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JPH09327086

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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
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DESCRIPTION JPH09327086
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of correcting a sound field of a speaker, a speaker system, and an acoustic system.
[0002]
2. Description of the Related Art A so-called recording operation is performed by reproducing
original sound played by a player by a monitor speaker and mixing and recording while listening
to the reproduced sound in a control room.
[0003]
Generally, in the field of such recording work, it is ideal that the monitor speaker not only
reproduces the original sound as faithfully as possible, but also that it is not affected by the
reflected sound in the indoor space at all even when listening to the reproduced sound. In
addition to the characteristics of the monitor speaker, the acoustic characteristics in the control
room are also considered to be extremely important factors.
[0004]
For this reason, a designer or a sound contractor is designed by utilizing room acoustic
technology in which reflectors and sound absorbing materials are arranged in a well-balanced
manner so that sound can be attenuated smoothly regardless of frequency at any position in the
control room. In the past, various devices have been widely used to make the sound reproduced
indoors as close as possible to an ideal sound.
08-05-2019
1
[0005]
However, the recording operation in which all the effects of the reflected sound have been
eliminated is impossible in a real studio space, and for this reason, headphones are used, for
example, as in the recording of classical music. Monitoring may be conducted.
Although such monitoring is preferable in that it is not affected by the reflected sound in the
control room or the ambient noise, it grasps important characteristics of the room acoustics such
as the realism, three-dimensional feeling or direction of the sound field. There is a serious
drawback of being difficult to do.
[0006]
In addition, since the room structure of the recording studio varies from place to place, in the
case of monitoring by speakers, although the same original sound is being reproduced, different
sound fields are formed for each place, and There is a drawback that each time mixing work has
to be carried out.
[0007]
Therefore, in view of such problems, the inventor has particularly improved the former among
the two factors that affect the quality of the recording content, that is, the characteristics of the
sound reproduced by the speaker and the acoustic characteristics in the control room. Based on a
certain sound receiving point, the sound output from the speakers is picked up as being close to
the original sound, and how to form a sound field in which the influence of the reflected sound in
the room is removed The present invention has been completed as a result of earnest studies on
the point that it should be done.
[0008]
[Means for Solving the Problems] First, the inventor of the present invention measures that
various characteristics such as frequency characteristics and directivity characteristics of a
speaker are measured at a point 1 m on the axis of the speaker, and the necessary correction is
applied thereon Focusing on the method of sound field correction of the speaker, we examined
the improvement.
08-05-2019
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[0009]
In general, among the various characteristics of the speaker, frequency characteristics and
directivity characteristics are particularly important.
The sound field correction of the speaker is, as shown in FIG. 18, collected by the microphone
103 installed at a point 1 m away from the axis of the measured speaker 101 in the anechoic
chamber, and is based on the measurement result. The sound pressure level of the measured
sound is to be within about ± 4 dB over substantially the entire audio frequency band.
[0010]
By the way, a space in a range where the distance from the speaker unit is smaller than the
aperture of the woofer is generally called a near sound field.
In this near sound field, it can be regarded as a free sound field without the inverse relationship
(inverse square law) between the sound pressure of the sound output from the speaker and the
square of the distance from the cabinet being established. As shown, there is a phenomenon that
a rise occurs in the sound pressure level of the low band (about 80 Hz to about 400 Hz) output
from the woofer.
[0011]
Since the conventional speaker is based on the measurement result at a point 1 m apart on the
axis, it is manufactured in a state where the phenomenon specific to the near sound field, that is,
the sound pressure level rise in the low range immediately after the output is not reflected.
For this reason, when the sound is actually reproduced, the sound of the uplifting sound
reproduces the entire sound without masking (a dull sound) and the difference between the
reproduced sound and the original sound is large. The present inventors focused attention on the
actual state of occurrence.
