of the 200 Hz sound wave, 200 Hz is
also the feedback frequency in the second measurement. I will. As a result, it becomes impossible
to determine whether 200 Hz is the resonance frequency or the feedback frequency.
[0061]
Therefore, after detecting the frequencies that may be resonant frequencies (frequency f1,
frequency f21 and frequency f3 in FIG. 5) by the first measurement, whether these frequencies
are resonant frequencies or feedback frequency by the second measurement In order to
determine whether it is the case, it is preferable to provide a time difference between the delay
time in the first measurement and the delay time in the second measurement that does not at
least coincide with the period of these frequencies. For example, it is preferable to provide a time
difference of 1⁄4 of the period of these frequencies.
[0062]
FIG. 9 is a schematic block diagram of systems Sd1 and Sd2 including detection devices 201 and
202 as one embodiment of the resonance frequency detection device according to the present
invention, and FIG. 9 (a) shows the detection device 201 and system Sd1. FIG. 9B shows a
detection device 202 and a system Sd2.
[0063]
In the systems Sd1 and Sd2, the detection devices 201 and 202, an amplifier 12 for inputting
and amplifying the power of signals emitted by the detection devices 201 and 202, a speaker 13
for inputting and expanding an output signal of the amplifier 12, and a speaker 13 emit And a
microphone 14 for receiving a loud sound.
The detection devices 201 and 202 receive the output signal of the microphone 14. The speaker
13 and the microphone 14 are disposed in a loudspeaker space (for example, a concert hall or a
gymnasium) 40. The microphone 14 is disposed at a position where the reflected sound in the
loud sound space 40 can be received at a sufficiently large level with respect to the direct sound
from the speaker 13.
[0064]
08-05-2019
19
The detection devices 201 and 202 include a transmission unit 21, a measurement / control unit
25, a mixing unit 26, an opening / closing unit 27, and a delay device 28 of variable delay time
type. The transmission unit 21 functions as a sound source unit that emits a measurement signal.
The measurement / control unit 25 functions as a control unit that controls each unit in the
detection devices 201 and 202, and also functions as a measurement unit that measures the
frequency characteristic. Also, the delay device 28 functions as a delay means. Further, the signal
switching means is constituted by the mixing unit 26, the opening / closing unit 27 and the delay
device 28.
[0065]
In the systems Sd1 and Sd2, in the detection devices 201 and 202, the measurement / control
unit 25 controls the transmission unit 21 to output a measurement signal from the transmission
unit 21. The measurement signal is a sine wave signal whose frequency changes with time, that
is, a sine wave sweep signal. In this sine wave sweep signal, the level of the sine wave is constant
at each point in the frequency sweep.
[0066]
In the detection device 201 of FIG. 6A, the mixing unit 26 combines (mixes) the signal from the
transmission unit 21 and the signal from the opening / closing unit 27, and outputs the
combined signal (mixing signal). . The synthesized signal is delayed by the delay device 28 and
then input to the amplifier 12, amplified in power, input to the speaker 13, and emitted from the
speaker 13 to the sound-scaling space 40 as sound. The sound in the loud sound space 40 is
received by the microphone 14, and the output signal of the microphone 14 is input to the
detection device 201. In the detection device 201, the output signal of the microphone 14 is
branched to the measurement / control unit 25 and the opening / closing unit 27 and sent out.
[0067]
On the other hand, in the detection device 202 of FIG. 6B, the mixing unit 26 combines (mixes)
the signal from the transmission unit 21 and the signal from the opening / closing unit 27 and
mixes the signal (mixing signal). Output. The output signal of the mixing unit 26 is power-
08-05-2019
20
amplified by the amplifier 12 and input to the speaker 13, and is emitted from the speaker 13 as
a loud sound to the loud space 40. The sound in the loud sound space 40 is received by the
microphone 14, and the output signal of the microphone 14 is input to the detection device 202.
In the detection device 202, the output signal of the microphone 14 is branched and sent out to
the measurement / control unit 25 and the delay device 28. The output signal of the delay device
28 is sent to the open / close unit 27.
[0068]
In the detection devices 201 and 202, the measurement / control unit 25 has a band pass filter
whose center frequency changes temporally. The band pass filter temporally changes the center
frequency in response to the temporal change of the frequency of the sine wave sweep signal
transmitted by the transmission unit 21. Therefore, the measurement / control unit 25 can
measure the amplitude characteristic of the frequency at that time by detecting the level of the
output signal of the microphone 14 through this band pass filter.
[0069]
The measurement and control unit 25 can control the opening and closing of the opening and
closing unit 27. Therefore, the open / close unit 27 can be in the "open" state, and only the
measurement signal from the transmission unit 21 can be amplified from the speaker 13.
Alternatively, the open / close unit 27 can be in the "closed" state. And the delayed signal of the
output signal of the microphone 14 can be amplified from the speaker 13.
[0070]
Further, the measurement / control unit 25 can set at least two kinds of delay times in the delay
device 28.
[0071]
For example, the delay time of the delay device 28 may be arbitrarily set to one of 0 ms and 1
ms, or may be set to any one of 1 ms and 2 ms. It may be possible.
08-05-2019
21
In addition, any of 0 ms, 1 ms and 2 ms may be set arbitrarily.
[0072]
In the systems Sd1 and Sd2 of FIG. 9, when the open / close unit 27 is in the “open” state, the
same amplitude frequency characteristics as those measured by the system Sa of FIG. 2 can be
measured.
[0073]
If the open / close unit 27 is closed and the delay time of the delay unit 28 is set to 0 msec, the
same amplitude frequency characteristic as that measured by the system Sb of FIG. 3 can be
measured.
[0074]
If the open / close unit 27 is in the “closed” state and the delay time of the delay device 28 is
set to a predetermined time other than 0 (for example, 1 ms), the delay device 17 of the systems
Sc1 and Sc2 of FIG. It is possible to measure the same amplitude frequency characteristics as
when measuring by setting sec) as the delay time.
[0075]
As described above, the resonance frequency of the loudspeaker space 40 can be detected from
the amplitude frequency characteristic measured in this manner, as distinguished from the
feedback frequency.
All operations for detecting the resonance frequency from the measured amplitude frequency
characteristics are performed by the measurement / control unit 25.
[0076]
In the above, the procedure of detecting the resonance frequency by setting the delay time of the
delay device 28 to 0 msec and a predetermined time other than 0 (for example, 1 msec) in the
systems Sd1 and Sd2 has been described.
08-05-2019
22
However, in the systems Sd1 and Sd2, the resonance frequency is detected by setting the delay
time of the delay device 28 to a first delay time other than 0 (for example, 1 ms) and a second
delay time other than 0 (for example 2 ms) You can also
The point is that the delay time can be switched in two ways. Then, one of the two delay times
may be 0 msec, or both may be non-zero times.
[0077]
FIG. 10 is a diagram showing an example of a configuration that can be adopted as the delay
device 28 in the detection devices 201 and 202 of FIG. As the delay device 28 (delay device of
variable delay time type) of FIG. 9, a delay device 28a as shown in FIG. 10A may be adopted, or a
delay device 28b as shown in FIG. 10B is adopted. May be
[0078]
The delay device 28a shown in FIG. 10A includes a changeover switch 29 and a delay element 50
fixed for a predetermined time (for example, 1 millisecond) other than zero. By switching and
controlling the changeover switch 29, the delay time of the delay device 28a can be switched
between 0 msec and the predetermined time (for example, 1 msec).
