close

Вход

Забыли?

вход по аккаунту

?

JP2001359186

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 JP2001359186
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic device and a filter frequency setting method capable of appropriately removing
unnecessary low frequency components from an audio signal in consideration of the impedance
characteristic of a speaker.
[0002]
2. Description of the Related Art With the spread of car audio and the like, users are able to enjoy
their favorite music and the like even in the car. Recently, the performance of an audio system
adopted for car audio has been improved, and in the audio system, super bass reproduction with
a low cutoff frequency f0 as shown in FIG. 5 has become possible.
[0003]
However, small-diameter speakers (speaker systems) are adopted (mounted) in general car audio.
Such small-aperture speakers have limitations in ultra low frequency reproduction due to their
physical size. That is, as shown in FIG. 5, even if the low frequency cutoff frequency f0 can be
reproduced on the audio system side, the low frequency cutoff frequency f1 inferior to that on
the speaker system side (that is, f1) > F0), and it becomes difficult to reproduce the ultra low
range.
08-05-2019
1
[0004]
For this reason, even if a super-bass signal (audio signal) is supplied, the speaker can not actually
emit as a sound, and consumes useless energy which is inefficient. In addition, when an ultrabass signal is supplied to the speaker, the amplitude of the diaphragm becomes large, and at the
time of high volume, "bottoming" (to reach the vibration limit) occurs. At this time, the user may
hear that the sound from the speaker is mixed with the bottoming sound, or the distortion may
sound worse. For example, the sound wave form which should originally be audible to the user as
a sound wave form including a low frequency component as shown in FIG. 6 (a) should be heard
as a sound wave form without a low frequency component as shown in FIG. The accompanying
sound was mixed, and the sense of distortion was worse.
[0005]
It is also possible to remove unnecessary low frequency components by installing a filter (such as
a digital filter) on the audio system side in consideration of such a speaker that is difficult to
reproduce at very low frequency. However, due to the difference in impedance characteristics
and the like among the adopted speakers, the cut-off frequency set in the filter is not fixed.
Therefore, the user is required to set an appropriate cutoff frequency for the filter after
examining the impedance characteristics and the like of the speaker of the user, which is
expected to be very complicated.
[0006]
The present invention has been made in view of the above situation, and provides an acoustic
device and a filter frequency setting method capable of appropriately removing unnecessary low
frequency components from an audio signal in consideration of the impedance characteristic of a
speaker. With the goal.
[0007]
SUMMARY OF THE INVENTION In order to achieve the above object, an audio apparatus
according to a first aspect of the present invention is an audio apparatus provided with a speaker
having a predetermined impedance characteristic, which is a signal emitted by a transmitter. Is
supplied to the speaker via the resistor, and the identifying means for identifying the impedance
characteristic of the speaker according to the voltage change of the resistor caused by
08-05-2019
2
sequentially changing the signal frequency from the transmitter, and the identifying means
According to the impedance characteristic, an acquisition means for acquiring a corresponding
cutoff frequency, and a setting means for setting the cutoff frequency acquired by the acquisition
means to a filter disposed in front of the speaker are characterized.
[0008]
According to the present invention, the specifying means supplies the signal generated by the
transmitter to the speaker through the resistor, and the impedance of the speaker is changed
according to the voltage change of the resistor caused by sequentially changing the signal
frequency from the transmitter. Identify the characteristics.
The acquisition means acquires the corresponding cutoff frequency according to the impedance
characteristic identified by the identification means, for example, with reference to a table or the
like stored in a predetermined storage unit.
The setting means sets the cutoff frequency acquired by the acquisition means in the filter
disposed in front of the speaker. As a result, by setting a cutoff frequency determined in
accordance with the impedance characteristic of the speaker in the filter, unnecessary low
frequency components can be appropriately removed from the audio signal.
[0009]
In order to achieve the above object, an audio apparatus according to a second aspect of the
present invention is an audio apparatus provided with a speaker having a predetermined
impedance characteristic, which comprises: transmitting means for emitting a signal of an
arbitrary frequency; A resistor connected between the speaker and the speaker, measurement
means for measuring a voltage applied to both ends of the resistor when a signal is emitted from
the transmission means toward the speaker, and the transmission means According to the
voltage measured by the measuring means while sequentially changing the frequency of the
signal to be emitted, a specifying means for specifying the impedance characteristic of the
speaker and a corresponding cutoff frequency are obtained according to the impedance
characteristic specified by the specifying means Acquisition means and a cut-off frequency
acquired by the acquisition means are set, and in front of the speaker, the sound source is spear
Characterized in that it comprises a filter that removes a predetermined frequency component
from an audio signal supplied towards.