08-05-2019
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[0012]
Then, based on the measurement method of the various characteristics of such a speaker, as a
result obtained by various experiments in order to solve the above-mentioned subject, the
present inventor has determined the sound pressure level of the sound collected immediately
before the speaker. Adjustment by the first correction means to be within about ± 4 dB over
substantially the entire audio frequency band, and the sound pressure level of the sound
collected at the desired sound receiving point substantially over the entire audio frequency band
And the step of adjusting with the second correction means so as to be within about ± 4 dB.
[0013]
The term “immediately before” means within the range of the so-called near sound field of the
speaker to be measured.
The first and second correction means mean means for changing a frequency characteristic of an
electric signal obtained by converting collected sound to obtain a desired signal, and specifically,
an equalizer is used be able to.
[0014]
This sound field correction method can perform correction for performing sound pressure level
adjustment on the sound immediately after the output of the speaker.
Therefore, according to the sound field correction method consisting of these two steps, the first
correction means can perform sound field correction based on the characteristics reflecting the
influence of the increase in the sound pressure level in the low frequency range. You can get very
close sound.
In addition, since the first correction means can perform correction immediately before and the
second correction means can perform correction at a point 1 m apart from the axis of the
speaker, the law of inverse square can be established from 1 m point can do. Also, if the second
correction means is moved to a desired point after 1 m (for example, a point at 2 m on the axis)
to perform correction, the inverse square law is established in the space after that point. Can.
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[0015]
Moreover, by adjusting the change in the frequency characteristic of the sound generated when
transferred to the desired sound receiving point by the second correction means, the sound
pressure level of the collected sound is approximately ± about the entire audio frequency band.
Since it can be made to be within 4 dB, it becomes possible to pick up a sound very close to the
original sound from which the influence of the reflected sound has been removed at any sound
receiving point.
[0016]
By using the method of the present invention, it is possible to reproduce and listen as the same
sound in any room (in the room to which the present invention is applied) in the room of any
structure.
Therefore, it is possible to solve the problem that when the room changes, the sound changes
and the mixing method changes.
[0017]
The sound field correction method of the present invention is not limited to the sound field
correction in the control room of the recording studio, and it is needless to say that it can be
applied to the sound field correction outdoors, in concert halls, indoors such as theaters and
cinemas. Absent.
[0018]
In this case, in general, in the case of an indoor space such as a concert hall or a theater, a large
space is usually interposed between the speaker and the sound receiving point.
For this reason, the sound field at the sound receiving point has the property that the influence
of the reflected sound is taken into consideration, and the direct sound from the speaker is
largely influenced by the reverberation.
08-05-2019
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[0019]
In general, the influence of reverberation is often manifested in so-called reverberation,
reverberation time, and sense of direction, which are considered to be important factors that
influence the acoustic effect in a room, and this kind of element has more room shape than the
speaker's characteristics. And, it is said that the place by the sound absorbing material is large.
According to the sound field correction method of the present invention, when the sound very
close to the original sound is picked up at the desired sound receiving point, it can be
appropriately adjusted by the second correction means. By correcting the attenuation of the
sound, the direct sound from the speaker can be heard in the reverberation.
[0020]
The present invention is also characterized by a speaker system including correction means for
containing the sound pressure level of the sound collected immediately before the speaker within
about ± 4 dB over substantially the entire audio frequency band.
[0021]
In this speaker system, the sound pressure level adjustment performed on the sound collected
immediately before is performed by itself, and a simple sound that is faithful to the original
sound reflecting or added to the rise of the sound pressure level in the low range is simply
performed. Can.
At this time, it is preferable that the speaker system be provided with a sound collecting means
for collecting the sound output from the unit immediately before, and it is more preferable that
the speaker system be provided with a sound collecting means for each unit. By doing so, it is
possible to simply pick up the sound.