[0079]
The delay device 28 b shown in FIG. 10B includes a delay element 51 that can set the delay time
arbitrarily within a predetermined time range. For example, the delay time of the delay element
51 may be switched between 0 msec and 1 msec, or may be switched between 1 msec and 2
msec.
[0080]
The apparatus and method for detecting the resonance frequency from the feedback frequency
by delaying the output signal of the microphone 14 disposed in the sound amplification space 40
has been described above.
08-05-2019
23
[0081]
Next, an apparatus and method for detecting the resonance frequency from the feedback
frequency by inverting the phase of the output signal of the microphone 14 disposed in the
sound amplification space 40 will be described.
[0082]
FIG. 11 is a schematic block diagram of systems Se1 and Se2 for measuring the amplitude
frequency characteristic in the loud sound space 40, the system Se1 is shown in FIG. 11 (a) and
the system Se in FIG. 11 (b) Se2 is shown.
[0083]
The systems Se1 and Se2 are obtained by merely adding the phase reversing device 19 to the
system Sb of FIG.
That is, the systems Se1 and Se2 in FIG. 11 are a transmitter 11 as a sound source means for
emitting a measurement signal, a mixing device 16, an amplifier 12 for power amplifying the
signal, and a speaker for inputting and amplifying the output signal of this amplifier 12 13, a
microphone 14 for receiving a loud sound emitted by the speaker 13, a measuring device 15 for
receiving an output signal of the microphone 14, and a phase inverting device 19 for inverting
and outputting the phase of the input signal.
[0084]
The speaker 13 and the microphone 14 are disposed at the same position in the loudspeaker
space 40 as in the system Sa of FIG.
The transmitter 11, the amplifier 12, the speaker 13, the microphone 14 and the measuring
device 15 in the systems Se1 and Se2 in FIG. 11 are the same as those in the system Sa in FIG.
In these points, the systems Se1 and Se2 of FIG. 11 are common to the system Sb of FIG.
08-05-2019
24
[0085]
The differences between the systems Se1 and Se2 of FIG. 11 and the system Sb of FIG. 3 are as
follows. That is, in the system Sb of FIG. 3, the mixing device 16 receives the measurement signal
(sine wave sweep signal) from the transmitter 11 and the output signal of the microphone 14
and combines (mixes) these input signals. Then, they are sent to the amplifier 12.
[0086]
On the other hand, in the system Se1 of FIG. 11 (a), the mixing device 16 performs phase
inversion of the composite signal of the measurement signal (sine wave sweep signal) from the
transmitter 11 and the output signal of the microphone 14. , And phase-inverted, and then sent
to the amplifier 12.
[0087]
Further, in the system Se2 of FIG. 11B, the mixing device 16 mixes the measurement signal (sine
wave sweep signal) from the transmitter 11 and the output signal of the phase inversion device
19 to which the output signal of the microphone 14 is input. These signals are input, synthesized
(mixed) these input signals, and sent out to the amplifier 12.
[0088]
In any of the systems (systems Se1 and Se2), the speaker 13 amplifies the measurement signal
and the phase inversion signal obtained by inverting the phase of the output signal of the
microphone 14.
[0089]
FIG. 12 is a characteristic diagram schematically showing the amplitude frequency characteristic
of the loud space 40 measured by the system Sa of FIG. 2 and the amplitude frequency
characteristic of the loud space 40 measured by the systems Se1 and Se2 of FIG. .
Strictly speaking, although the amplitude frequency characteristics measured by the system Se1
in FIG. 11A and the amplitude frequency characteristics measured by the system Se2 in FIG. 11B
08-05-2019
25
are not identical, here, these are to be distinguished. I will explain without.
A curve Ca shown by a solid line in FIG. 12 is an amplitude frequency characteristic by the
system Sa of FIG. 2, and a curve Ce shown by a broken line is an amplitude frequency
characteristic by the systems Se1 and Se2 of FIG.
[0090]
The systems Se1 and Se2 of FIG. 11 also measure amplitude values at a large number of
frequency points, similarly to the system Sa of FIG. 2 and the system Sb of FIG.
For example, in the frequency range to be measured, amplitude values are measured at intervals
of 1/192 octaves. The measured values at multiple points (a number of frequency points) may be
represented as curves Ca and Ce as amplitude frequency characteristics of the loudspeaker space
40 without smoothing on the frequency axis, or by any method on the frequency axis. It may be
smoothed and represented by curves Ca and Ce. There are various methods of smoothing at this
time, but for example, smoothing may be performed by moving average. For example, a moving
average of nine points on the frequency axis may be applied to measurements of a large number
of frequency points. In addition, when using what was smooth | blunted as curve Ca, it is
preferable to use what was smooth | blunted also about curve Ce. In this case, it is further
preferable to obtain the curve Ce by the same smoothing method as that for the curve Ca.
[0091]
As described above, the amplitude frequency characteristic of the actual curve Ca includes not
only the characteristic of the electroacoustic system by the amplifier 12, the speaker 13 and the
microphone 14, but also the characteristic of the resonance of the loud space 40.
[0092]
The systems Se1 and Se2 of FIG. 11 include a feedback loop in which a phase inversion signal of
the output signal of the microphone 14 is input to the amplifier 12 and output from the speaker
13.
08-05-2019
26
Therefore, not only the characteristic of the electroacoustic system by the amplifier 12, the
speaker 13 and the microphone 14 appears in the amplitude frequency characteristic of the
broken curve Ce in FIG. 12, but also the characteristic of the resonance of the loud sound space
40 is the real curve Ca. It appears emphasized more than the amplitude frequency characteristic.
Further, the amplitude frequency characteristic of broken line Ce in FIG. 12 includes this
feedback characteristic due to a feedback loop in which the phase inversion signal of the output
signal of microphone 14 is inputted to amplifier 12 and outputted from speaker 13. .
[0093]
As described above, the broken curve Ce in FIG. 12 is common to the broken curve Cb in FIG. 4 in
that the resonance characteristic of the loudspeaker space 40 is greatly emphasized and appears
and the characteristic due to feedback is also shown. However, since the systems Se1 and Se2 of
FIG. 11 have the phase reversing device 19, the configuration of the feedback loop of the systems
Se1 and Se2 of FIG. 11 is not the same as the configuration of the feedback loop of the system Sb
of FIG. Therefore, the characteristic due to feedback appearing in broken curve Ce in FIG. 12 is
different from the characteristic due to feedback appearing in broken curve Cb in FIG.
[0094]
The frequency characteristic shown in FIG. 13 is a characteristic obtained by subtracting the
characteristic of the actual curve Ca from the characteristic of the broken curve Ce of FIG. The
frequencies showing peaks in the positive direction in FIG. 13 are the frequency f1, the
frequency f23 and the frequency f3. Frequencies showing peaks in these positive directions are
likely to be resonant frequencies or feedback frequencies.