08-05-2019
3
[0010]
According to the present invention, the transmitting means comprises a signal transmitter etc.
and emits a signal of an arbitrary frequency.
The resistor is, for example, a resistor of negligible resistance with respect to the nominal
impedance of the loudspeaker, and is connected between the transmitting means and the
loudspeaker. The measuring means measures a voltage applied to both ends of the resistor when
a signal is emitted from the transmitting means to the speaker. The specification means specifies
the impedance characteristic of the speaker according to the voltage measured by the
measurement means while sequentially changing the frequency of the signal emitted by the
transmission means. The acquisition means acquires the corresponding cutoff frequency
according to the impedance characteristic identified by the identification means, for example,
with reference to a table or the like stored in a predetermined storage unit. The filter is set with
the cutoff frequency acquired by the acquisition means, and removes a predetermined frequency
component from the audio signal supplied from the predetermined sound source to the speaker
at the front stage of the speaker. As a result, unnecessary low frequency components can be
appropriately removed from the audio signal in consideration of the impedance characteristic of
the speaker.
[0011]
In order to achieve the above object, an audio apparatus according to a third aspect of the
present invention is an audio apparatus provided with a speaker having a predetermined
impedance characteristic, and transmitting means for selecting and emitting a signal of an
arbitrary frequency; A resistor connected between the transmitting means and the speaker; and
measuring means for measuring a voltage difference applied to both ends of the resistor when a
signal is emitted from the transmitting means toward the speaker; The frequency specifying
means for specifying the limit frequency at which the voltage difference measured by the
measuring means becomes the smallest while sequentially changing the frequency of the signal
emitted by the transmitting means, and the correspondence between the plurality of limit
frequencies and the cutoff frequency According to the limit frequency specified by the frequency
specifying means from the memory means for storing in advance the frequency table to be
stored and the frequency table stored in the memory means Selection means for selecting the
cut-off frequency to be selected and the cut-off frequency selected by the selection means, and a
predetermined low frequency component from an audio signal supplied from the predetermined
sound source toward the speaker And a high pass filter for removing
08-05-2019
4
[0012]
According to the present invention, the transmitting means comprises a signal transmitter or the
like, and selects and emits a signal of an arbitrary frequency.
The resistor is, for example, a resistor of negligible resistance with respect to the nominal
impedance of the loudspeaker, and is connected between the transmitting means and the
loudspeaker. The measuring means measures a voltage difference applied to both ends of the
resistor when a signal is emitted from the transmitting means to the speaker. The frequency
specifying means specifies the limit frequency at which the voltage difference measured by the
measuring means is the smallest while sequentially changing the frequency of the signal emitted
by the transmitting means. The storage means prestores a frequency table defining the
correspondence between the plurality of limit frequencies and the cutoff frequency. The selection
means selects a corresponding cutoff frequency from the frequency table stored in the storage
means in accordance with the limit frequency identified by the frequency identification means.
The high-pass filter is set with the cutoff frequency selected by the selection means, and removes
a predetermined low frequency component from the audio signal supplied from the
predetermined sound source toward the speaker at the front stage of the speaker. As a result,
unnecessary low frequency components can be appropriately removed from the audio signal in
consideration of the impedance characteristic of the speaker.
[0013]
In order to achieve the above object, a filter frequency setting method according to a fourth
aspect of the present invention is to supply a signal emitted by a transmitter to a speaker via a
resistor and to sequentially change a signal frequency from the transmitter In the identification
step of identifying the impedance characteristic of the speaker according to the voltage change of
the resistor caused by the acquisition step, the acquisition step of acquiring the corresponding
cutoff frequency according to the impedance characteristic specified in the identification step,
and And a setting step of setting the cut-off frequency to a filter disposed in front of the speaker.
[0014]
According to the present invention, the specifying step supplies the signal emitted by the
transmitter to the speaker through the resistor, and the impedance of the speaker is changed
according to the voltage change of the resistor caused by sequentially changing the signal
08-05-2019
5
frequency from the transmitter. Identify the characteristics.