[0022]
This speaker system exhibits flat frequency characteristics over a wide range without its
frequency characteristics being biased to the low frequency side. Therefore, if playback of the
recording source is performed using this speaker system, it will inevitably be possible to hear
sounds very close to the content of the actual recording, and it will be possible to record in a
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6
general household as well as in concert halls, theaters etc. It becomes possible to hear a sound
very close to the content. Of course, if the original sound of the recording source used here is
recorded after the sound field correction by the above-described sound field correction method
of the present invention, it is possible to hear a sound as close as possible to the sound played by
the player. It goes without saying that
[0023]
Furthermore, according to the present invention, there is provided an acoustic system including a
configuration in which the speaker is connected with correction means for putting the sound
pressure level of the sound collected immediately before the speaker within about ± 4 dB over
substantially the entire audio frequency band. It is characterized by
[0024]
This sound system outputs a sound faithful to the original sound in which the influence of the
low-range sound pressure level rise is added or reflected, and the desired sound receiving point
while eliminating or effectively reflecting the influence of the reflected sound in the room It is
possible to realize the sound pickup in the above in combination with a conventional speaker.
In this case, the acoustic system comprises correction means for putting the sound pressure level
of the sound collected immediately before the speaker within about ± 4 dB over substantially
the entire audio frequency band, the speaker and the desired sound receiving point. It is
preferable to include a configuration in which a sound pressure level of the collected sound is
connected to a second correction means for covering the sound pressure level of the collected
sound in substantially the entire audio frequency band within about ± 4 dB.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a sound field
correction method, a speaker system and an acoustic system according to the present invention
will be described below with reference to the drawings.
[0026]
The sound field correction method according to the present invention comprises sound field
correction A shown in FIG. 1 and sound field correction B shown in FIG.
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[0027]
The sound field correction A is performed on the sound output from the monitor speaker 1 in the
following manner, as shown in FIG.
First, pink noise (with constant acoustic energy at equal octave intervals over the entire audio
frequency band) is output from the speaker 1 via the power amplifier 2, and it is installed
immediately before the speaker 1 as a sound collecting means. Sound is collected by the
directional microphone 3.
Next, while observing the waveform of the electrical signal corresponding to the collected sound
by the spectrum analyzer 4, the sound pressure level of the sound collected by the equalizer 5 as
the first correction means is in the audible frequency band (20 Hz to 20 kHz It is performed by
adjusting to be within ± 4 dB over the entire area of).
[0028]
The sound field correction A performed here is characterized in that, as shown in FIG. 3 and FIG.
4, the microphone 3 picks up the sound output from the speaker 1 immediately before that.
[0029]
As mentioned above, the term “immediately before” means within the range of the so-called
near sound field of the speaker to be measured.
Specifically, taking the case of a 2-way closed type in which the diameter of a commonly used
woofer is about 20 cm as in the speaker 1 shown in FIG. 3, the distance w1 from the front of the
cabinet 1a is about 20 cm It means a space that falls within.
[0030]
Then, the sound output from the speaker 1 is collected within this range, and the frequency
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8
characteristic of the sound is adjusted to be within ± 4 dB over substantially the entire audio
frequency band. At this time, for each unit of the woofer 1b and the tweeter 1c, the distribution
of the sound output while observing the waveform of the analyzer 4 is examined while
appropriately moving the microphone 3 in the front of the unit. In consideration of the
distribution of After adjustment of the sound frequency band, the microphone 3 is placed at an
appropriate position.
[0031]
In this case, a full-range speaker 11 with a 20 cm diameter as shown in FIG. 5A can be used
instead of the speaker 1, but at this time the woofer 11a at a position where the distance w2
from the cabinet is within about 20 cm. The microphone 3 is placed at a position on the central
axis of
[0032]
In the case of the speaker 21 provided with the double woofers 21a and 21a and the horn 21b as
shown in FIG. 6B, the sound distribution is on the front of one woofer 21a and a portion
substantially between the two woofers 21a and 21a Of the horn 21b as well as the sound
distribution.
[0033]
Further, as shown in FIG. 6C, in the case of the full range bass reflex type speaker 22, this is
performed while examining the distribution of sound at the front of the port 22a and the woofer
22b.