[0095]
Here, the characteristics shown in FIG. 5 and the characteristics shown in FIG. 13 are compared.
The frequency characteristics of FIG. 5 show peaks in the positive direction at frequency f1,
frequency f21 and frequency f3, and the frequency characteristics of FIG. 13 show peaks in the
positive direction at frequency f1, frequency f23 and frequency f3. The frequency f1 and the
frequency f3 are frequencies showing a peak in the positive direction in common in the
frequency characteristics of both figures. The frequency f21 is a frequency that exhibits a peak in
the positive direction only in the frequency characteristic of FIG. The frequency f23 is a
08-05-2019
27
frequency that exhibits a peak in the positive direction only in the frequency characteristics of
FIG.
[0096]
The configuration of the feedback loop of the systems Se1 and Se2 of FIG. 11 is different from
the configuration of the feedback loop of the system Sb of FIG. Therefore, the characteristic due
to feedback appearing in broken curve Ce in FIG. 12 is different from the characteristic due to
feedback appearing in broken curve Cb in FIG. Therefore, it can be considered that the frequency
showing a peak in the positive direction due to feedback in the frequency characteristic of FIG. 5
is different from the frequency showing a peak in the positive direction due to feedback in the
frequency characteristic of FIG. .
[0097]
On the other hand, it can be considered that the frequency showing a peak in the positive
direction due to the resonance of the sound amplification space 40 appears in common in both
the frequency characteristic of FIG. 5 and the frequency characteristic of FIG.
[0098]
From the above, the frequencies f1 and f3 are resonance frequencies of the loudspeaker space
40, the frequency f21 is a feedback frequency based on the feedback loop of the system Sb of
FIG. 3, and the frequency f23 is a feedback of the systems Se1 and Se2 of FIG. It can be thought
of as a loop based feedback frequency.
[0099]
Therefore, for example, in the acoustic system of FIG. 1, the frequency f1 and the frequency f3
may be set as the center frequency of dip to the dip filter 4.
[0100]
FIG. 14 is a schematic block diagram of systems Sf1 and Sf2 including detection devices 301 and
302 which are one embodiment of a resonance frequency detection device according to the
present invention, and FIG. 14 (a) shows detection device 301 and system Sf1. The detection
device 302 and the system Sf2 are shown in FIG.
08-05-2019
28
[0101]
The systems Sf1 and Sf2 are provided with detection devices 301 and 302, an amplifier 12 for
inputting and amplifying the power of signals emitted by the detection devices 301 and 302, a
speaker 13 for inputting and amplifying an output signal of the amplifier 12, and a speaker 13
And a microphone 14 for receiving a loud sound.
The detection devices 301 and 302 receive the output signal of the microphone 14.
The speaker 13 and the microphone 14 are disposed in a loudspeaker space (for example, a
concert hall or a gymnasium) 40.
The microphone 14 is disposed at a position where the reflected sound in the loud sound space
40 can be received at a sufficiently large level with respect to the direct sound from the speaker
13.
[0102]
The detection devices 301 and 302 each include a transmission unit 21, a measurement / control
unit 25, a mixing unit 26, an opening / closing unit 27, a changeover switch 31, and a phase
reversing device 32.
The transmission unit 21 functions as a sound source unit that emits a measurement signal. The
measurement / control unit 25 functions as a control unit that controls each unit in the detection
devices 301 and 302, and also functions as a measurement unit that measures the frequency
characteristic. In addition, the phase inversion device 32 functions as phase inversion means.
Further, the signal switching means is constituted by the mixing unit 26, the opening / closing
unit 27, the changeover switch 31, and the phase reversing device 32.
[0103]
In the systems Sf1 and Sf2, in the detection devices 301 and 302, the measurement / control unit
08-05-2019
29
25 controls the transmission unit 21 to output a measurement signal from the transmission unit
21. The measurement signal is a sine wave signal whose frequency changes with time, that is, a
sine wave sweep signal. In this sine wave sweep signal, the level of the sine wave is constant at
each point in the frequency sweep.
[0104]
The mixing unit 26 combines (mixes) the signal from the transmission unit 21 and the signal
from the opening / closing unit 27 and outputs the combined signal (mixing signal). The signal
input to the amplifier 12 is power-amplified, input to the speaker 13, and emitted from the
speaker 13 as a loud sound to the loud space 40. The sound in the loud sound space 40 is
received by the microphone 14, and the output signal of the microphone 14 is input to the
detection devices 301 and 302.
[0105]
In the detection device 301 of FIG. 14A, the output signal of the microphone 14 is branched to
the measurement / control unit 25 and the switch 27, and is sent out. Further, the output signal
of the mixing unit 26 is branched and sent out to the phase inverting device 32 and the
changeover switch 31. The output signal of the phase inverter 32 is also sent to the changeover
switch 31. Then, the signal from the changeover switch 31 is input to the amplifier 12.
[0106]
In the detection device 302 of FIG. 14B, the output signal of the microphone 14 is branched and
sent out to the measurement / control unit 25, the phase inversion device 32, and the
changeover switch 31. The output signal of the phase inverter 32 is sent to the changeover
switch 31. The changeover switch 31 is connected to the opening / closing unit 27. Then, the
output signal of the mixing unit 26 is input to the amplifier 12.
[0107]
The measurement / control unit 25 of the detection devices 301 and 302 has a band pass filter
08-05-2019
30
whose center frequency changes temporally. The band pass filter temporally changes the center
frequency in response to the temporal change of the frequency of the sine wave sweep signal
transmitted by the transmission unit 21. Therefore, the measurement / control unit 25 can
measure the amplitude characteristic of the frequency at that time by detecting the level of the
output signal of the microphone 14 through this band pass filter.
[0108]
The measurement and control unit 25 can control the opening and closing of the opening and
closing unit 27. Therefore, the open / close unit 27 can be in the "open" state, and only the
measurement signal from the transmission unit 21 can be amplified from the speaker 13.
Alternatively, the open / close unit 27 can be in the "closed" state. And the output signal of the
microphone can be amplified from the speaker 13.
[0109]
In addition, the measurement / control unit 25 can control the state of the changeover switch 31.
Therefore, whether the output signal of the microphone 14 is amplified from the speaker 13
without inverting the phase, or the output signal of the microphone 14 is inverted by passing the
phase inverting device 32 and then amplified from the speaker 13 It can be selected.
[0110]
When the open / close unit 27 is in the “open” state, the same amplitude frequency
characteristic as that measured by the system Sa in FIG. 2 can be measured.
[0111]
When the state of the changeover switch 31 is set so that the open / close unit 27 is in the
“closed” state and the speaker 13 is made to louden without inverting the phase of the output
signal of the microphone 14, the same as the system Sb of FIG. Amplitude frequency
characteristics can be measured.
[0112]
When the state of the changeover switch 31 is set so that the open / close unit 27 is in the
“closed” state and the output signal of the microphone 14 is phase-inverted and then the
08-05-2019
31
speaker 13 is loudened, the systems Se1 and Se2 in FIG. Similar amplitude frequency
characteristics can be measured.