The acquiring step acquires a corresponding cutoff frequency according to the impedance
characteristic identified in the identifying step, for example, with reference to a table or the like
stored in a predetermined storage unit. In the setting step, the cutoff frequency acquired in the
acquiring step is set in the filter disposed in front of the speaker. As a result, by setting a cutoff
frequency determined in accordance with the impedance characteristic of the speaker in the
filter, unnecessary low frequency components can be appropriately removed from the audio
signal.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION An on-vehicle acoustic apparatus according
to an embodiment of the present invention will be described below with reference to the
drawings.
[0016]
FIG. 1 is a circuit diagram showing an example of the configuration of a vehicle-mounted acoustic
device applied to the embodiment of the present invention.
As shown in FIG. 1, the vehicle-mounted acoustic device includes a sound source 1, a
measurement transmitter 2, switches 3 a to 3 c, switches 4 a to 4 c, a high pass filter 5, a system
amplifier 6, and a measurement resistor 7. , A speaker 8, buffer amplifiers 9a and 9b, a
differential amplifier 10, an integration circuit 11, an A / D converter 12, and a microcomputer
13.
[0017]
The sound source 1 includes, for example, a disc reproducing apparatus for reproducing a music
CD (compact disc), and an audio signal (reproduction signal) obtained by reproducing the target
CD is transmitted to the high pass filter 5 via the switch 3a or the like. Supply.
[0018]
The measuring transmitter 2 is controlled by the microcomputer 13 to emit a signal of an
arbitrary frequency, and supplies the signal to the system amplifier 6 via the switch 4a and the
08-05-2019
6
like.
[0019]
The switches 3a to 3c include relays and the like, and are controlled to be on and off by the
microcomputer 13, respectively.
The switches 3a to 3c are all turned on during normal use when an audio signal is output from
the sound source 1.
[0020]
Similarly, the switches 4a to 4c also include relays and the like, and are ON / OFF controlled by
the microcomputer 13.
The switches 4a to 4c are all turned on when measuring the impedance characteristic of the
speaker 8.
[0021]
The high pass filter 5 is, for example, a digital filter such as a FIR (Finite Impulse Response) filter,
and removes unnecessary low frequency components included in the audio signal supplied from
the sound source 1 according to the set cutoff frequency. The cut-off frequency is set by the
microcomputer 13.
[0022]
The system amplifier 6 amplifies an audio signal or the like from which unnecessary low
frequency components are removed by the high pass filter 5, and supplies the amplified audio
signal or the like to the speaker 8 through the switch 3c.
[0023]
08-05-2019
7
The measuring resistor 7 is a resistor for measuring the impedance of the speaker 8.
Specifically, the measurement resistor 7 is a resistor having a negligible resistance value with
respect to the nominal impedance of the speaker 8 and is inserted in series between the system
amplifier 6 and the speaker 8.
[0024]
The speaker 8 is a speaker system having a predetermined impedance characteristic, and emits a
sound (musical sound or the like) in accordance with an audio signal supplied via the system
amplifier 6.
[0025]
The buffer amplifiers 9a and 9b are amplifiers applied to both ends of the measuring resistor 7
to measure a voltage.
Specifically, the buffer amplifiers 9a and 9b supply the voltages measured at points TP2 and TP3
shown in FIG. 1 to the differential amplifier 10.
[0026]
The differential amplifier 10 measures the voltage generated across the measuring resistor 7 in
accordance with the voltages supplied from the buffer amplifiers 9a and 9b. The differential
amplifier 10 supplies the measured voltage to the integration circuit 11 as an output voltage.
[0027]
The integration circuit 11 converts an AC signal indicating the output voltage supplied from the
differential amplifier 10 into a DC signal. The integration circuit 11 supplies the output voltage
converted into the DC signal to the A / D converter 12.
08-05-2019
8
[0028]
The A / D converter 12 digitizes the output voltage output from the integration circuit 11. That
is, the A / D converter 12 digitizes the voltage applied across the measuring resistor 7 and
supplies it to the microcomputer 13.
[0029]
The microcomputer 13 includes, for example, a read only memory (ROM), a random access
memory (RAM), a central processing unit (CPU), a driver circuit, and the like, and the
measurement transmitter 2, the switches 3a to 3c, and the switch 4a. Through 4c and the high
pass filter 5 etc. Further, the microcomputer 13 obtains the voltage applied to both ends of the
measurement resistor 7 through the A / D converter 12 and the like.
[0030]
Specifically, the microcomputer 13 measures the impedance characteristic of the speaker 8 by
measuring the voltage applied to both ends of the measuring resistor 7 while sequentially
changing the frequency set in the measuring transmitter 2. The voltage (voltage difference)
between both ends of the measurement resistor 7 is expressed by Equation 1.