Furthermore, as in the case of the multi-way speaker 23, as shown in FIG. 6D, the same operation
is performed for each unit of the woofer 23a, the squawker 23b, the high frequency horn driver
23c, and the super tweeter 23d.
In short, this is done by examining the distribution of the sound output for each unit (woofer,
tweeter, squawker, bass reflex type port, horn, etc.) of the speaker to be measured.
[0034]
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9
As described above, to pick up sound immediately before the speaker 1 means that the waveform
of the sound immediately after being output from the speaker 1 to the analyzer 4 appears almost
as it is. Therefore, in the sound field correction A, the sound pressure level of the sound output
from the speaker is substantially spread over the substantially entire audio frequency band by
adding or reflecting the increase of the sound pressure level in the low band immediately after
the output. It can be made flat, which makes it possible to output a sound very close to the
original sound.
[0035]
There is no particular limitation on the speaker 1 used in the sound field correction A, and a
normal speaker can be used. The power amplifier 2 may be a pre-main amplifier integrated with
a control amplifier. The analyzer 4 can also use both pink noise oscillation and white noise
oscillation.
[0036]
The equalizer 5 can adjust the adjustment of the sound pressure level over substantially the
entire audio frequency band, for example, graphic equalizer, parametric equalizer, etc. can be
used, and either analog system or digital system is used can do. In addition, a low pass filter, a
high pass filter, a resonance circuit, etc. can also be used. In the case of using a low pass filter, a
high pass filter, and a resonant circuit, these and a network circuit can be used in combination.
[0037]
The microphone 3 is preferably non-directional and capable of picking up a wide range of sound
as much as possible, and has good sensitivity. For example, it is preferable to use a dynamic or
condenser microphone.
[0038]
After the sound field correction A for the speaker 1 is completed as described above, the sound
field correction B at each sound receiving point is performed as shown in FIG.
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10
Sound field correction B performed here is compared with the above-mentioned sound field
correction A, and the point which newly installed the equalizer 6 used as the 2nd correction
means between the power amplifier 2 and the equalizer 5 on the connection structure of the
apparatus to be used The difference is that microphones 3 are installed at the respective sound
receiving points where sound field correction is to be performed. Here, the newly added equalizer
6 may be the same as, or different from, the existing equalizer 5.
[0039]
When the sound field correction B is performed, first, with the equalizer 5 used for the
adjustment in the sound field correction A as it is, the sound pickup microphone 3 is transferred
to a desired sound reception point. Then, pink noise is output b from the speaker 1 via the power
amplifier 2 and collected by the microphone 3. Next, while observing the waveform of the
electrical signal corresponding to the sound collected by the analyzer 4, the equalizer 6 adjusts
the sound pressure level to be within ± 4 dB over substantially the entire audio frequency band.
[0040]
By performing the sound field correction A, the sound output from the speaker 1 is adjusted to a
sound very close to the original sound after adding or reflecting the influence of the increase of
the sound pressure level in the low frequency range. This adjustment is performed by the
equalizer 5. For this reason, by using the equalizer 5 as it is, the equalizer 6 can appropriately
adjust the change in the characteristic accompanying the transfer of the installation place of the
microphone 3 from the position immediately before the speaker 1 to the desired sound receiving
point. It becomes.
[0041]
That is, no matter where the microphone 3 is installed, the characteristic of the sound collected
at each receiving point is reflected by adjusting the change in the characteristic accompanying
the transfer from the position immediately before the speaker 1 with the equalizer 6 It can be
made to be very close to the original sound by removing the influence of. In this case, even in an
indoor space such as a concert hall or a theater where the influence of the reflected sound is
large, it is possible to pick up a sound faithful to the original sound of the speaker in the room
08-05-2019
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reverberation. This is because two corrections are performed by the equalizer 5 and the equalizer
6, and the correction in consideration of the reflection of the sound in the indoor space can be
freely performed by the equalizer 6 as the second correction means.