[0113]
As described above, the resonance frequency of the loudspeaker space 40 can be detected from
the amplitude frequency characteristic measured in this manner, as distinguished from the
feedback frequency.
All operations for detecting the resonance frequency from the measured amplitude frequency
characteristics are performed by the measurement / control unit 25.
[0114]
The apparatus and method for detecting the resonance frequency from the feedback frequency
by inverting the phase of the output signal from the microphone 14 disposed in the sound
amplification space 40 has been described above.
[0115]
In the above-described apparatus and method (the apparatus and method described with
reference to FIGS. 1 to 14), the transmitter or the transmitter transmits the sine wave sweep
signal as the measurement signal.
However, various signals can be used as the measurement signal without being limited to the
sine wave sweep signal.
For example, it is also possible to use a noise signal having a component within a predetermined
frequency width and whose center frequency sweeps.
In this case, the frequency width is preferably 1/3 octave or less. Further, it is more preferable to
set it to 1/6 octave or less. Also, for example, pink noise can be used as the measurement signal.
In this case, of course, the measuring instrument (measuring means) does not have to have a
08-05-2019
32
band pass filter whose center frequency changes temporally.
[0116]
Next, an apparatus and method for detecting a resonance frequency by outputting a reference
frequency signal from a speaker disposed in a sound expansion space will be described.
[0117]
FIG. 15 is a schematic block diagram of a system and a detection device (resonance frequency
detection device) for detecting a resonance frequency in a sound amplification space (for
example, a concert hall or a gymnasium) 40.
[0118]
The system Sg shown in FIG. 15 includes a transmitter 111 which is a sound source means for
emitting a measurement signal, an amplifier 12 for inputting and amplifying the power of a
signal generated by the transmitter 111, and an output signal of the amplifier 12 for
amplification. A speaker 13, a microphone 14 for receiving a loud sound emitted by the speaker
13, and a measurement / control unit 115 for inputting an output signal of the microphone 14
are provided.
The microphone 14 may be a noise level meter.
The measurement / control unit 115 controls the transmitter 111. That is, the frequency of the
measurement signal output from the transmitter 111 and the time interval of the measurement
signal can be controlled. The measurement / control unit 115 also functions as a measurement
unit that measures the attenuation characteristic of the output signal of the microphone 14. The
transmitter 111 and the measurement / control unit 115 constitute a detection device 400.
[0119]
The speaker 13 and the microphone 14 are disposed in the loudspeaker space 40. The
microphone 14 is disposed at a position where the reflected sound in the loud sound space 40
can be received at a sufficiently large level with respect to the direct sound from the speaker 13.
08-05-2019
33
[0120]
The measurement signal output from the transmitter 111 of the system Sg is a signal in which
the reference frequency signal is intermittently repeated plural times. The reference frequency
signal here is a sine wave signal of a specific frequency or a signal having a component within a
predetermined frequency width centered on the specific frequency. The signal having a
component in a predetermined frequency width centered on a specific frequency is, for example,
a noise signal having a frequency component of 1/3 octave width centered on 200 Hz. When
such a reference frequency signal is used, it becomes less susceptible to noise such as
background noise, and reliable measurement becomes possible.
[0121]
FIG. 16 is a diagram showing the signal levels of the measurement signal described above on a
time axis. For example, a 200 Hz sine wave, which is a specific frequency, is output for 0.1
seconds and then output again for 0.1 seconds with a time interval of 0.9 seconds, and further
for 0.9 seconds. The output is sustained for 0.1 seconds again at intervals. In other words, a 200
Hz sine wave that lasts for 0.1 seconds three times intermittently at one second intervals is
output.
[0122]
As shown in FIG. 16, in this embodiment, a 200 Hz sine wave lasting for 0.1 seconds is output a
plurality of times at equal time intervals, but it is not always necessary to output at equal time
intervals. Absent. For example, a sine wave of a specific frequency lasting for a predetermined
time may be output a plurality of times at random time intervals.
[0123]
FIG. 17 is a diagram showing the sound pressure level measured by the microphone 14 on the
time axis. Three peak points are generated at one second intervals so as to be synchronized with
the measurement signal shown in FIG. However, the sound pressure level decays quickly. As
08-05-2019
34
described above, when the sound pressure level decays quickly in the loudspeaker space, it is
considered that the specific frequency (200 Hz) of the measurement signal is not the resonance
frequency.
[0124]
FIG. 18 is a diagram showing the sound pressure level measured by the microphone 14 on the
time axis when the measurement signal having the specific frequency of 250 Hz is output from
the speaker 13 of the system Sg of FIG. A reference frequency signal having a specific frequency
of 250 Hz is output continuously for 0.1 seconds from the transmitter 111, and then output for
0.1 second again with a time interval of 0.9 seconds, and further 0 With a time interval of 9
seconds, output is continued for 0.1 seconds again. That is, a 250 Hz sine wave which is
intermittently held for 3 seconds at 0.1 second intervals is outputted.
[0125]
As understood from FIG. 18, at the sound pressure level measured in the loud sound space 40,
three peak points occur at one second intervals so as to be synchronized with the measurement
signal. The sound pressure level decays slowly. As described above, when the sound pressure
level decays slowly in the loud sound space 40, it is considered that the specific frequency (250
Hz) of the measurement signal may be the resonance frequency of the loud sound space 40.
[0126]
As described above, if the resonance frequency is determined from the attenuation
characteristics of the sound pressure level in the loud sound space 40, the reference frequency
signal does not have to be emitted from the speaker 13 a plurality of times. For example, a
reference frequency signal lasting several seconds can be emitted from the speaker 13 only once,
and the resonance frequency can be determined from the attenuation characteristics of the
sound pressure level in the loud space 40. For example, it can also be judged by whether it
attenuates more slowly than a predetermined speed.
[0127]
08-05-2019
35
In addition, in order to determine whether the attenuation of the sound pressure level in the loud
sound space 40 is gradual or rapid, for example, in the diagram in which the sound pressure
level is represented on the time axis as shown in FIG. You may judge by calculating the area of
the area enclosed by the level curve. That is, if the area is small, the attenuation of the sound
pressure level is rapid, and if the area is large, it is determined that the attenuation of the sound
pressure level is slow.
[0128]
FIG. 19 is a diagram showing the sound pressure level measured by the microphone 14 on the
time axis when the measurement signal having the specific frequency of 300 Hz is output from
the speaker 13 of the system Sg of FIG. A reference frequency signal having a specific frequency
of 300 Hz is output continuously for 0.1 seconds from the transmitter 111, and then output for
0.1 second again with a time interval of 0.9 seconds, and further 0 With a time interval of 9
seconds, output is continued for 0.1 seconds again. That is, a 300 Hz sine wave that is
intermittently held for 3 seconds at 0.1 second intervals and output for 0.1 second is output.
[0129]
As understood from FIG. 19, at the sound pressure level measured in the loud sound space 40,
three peak points occur at one second intervals so as to be synchronized with the measurement
signal. The sound pressure level decays slowly. Moreover, the attenuation from the second peak
is slower than the attenuation from the first peak, and the attenuation from the third peak is
slower than the attenuation from the second peak. As described above, the reason why the
attenuation gradually decreases is considered to be that the energy of the loud sound output at
the previous time is sufficiently remaining in the loud sound space 40 until the next loud sound
is output. In such a case, it is considered that the specific frequency (300 Hz) of the measurement
signal is likely to be the resonance frequency of the loud space 40.