[0031]
VTP2−VTP3 = R / (R + Zf) · VTP2 VTP2: voltage at TP2 point VTP3: voltage at TP3 point R:
resistance value of resistance 7 for measurement Zf: impedance of speaker 8
[0032]
In the formula 1, when R and VTP2 are fixed, the voltage across the measuring resistor 7 is
inversely proportional to 1 + Zf.
08-05-2019
9
For this reason, in the impedance Zfm at the lowest resonance frequency of the speaker 8, the
voltage across the measuring resistor 7 becomes the smallest. That is, the impedance
characteristic of the speaker 8 can be grasped by specifying the frequency when the voltage
applied to both ends of the measuring resistor 7 is minimum.
[0033]
Using this, the microcomputer 13 specifies the reproduction limit frequency indicating the limit
of the very low frequency reproduction in the speaker 8 from the voltage applied to both ends of
the measuring resistor 7. Then, the microcomputer 13 refers to the filter table as shown in FIG. 2
to select the cutoff frequency corresponding to the identified reproduction limit frequency (f2),
and sets the selected cutoff frequency in the high pass filter 5 . The filter table shown in FIG. 2 is
a table that defines the correspondence between the reproduction limit frequency (f2) and the
cutoff frequency, and is stored in advance in the ROM or the like in the microcomputer 13.
[0034]
Hereinafter, the operation of the in-vehicle acoustic device according to the embodiment of the
present invention will be described with reference to FIG. FIG. 3 is a flowchart for explaining the
filter frequency setting process performed by the microcomputer 13. The filter frequency setting
process shown in FIG. 3 is instructed by the user and started, for example, when the speaker 8 of
the in-vehicle acoustic device is replaced with a new one.
[0035]
まず、マイクロコンピュータ13は、スイッチ3a∼3cをOFFし、また、スイッチ4a∼
4cをONする(ステップS11)。 That is, the microcomputer 13 supplies the signal
generated from the measurement transmitter 2 to the system amplifier 6 through the point TP1
shown in FIG. 1, and the amplified signal is transmitted to the speaker 8 through the
measurement resistor 7. The switches 3a to 3c and the switches 4a to 4c are controlled to be
supplied.
[0036]
08-05-2019
10
The microcomputer 13 sets an initial frequency to the measurement transmitter 2 (step S12).
That is, the microcomputer 13 sets 300 Hz to the transmission frequency f1 emitted by the
measurement transmitter 2.
[0037]
The microcomputer 13 sets the initial value 0 at the reproduction limit frequency f2, sets the
initial value 1 at the voltage VTP2, and sets the value of the voltage VTP2 at the comparison
voltage VR0 (step S13).
[0038]
The microcomputer 13 acquires a voltage VR (voltage difference) applied to both ends of the
measurement resistor 7 (step S14).
That is, the voltage VR (voltage difference) is measured by the differential amplifier 10 from the
voltages VTP2 and VTP3 acquired by the buffer amplifiers 9a and 9b, and the voltage VR is
transmitted to the microcomputer 13 via the A / D converter 12 and the like. Supplied.
[0039]
The microcomputer 13 determines whether the voltage VR generated across the measurement
resistor 7 is smaller than the comparison voltage VR0 (step S15).
[0040]
If the microcomputer 13 determines that the voltage VR is not smaller than the comparison
voltage VR0, the process proceeds to step S17 described later.
On the other hand, when determining that the voltage VR is smaller than the comparison voltage
VR0, the microcomputer 13 sets the voltage VR to the comparison voltage VR0 and sets the
transmission frequency f1 to the reproduction limit frequency f2 (step S16).
08-05-2019
11
[0041]
The microcomputer 13 changes the frequency of the measurement transmitter 2 (step S17). That
is, the microcomputer 13 reduces the transmission frequency f1 to 1/2.
[0042]
The microcomputer 13 determines whether the current transmission frequency f1 is greater than
10 Hz (step S18). That is, the microcomputer 13 determines whether or not the measurement of
the voltage VR has been completed for all types of transmission frequencies f1.
[0043]
If the microcomputer 13 determines that the transmission frequency f1 is higher than 10 Hz, the
process returns to step S14, and the above-described processes of steps S14 to S18 are
repeatedly performed. That is, while the transmission frequency f1 of the measurement
transmitter 2 is higher than 10 Hz, the microcomputer 13 changes the transmission frequency f1
sequentially to 300 Hz, 150 Hz, 75 Hz, 37.5 Hz, and 18.75 Hz while measuring resistance 7 The
voltage VR applied to both ends of the signal is measured to specify the reproduction limit
frequency f2 at which the voltage VR is minimum.