[0130]
The resonance frequency of the loud sound space 40 can be detected by determining the state of
the sound pressure level attenuation process of the loud sound space 40 while gradually
changing the specific frequency of the measurement signal by the measurement / control unit
08-05-2019
36
115 . As one mode of gradually changing the specific frequency of the measurement signal, for
example, a mode may be adopted in which the specific frequency is gradually raised by 1/48
octave.
[0131]
FIG. 20 is a schematic block diagram of a system and a detection device (resonance frequency
detection device) for detecting a resonance frequency in a loudspeaker space (for example, a
concert hall or a gymnasium) 40.
[0132]
Similarly to the system Sg of FIG. 15, the system Sh of FIG. 20 also includes a transmitter 111
which is a sound source means for emitting a measurement signal, an amplifier 12, and a speaker
13 which receives and amplifies an output signal of the amplifier 12 and a speaker A microphone
14 for receiving a loud sound emitted by the radio receiver 13 and a measurement / control unit
115 for inputting an output signal of the microphone 14 are provided.
The measurement / control unit 115 can control the frequency of the measurement signal output
from the transmitter 111 and the time interval of the measurement signal. The measurement /
control unit 115 also functions as a measurement unit that measures the attenuation
characteristic of the output signal of the microphone 14.
[0133]
The detection device 500 includes a transmitter 111, a measurement / control unit 115, and a
mixing device 116.
[0134]
The system Sh of FIG. 20 is different from the system Sg of FIG. 15 in that in the system Sh of
FIG. 20, the measurement signal from the transmitter 111 and the output signal of the
microphone 14 are mixed (combined) by the mixing device 116, This synthesized signal is sent to
the amplifier 12.
08-05-2019
37
The mixing device 116 functions as a signal output unit. As described above, when such a
feedback loop is provided, the resonance of the loud sound space 40 is more emphasized and
measured.
[0135]
Also with the system Sh of FIG. 20, the resonance frequency of the loud sound space 40 can be
detected as in the system Sg of FIG. Moreover, the resonance frequency can be detected more
clearly than when the system Sg of FIG. 15 is used.
[0136]
FIG. 21 is a schematic block diagram of a system and a detection device (resonance frequency
detection device) for detecting a resonance frequency in a loud sound space (for example, a
concert hall or a gymnasium) 40, and FIG. The device 601 is shown, and FIG. 21 (b) shows the
system Si2 and the detection device 602.
[0137]
Similarly to the system Sg of FIG. 15, the systems Si1 and Si2 of FIG. 21 also have a transmitter
111 which is a sound source means for emitting a measurement signal, an amplifier 12, and a
speaker 13 which receives and amplifies the output signal of the amplifier 12. , A microphone 14
for receiving a loud sound emitted by the speaker 13, and a measurement / control unit 115 for
inputting an output signal of the microphone 14.
The measurement / control unit 115 can control the frequency of the measurement signal output
from the transmitter 111 and the time interval of the measurement signal. The measurement /
control unit 115 also functions as a measurement unit that measures the attenuation
characteristic of the output signal of the microphone 14.
[0138]
In the system Si1 of FIG. 21A, the detection device 601 is configured of a transmitter 111, a
measurement / control unit 115, a mixing unit 116, and a delay device 128. The measurement
08-05-2019
38
signal from the transmitter 111 and the output signal of the microphone 14 input by the
detection device 601 are synthesized by the mixing unit 116, and the synthesized signal is
output from the detection device 601 via the delay device 128. The output signal of the detection
device 601 is sent to the amplifier 12. Also, the output signal of the microphone 14 input by the
detection device 601 is branched and sent out to the measurement / control unit 115 and the
mixing unit 116.
[0139]
In the system Si2 of FIG. 21B, the detection device 602 is configured of a transmitter 111, a
measurement / control unit 115, a mixing unit 116, and a delay device 128. The measurement
signal from the transmitter 111 and the output signal of the delay device 128 are combined by
the mixing unit 116, and the combined signal is output from the detection device 601. The
output signal of the microphone 14 input by the detection device 601 is branched and sent out
to the delay device 128 and the measurement / control unit 115.
[0140]
21 differs from the system Sg of FIG. 15 in that in the systems Si1 and Si2 of FIG. 21, the signal
for measurement from the transmitter 111 is amplified from the speaker 13 and the delay device
128 is This is the point at which the output signal of the microphone 14 that has passed is
amplified. As described above, when such a feedback loop is provided, the resonance of the loud
sound space 40 is more emphasized and measured. In the detection devices 601 and 602 of the
systems Si1 and Si2, the mixing unit 116 and the delay device 128 constitute a signal output
unit.
[0141]
The delay device 128 is controlled by the measurement / control unit 115. That is, the
measurement / control unit 115 can arbitrarily set the delay time of the delay device 128 within
a predetermined time range. For example, the delay device 128 can set the delay time of the
delay device 128 to 0 msec, can also set it to 1 msec, and can also set it to 2 msec.
[0142]
08-05-2019
39
Also in this measurement by the systems Si1 and Si2, for example, a sine wave of 250 Hz which
is a specific frequency is continuously output for 0.1 seconds from the oscillator 111, and
thereafter 0.1 seconds is again set at a time interval of 0.9 seconds. The output may be continued
for a second, and the output may be continued for 0.1 second at a time interval of 0.9 seconds.
That is, a 250 Hz sine wave that lasts for 0.1 seconds three times intermittently at one second
intervals is output.
[0143]
FIG. 22 is a diagram showing the sound pressure level measured by the microphone 14 on the
time axis when the measurement signal as described above is output from the oscillator 111 of
the detection device 601, 602. As shown in FIG. However, at this time, the delay time of the delay
device 128 is set to 0 ms.
[0144]
As understood from FIG. 22, in the sound pressure level curve, three peak points occur at one
second intervals so as to be synchronized with the measurement signal. The sound pressure level
decays slowly. As described above, when the sound pressure level decays slowly in the loud
space, it is considered that the specific frequency (250 Hz) of the measurement signal may be the
resonance frequency of the loud space 40. However, this particular frequency (250 Hz) may not
be the resonant frequency but the feedback frequency. Even if the specific frequency (250 Hz) is
the feedback frequency, the sound pressure level decays slowly.
[0145]
Therefore, in order to determine whether this specific frequency (250 Hz) is the resonance
frequency or the feedback frequency, the same measurement is performed while changing the
delay time of the delay device 128. The oscillator 111 intermittently outputs a 250 Hz sine wave
lasting for 0.1 seconds three times, but when measuring the sound pressure level of the loud
sound space 40 in synchronization with the first output, the delay of the delay device 128 is For
example, when setting the time to 0 ms and synchronizing with the second output to measure the
sound pressure level of the sound expansion space 40, set the delay time of the delay unit 128 to
08-05-2019
40
1 ms, for example, and synchronize with the third output. When measuring the sound pressure
level of the loud sound space 40, the delay time of the delay device 128 is set to 2 msec, for
example.
[0146]
Since the resonance frequency is determined only by the characteristics of the loud sound space
40, it does not change even if the configuration of the feedback loop changes. If the specific
frequency (250 Hz) is a resonance frequency, even if the delay time of the delay device 128 is
changed, the speed of attenuation of the sound pressure level measured in the sounding space
40 does not change.
[0147]
However, the feedback frequency changes as the configuration of the feedback loop changes.
Changing the delay time of the delay device 128 changes the configuration of the feedback loop.
Therefore, if the specific frequency (250 Hz) is a feedback frequency when the delay time of the
delay device 128 is set to 0 ms, the sound pressure measured in the loud sound space 40 when
the delay time of the delay device 128 is changed The rate of decay of the level also changes.
[0148]
FIG. 23 shows the sound pressure level measured by the microphone 14 on the time axis when
the above measurement signal is output from the oscillator 111 while changing the delay time of
the delay device 128 as described above. FIG. Strictly speaking, although the sound pressure
level curve measured by the system Si1 of FIG. 21 (a) and the sound pressure level curve
measured by the system Si2 of FIG. 21 (b) are not identical, Explain without.
[0149]
As understood from FIG. 23, in the sound pressure level curve, three peak points occur at one
second intervals so as to be synchronized with the measurement signal. The sound pressure level
of the loud sound space 40 corresponding to the first output from the oscillator 111 is gently
08-05-2019
41
attenuated. The sound pressure level of the loud sound space 40 corresponding to the second
output attenuates relatively quickly. The sound pressure level of the loud sound space 40
corresponding to the third output attenuates somewhat slowly.
[0150]
Thus, by changing the delay time of the delay device 128, the speed of attenuation of the sound
pressure level of the sound expansion space 40 is changed, so the specific frequency (250 Hz) of
the measurement signal is not the resonance frequency It can be judged.
[0151]
The resonance frequency of the loud sound space 40 is fed back by judging the state of the
sound pressure level attenuation process of the loud sound space 40 as described above while
gradually changing the specific frequency of the measurement signal by the measurement /
control unit 115 It can be detected separately from the frequency.
[0152]
FIG. 24 is a schematic block diagram of a system and a detection device (resonance frequency
detection device) for detecting a resonance frequency in a sound expansion space (for example, a
concert hall or a gymnasium) 40, and FIG. The detection device 701 is shown, and the system Sj
2 and the detection device 702 are shown in FIG.
[0153]
Similarly to the system Sg of FIG. 15, the systems Sj1 and Sj2 of FIG. 24 also include a transmitter
111 which is a sound source means for emitting a measurement signal, an amplifier 12, and a
speaker 13 which receives and amplifies an output signal of the amplifier 12. , A microphone 14
for receiving a loud sound emitted by the speaker 13, and a measurement / control unit 115 for
inputting an output signal of the microphone 14.
The measurement / control unit 115 can control the frequency of the measurement signal output
from the transmitter 111 and the time interval of the measurement signal.
The measurement / control unit 115 also functions as a measurement unit that measures the
attenuation characteristic of the output signal of the microphone 14.
08-05-2019
42
[0154]
The detection device 701 of FIG. 24A includes a transmitter 111 as a sound source means, a
measurement / control unit 115, a mixing unit 116, a changeover switch 131, and a phase
inversion device 132.
In the detection device 701, the output signal of the microphone 14 is branched to the
measurement / control unit 115 and the mixing unit 116 and sent out. The measurement signal
from the transmitter 111 is also input to the mixing unit 116. The mixing unit 116 combines the
output signal of the microphone 14 and the measurement signal from the transmitter 111, and
this combined signal is branched into the phase inverting device 132 and the changeover switch
131 and sent out. The output signal of the phase inverter 132 is also sent to the changeover
switch 131. Then, the signal from the changeover switch 131 is sent to the amplifier 12.
[0155]
The detection device 702 in FIG. 24B includes a transmitter 111 as a sound source means, a
measurement / control unit 115, a mixing unit 116, a changeover switch 131, and a phase
inversion device 132. In the detection device 702, the output signal of the microphone 14 is
branched into the measurement / control unit 115, the phase inversion device 132, and the
changeover switch 131 and sent out. The output signal of the phase inverter 132 is sent to the
changeover switch 131. The output signal of the changeover switch 31 is sent to the mixing unit
116. The measurement signal from the transmitter 111 is also input to the mixing unit 116. The
mixing unit 116 combines the measurement signal from the transmitter 111 and the signal from
the changeover switch 131, and sends this combined signal to the amplifier 12.
[0156]
In the systems Sj1 and Sj2, the measurement signal is amplified from the speaker 13. Further,
from the speaker 13, the output signal of the microphone 14 or the phase inversion signal
obtained by inverting the phase of the output signal of the microphone 14 is amplified. In the
detection devices 701 and 702 of the systems Sj 1 and Sj 2, signal output means are configured
by the mixing unit 116, the changeover switch 131, and the phase inversion device 132.
08-05-2019
43
[0157]
It is possible to select whether the output signal of the microphone 14 is to be amplified from the
speaker 13 without phase inversion or to be amplified after phase inversion by switching the
changeover switch 131. The changeover switch 131 is controlled by the measurement / control
unit 115. Therefore, the measurement / control unit 115 can select whether the output signal of
the microphone 14 is to be amplified without phase inversion or to be amplified after phase
inversion from the speaker 13.
[0158]
Although the systems Sj1 and Sj2 also include feedback loops, as described above, the
resonances of the loud sound space 40 are more emphasized and measured when such feedback
loops are provided.
[0159]
When the switch 131 is set so that the speaker 13 amplifies the output signal of the microphone
14 without phase inversion, and the switch 131 is set so that the output signal of the microphone
14 is phase inverted and then the speaker 13 amplifies the signal. The configuration of the
feedback loop is different from when it was done.
[0160]
Also in the measurement by the systems Sj1 and Sj2, for example, a sine wave of 250 Hz which is
a specific frequency is continuously output for 0.1 seconds from the oscillator 111, and
thereafter 0.1 seconds is again set at a time interval of 0.9 seconds. The output may be continued
for a second, and the output may be continued for 0.1 second at a time interval of 0.9 seconds.
That is, a 250 Hz sine wave that lasts for 0.1 seconds three times intermittently at one second
intervals is output.
[0161]
08-05-2019
44
FIG. 25 is a diagram showing the sound pressure level measured by the microphone 14 on the
time axis when the above measurement signals are output from the oscillator 111 in the systems
Sj1 and Sj2.
However, at this time, the state of the changeover switch 131 is set so that the speaker 13 can
increase the sound of the output signal of the microphone 14 without inverting the phase.
[0162]
As understood from FIG. 25, in the sound pressure level curve, three peak points occur at one
second intervals so as to be synchronized with the measurement signal. The sound pressure level
decays slowly.
[0163]
As described above, when the sound pressure level decays slowly in the loud sound space, it is
considered that the specific frequency (250 Hz) of the measurement signal may be the resonance
frequency of the loud sound space 40. (250 Hz) may not be the resonant frequency but the
feedback frequency. Even if the specific frequency (250 Hz) is the feedback frequency, the sound
pressure level decays slowly.