[0044]
On the other hand, when it is determined in step S18 that the transmission frequency f1 is not
larger than 10 Hz, the microcomputer 13 sets the cutoff frequency corresponding to the
reproduction limit frequency f2 obtained by the measurement in the high pass filter 5 (step S19).
). That is, the microcomputer 13 refers to the filter table as shown in FIG. 2 stored in the ROM or
the like, and specifies the cutoff frequency corresponding to the reproduction limit frequency f2.
Then, the specified cutoff frequency is set to the high pass filter 5.
[0045]
08-05-2019
12
マイクロコンピュータ13は、スイッチ3a∼3cをONし、また、スイッチ4a∼4cを
OFFする(ステップS20)。 That is, the microcomputer 13 switches the switches 3a to 3c
and the audio signal generated from the sound source 1 to the system amplifier 6 through the
high pass filter 5 and the amplified audio signal to the speaker 8. The switches 4a to 4c are
controlled.
[0046]
As described above, the impedance characteristic of the speaker 8 is measured by the filter
frequency setting process, and the appropriate cutoff frequency is set to the high pass filter 5.
Thereafter, the audio signal emitted from the sound source 1 is supplied to the high pass filter 5
via the switch 3a and the like. Since an appropriate cutoff frequency is set in the high pass filter
5, signal components in unnecessary bands are removed from the passing audio signal. Then, the
audio signal amplified by the system amplifier 6 is supplied to the speaker 8.
[0047]
As a result, it is possible to appropriately improve the mixed modulation that occurs according to
the impedance characteristic of the speaker 8. In addition, since the signal component of the
unnecessary band is removed, the occurrence probability of the bottoming sound can be
appropriately reduced by the speaker 8, so that the reliability (stable sound output) can be
obtained even at a large volume etc. It can be improved. Furthermore, unnecessary signal
components that can not be actually emitted as sound by the speaker 8 are removed, so that it is
possible to suppress wasting energy that is inefficient.
[0048]
In the above embodiment, the circuit (measurement circuit) for measuring the impedance
characteristic of the speaker 8 is included in the circuit (reproduction circuit) for reproducing the
audio signal from the sound source 1 under normal conditions and one circuit Although the
configuration is adopted, the measurement circuit may be separated from the regeneration
circuit.
[0049]
08-05-2019
13
For example, as shown in FIG. 4, the measurement circuit 20 may be separated, and the cutoff
frequency selected by the microcomputer 13 may be set in the high pass filter 5 by remote
control.
In this case, the arrangement of the switches 3a to 3c and the switches 4a to 4 as shown in FIG. 1
is unnecessary, and the control thereof is also unnecessary.
[0050]
Although the above embodiment shows an example in which only the very low frequency is used,
the present invention is not limited to the very low frequency and may be performed for the
entire reproduction frequency. For example, in addition of a tune-up speaker (so-called tweeter),
the low frequency cutoff frequency of the tune-up speaker may be specified and set as a filter.
Further, in the plurality of loudspeakers, identification of the reproduction frequency of the
woofer (cutoff frequency), identification of the reproduction frequency of the squawker, and
identification of the reproduction frequency of the tweeter may be performed. In this case, not
only the low pass high pass filter but also a high pass low pass filter may be provided.
[0051]
In the above embodiment, the frequency of the measurement transmitter 2 is changed at a single
frequency, and the impedance characteristic is specified for the speaker 8. However, the
impedance characteristic is specified using noise instead of the single frequency. It is also good.
In this case, the impedance characteristic of the speaker 8 can be identified by using FFT (Fast
Fourier Transform) analysis when measuring the voltage across the measurement resistor 7.
[0052]
Further, as a method of setting the cutoff frequency to the high pass filter 5, the order of the
filter may be increased or decreased, or a circuit configuration may be adopted to change Q
(quality factor).
[0053]
Moreover, although said embodiment demonstrated the vehicle-mounted acoustic apparatus, it
can apply to a normal audio product (audio system) other than this.
08-05-2019
14
[0054]
As described above, unnecessary low frequency components can be appropriately removed from
the audio signal in consideration of the impedance characteristics of the speaker.
08-05-2019
15
Документ
Категория
Без категории
Просмотров
0
Размер файла
25 Кб
Теги
jp2001359186
1/--страниц
Пожаловаться на содержимое документа