[0164]
Therefore, in order to determine whether this specific frequency (250 Hz) is the resonance
frequency or the feedback frequency, the same measurement is performed while switching the
changeover switch 131. The oscillator 111 intermittently outputs a 250 Hz sine wave that lasts
for 0.1 seconds three times. For example, when measuring the sound pressure level of the loud
sound space 40 in synchronization with the first output, the microphone 14 When the switch
131 is set to a state in which the speaker 13 can perform loudening without inverting the phase
of the output signal and the sound pressure level of the loud sound space 40 is measured in
synchronization with the second output, When setting the switch 131 so that the output signal
can be phase-inverted by the phase inverter 132 and then amplified by the speaker 13 and
measuring the sound pressure level of the loud-sound space 40 in synchronization with the third
08-05-2019
45
output, The switch 131 is set in a state where the output signal of the microphone 14 can be
amplified by the speaker 13 without inverting the phase.
[0165]
As described above, the resonance frequency is determined only by the characteristics of the
sounding space 40, and does not change even if the configuration of the feedback loop changes.
If the specific frequency (250 Hz) is a resonance frequency, the speed of attenuation of the sound
pressure level of the sound expansion space 40 does not change even if the configuration of the
feedback loop changes.
[0166]
However, as described above, the feedback frequency changes due to the change in the
configuration of the feedback loop. The feedback loop that does not cause phase inversion of the
output signal of the microphone 14 and the feedback loop that causes phase inversion of the
output signal of the microphone 14 are different in configuration. Therefore, if the specific
frequency (250 Hz) is a feedback frequency caused by a feedback loop that does not cause phase
inversion of the output signal of the microphone 14, the configuration of the feedback loop is
such that the phase of the output signal of the microphone 14 is inverted. When it changes, the
speed of attenuation of the sound pressure level of the loud sound space 40 also changes.
[0167]
FIG. 26 shows the sound pressure level measured by the microphone 14 on the time axis when
the above measurement signal is output from the oscillator 111 while switching the changeover
switch 131 in the systems Sj1 and Sj2. FIG. Strictly speaking, although the sound pressure level
curve measured by the system Sj1 of FIG. 24 (a) and the sound pressure level curve measured by
the system Sj2 of FIG. 24 (b) are not identical, Explain without.
[0168]
As understood from FIG. 26, in the sound pressure level curve, three peak points occur at one
08-05-2019
46
second intervals so as to be synchronized with the measurement signal. When the sound
pressure level of the loud sound space 40 is measured in synchronization with the first output
from the oscillator 111, the sound pressure level is gradually attenuated. When the sound
pressure level of the loud sound space 40 is measured in synchronization with the second output,
the sound pressure level is rapidly attenuated. When the sound pressure level of the loud sound
space 40 is measured in synchronization with the third output, the sound pressure level is gently
attenuated.
[0169]
As described above, the speed of attenuation of the sound pressure level of the sound expansion
space 40 changes depending on whether the output signal of the microphone 14 is phaseinverted and amplified by the speaker 13 or by the speaker 13 without phase inversion.
Therefore, it can be determined that the specific frequency (250 Hz) of the measurement signal
is not the resonance frequency.
[0170]
The resonance frequency of the loud sound space 40 is fed back by judging the state of the
sound pressure level attenuation process of the loud sound space 40 as described above while
gradually changing the specific frequency of the measurement signal by the measurement /
control unit 115 It can be detected separately from the frequency.
[0171]
In the above, various apparatuses and methods for detecting the resonance frequency in the loud
space 40 have been described with reference to FIGS.
[0172]
Next, a method of selecting a frequency to be set as the dip center frequency in the dip filter 4
(see FIG. 1) from among the resonance frequencies detected in this manner will be described.
[0173]
It has been described above that measurement using the system Sa of FIG. 2 and the system Sb of
FIG. 3 can obtain frequency characteristics as shown in FIG. 4 and frequency characteristics as
shown in FIG.
08-05-2019
47
Furthermore, it has been described that the frequency f1, the frequency f21 and the frequency f3
which are peaks showing peaks in the positive direction in the characteristic curve Db of FIG. 5
are likely to be resonance frequencies or feedback frequencies.
[0174]
In the following, in order to simplify the explanation, dip filter 4 (see FIG. 1) is set as the dip
center frequency on the premise that all of these frequencies (frequency f1, frequency f21 and
frequency f3) are resonance frequencies. Describe how to select the frequency to be used.
[0175]
First, a predetermined number of frequencies from among the frequency f1, the frequency f21
and the frequency f3 are selected as candidates for the dip center frequency to be set as the
removal frequency in the dip filter 4.
Specifically, among these frequencies, candidate frequencies are selected in order from the one
with the largest amplitude level of the curve Cb in FIG.
[0176]
FIG. 27 is a characteristic diagram in which only the curve Cb is extracted from FIG.
In FIG. 27, the vertical axis and the horizontal axis are both logarithmic axes, and the vertical axis
indicates the amplitude level and the horizontal axis indicates the frequency.
In the curve Cb of FIG. 27, the amplitude level at the frequency f21 is the largest, the amplitude
level at the f3 is the second largest, and the amplitude level at the f1 is the second largest.
Here, if the number of frequencies to be selected as candidates is “3”, all of the frequency f1,
the frequency f21, and the frequency f3 become candidate frequencies. If the number of
frequencies to be selected as a candidate is "2", frequencies f21 and f3 become candidate
08-05-2019
48
frequencies.
[0177]
Then, the center frequency of the dip to be set in the dip filter 4 may be determined by the
priority based on the magnitude of the amplitude level of the curve Cb in FIG. Therefore, if the
number of dips to be set in the dip filter 4 of FIG. 1 is, for example, “2”, the frequency f21 and
the frequency f3 are set as the center frequency of the dip of the dip filter 4. Further, for
example, if the number of dips to be set in the dip filter 4 of FIG. 1 is “1”, only the frequency
f21 is set as the center frequency of the dip of the dip filter 4.
[0178]
Thus, the center frequency of the dip to be set in the dip filter 4 may be finally determined by the
priority based on the magnitude of the amplitude level of the curve Cb of FIG. 27. However, the
amplitude of the curve Cb of FIG. After selecting the center frequencies of the dips to be set in
the dip filter 4 according to the priority based on the level size, the candidate (dip filter) is
further selected based on the magnitude of the amplitude level in the curve Db of FIG. The
candidate of the dip center frequency to be set may be reordered.
[0179]
Now, it is assumed that all of the frequency f1, the frequency f21, and the frequency f3 become
candidate frequencies by the selection based on the magnitude of the amplitude level of the
curve Cb in FIG.
Next, the candidates are reordered in these candidate frequencies (frequency f1, f21, f3). The
order is such that the amplitude level in the amplitude frequency characteristic curve Db of FIG.
Among the frequencies f1, f21 and f3, the frequency f3 has the largest amplitude level in the
curve Db of FIG. 5, the frequency f21 has the second largest amplitude level, and the second has
the next largest amplitude level. The frequency is f1. Therefore, the frequency f3 is the first
candidate frequency, the frequency f21 is the second candidate frequency, and the frequency f1
is the third candidate frequency.
[0180]
08-05-2019
49
If the number of dips to be set in the dip filter 4 of FIG. 1 is, for example, “2”, the frequency f3
and the frequency f21 are set as the center frequency of the dip of the dip filter 4. For example,
when the number of dips to be set in the dip filter 4 of FIG. 1 is “1”, only the frequency f3 is
set as the dip center frequency of the dip filter 4.
[0181]
In this way, it is possible to objectively select the dip center frequency to be set in the dip filter 4
without the need for experience or skill. By doing so, it is possible to effectively prevent the
resonance in the loudspeaker space 40 of FIG.
[0182]
It should be noted that after selecting candidates for center frequencies of a plurality of dips to
be set in dip filter 4 according to the priority based on the magnitude of the amplitude level of
curve Cb in FIG. The reason for reordering the candidates (candidates of dip center frequencies
to be set for the dip filter) based on the following reasons is as follows. That is, the curve Cb in
FIG. 27 includes not only the characteristic due to the resonance of the loud sound space 40 but
also the amplitude frequency characteristic of the electroacoustic system (system consisting of
the amplifier 12, the speaker 13, the microphone 14 and the like). In addition to the
characteristics of resonance, the characteristics are largely dependent on the amplitude
frequency characteristics of the electroacoustic system. On the other hand, in the curve Db of
FIG. 5, the characteristic due to the resonance of the loud space 40 appears remarkably, and the
influence of the amplitude frequency characteristic of the electroacoustic system is small.
Therefore, it is more effective for preventing the resonance of the loud sound space 40 to finally
determine the dip center frequency to be set to the dip filter 4 based on the magnitude of the
amplitude level in the curve Db of FIG. is there.
[0183]
The above-described resonance frequency selection method is also effective when the number of
dips to be set in the dip filter and the number of detected resonance frequencies are larger. For
example, when there are 200 or more detected resonance frequencies, frequencies from the
08-05-2019
50
largest amplitude level to 120 frequencies may be left as candidates in the curve Cb of FIG. 27
and the remaining frequencies may be excluded from the candidates. Further, the candidates are
reordered based on the magnitude of the amplitude level in the curve Db of FIG. 5 with respect to
the 120 frequencies, and the upper eight frequencies in the reassigned order are dip filters to the
dip center frequency It may be set as
[0184]
The embodiment of the present invention has been described above based on FIGS.
[0185]
In the above embodiment, the resonance frequency detection method and the device of the
present invention are applied to the detection of the resonance frequency in the loud space
where the acoustic equipment is disposed, but the resonance frequency detection method and
the device of the present invention are the The present invention can be applied not only to such
a loud sound space but also to any space (sound loud space) where resonance frequency
detection is required.
For example, in order to know the liquid filling amount in the liquid tank, the volume of the space
not filled with the liquid in the tank can also be applied to a technique of measuring the
resonance frequency.
[0186]
According to the present invention, the resonance frequency can be accurately detected without
the need for experience or skill, and the frequency to be set as the dip center frequency in the dip
filter can be appropriately selected. Therefore, it is useful, for example, in the technical field of
electroacoustics.
[0187]
It is a schematic block diagram of an acoustic system installed in a loud-speaking space (for
example, a concert hall or a gymnasium). FIG. 1 is a schematic block diagram of a system for
08-05-2019
51
measuring amplitude frequency characteristics in a loudspeaker space (eg, a concert hall or
gymnasium). FIG. 1 is a schematic block diagram of a system for measuring amplitude frequency
characteristics in a loudspeaker space. It is a characteristic view which shows typically the
amplitude frequency characteristic of loud sound space measured by the system of FIG. 2, and
the amplitude frequency characteristic of loud sound space measured by the system of FIG. It is
the frequency characteristic figure which deducted the characteristic of real curve Ca from the
characteristic of broken curve Cb of FIG. FIG. 1 is a schematic block diagram of a system for
measuring amplitude frequency characteristics in a loudspeaker space. It is a characteristic view
which shows typically the amplitude frequency characteristic of the loud sound space measured
by the system of FIG. 2, and the amplitude frequency characteristic of the loud sound space
measured by the system of FIG. It is a frequency characteristic figure which deducted the
characteristic of real curve Ca from the characteristic of broken curve Cc of FIG. FIG. 1 is a
schematic block diagram of a system including a detection apparatus which is an embodiment of
a resonance frequency detection apparatus according to the present invention. It is a figure
which shows the example of the structure which can be employ | adopted as a delay apparatus in
the detection apparatus of FIG. FIG. 1 is a schematic block diagram of a system for measuring
amplitude frequency characteristics in a loudspeaker space. It is a characteristic view which
shows typically the amplitude frequency characteristic of the loud sound space measured by the
system of FIG. 2, and the amplitude frequency characteristic of the loud sound space measured
by the system of FIG. It is the frequency characteristic figure which deducted the characteristic of
real curve Ca from the characteristic of broken curve Ce of FIG. FIG. 1 is a schematic block
diagram of a system including a detection apparatus which is an embodiment of a resonance
frequency detection apparatus according to the present invention. FIG. 1 is a schematic block
diagram of a system for detecting resonant frequencies in a loudspeaker space (eg, a concert hall
or gymnasium). It is a figure which represented the signal level of the signal for measurement on
the time-axis. It is the figure which represented the sound pressure level measured with the
microphone on the time-axis. It is the figure which represented the sound pressure level
measured with the microphone on the time-axis. It is the figure which represented the sound
pressure level measured with the microphone on the time-axis. FIG. 1 is a schematic block
diagram of a system for detecting resonant frequencies in a loudspeaker space (eg, a concert hall
or gymnasium). FIG. 1 is a schematic block diagram of a system for detecting resonant
frequencies in a loudspeaker space (eg, a concert hall or gymnasium). It is the figure which
represented the sound pressure level measured with the microphone on the time-axis.
It is the figure which represented the sound pressure level measured with the microphone on the
time-axis. FIG. 1 is a schematic block diagram of a system for detecting resonant frequencies in a
loudspeaker space (eg, a concert hall or gymnasium). It is the figure which represented the sound
pressure level measured with the microphone on the time-axis. It is the figure which represented
the sound pressure level measured with the microphone on the time-axis. It is the characteristic
view which took out only the curve Cb from FIG.
08-05-2019
52
Explanation of sign
[0188]
11 Transmitter 12 amplifier 13 speaker 14 microphone 15 measuring device 16 mixing device
17 delay device 19 phase inversion device 21 transmission unit 25 measurement / control unit
26 mixing unit 27 switching unit 28 delay device 31 changeover switch 32 phase inversion
device 40 loud space 111 Device 115 Measurement / control unit 116 Mixing device 128 Delay
device 131 Switch 132 Phase inverter 201, 202, 301, 302, 400, 500, 601, 602, 701, 702
Detection device
08-05-2019
53
Документ
Категория
Без категории
Просмотров
0
Размер файла
73 Кб
Теги
jp2008252932
1/--страниц
Пожаловаться на содержимое документа