[0042]
On the other hand, the equalizer 5 is a correction means for putting the sound pressure level of
the sound collected immediately before the speaker 1 within about ± 4 dB over substantially the
entire audio frequency band. As shown in FIG. 6, an equalizer circuit 7 having a corresponding
function can be incorporated in the speaker 1 to form a speaker 31 as a speaker system.
[0043]
The equalizer circuit 7 can use a low pass filter, a high pass filter, or a resonant circuit.
With this speaker 31, the sound field correction of the present invention can be performed
without using the equalizer 5. When using a low pass filter, a high pass filter, and a resonant
circuit, these and a network circuit can be used together.
[0044]
Then, the speaker 31 can be used instead of the speaker 1. In this case, when the device is
connected as shown in FIG. 1, and the equalizer 5 shown in FIG. 1 is used as the equalizer 6 as
the second correction means. good.
[0045]
In addition, without incorporating the equalizer circuit 7 in the speaker 1, as shown in FIG. 7, the
dedicated equalizer 8 can be provided separately.
This dedicated equalizer 8 serves as a correction means for putting the sound pressure level of
the sound collected immediately before the speaker 1 within about ± 4 dB over substantially the
entire audio frequency band, and the corrected value obtained through this In order to supply a
signal to the speaker 1 through the power amplifier 2, each device can be connected to configure
an acoustic system.
08-05-2019
12
[0046]
EXPERIMENTAL EXAMPLE An experiment conducted to compare the characteristics of the sound
corrected by the sound field correction method of the present invention with the characteristics
of the sound corrected by the conventional method will now be described. In this experiment,
each device is connected and configured according to the above-mentioned FIG. 1 and FIG. 2, and
these are connected to the music listening room of NHK (Japan Broadcasting Corporation) (width
x depth x height: about 5 m x about 5 m x about 2.). It was installed in a room with a sound
absorption of 5 m. The specifications of the names of major equipment used in this experiment
are as follows. Speaker 1: DS-3002 (monitor speaker for broadcasting: manufactured by
Mitsubishi Electric Corp.) 30 cm woofer and domed tweeter two-way spectrum analyzer 4: SA-27
(manufactured by RION) equalizer 5 and 6: YDP-2006 Parametric equalizer: manufactured by
Yamaha
[0047]
FIGS. 8 to 14 show results of measuring the characteristics of the collected sound with the
analyzer 4 by collecting the pink noise output from the speaker 1 with the microphone 3
installed at each point. In each figure, (A) shows the sound pressure level (dB) on the vertical axis
and the frequency (Hz) on the horizontal axis, and shows the frequency characteristics of the
collected sound in a bar graph, and (B) shows each main It shows the numerical value of the
sound pressure level for each frequency.
[0048]
8 and 9 show the results of installing the microphone 3 at a distance of 20 cm just before the
speaker 1 and collecting the sound without correction by the equalizer 5. FIG. 8 shows the center
axis of the woofer, FIG. It shows the result of measurement on the central axis of the tweeter. The
results corrected by the equalizer 5 based on these results are shown in FIGS. 10 and 11,
respectively. By comparing FIG. 8 with FIG. 10, as shown in FIG. 8, the sound pressure level
which had a difference from −1.6 dB (50 Hz) to 3.9 dB (200 Hz) between 50 Hz and 1.0 kHz
was It is understood that after correction, as shown in FIG. 10, it is within the range of -1.6 dB
(500 Hz) to 1.6 dB (100 Hz).
08-05-2019
13
[0049]
Subsequently, the microphone 3 is installed at a point 2 m away from the speaker 1 and located
on the central axis of a portion substantially intermediate between the woofer and the tweeter,
and the same measurement is performed. The measurement results after the second stage
correction are shown in FIG.
[0050]
In FIG. 12, a considerable difference is seen in the sound pressure level of each frequency as a
whole, and the difference of about 11 dB from -6.1 dB (80 Hz) to 5.4 dB (1.6 kHz) opens between
50 Hz and 20 kHz. It is understood that it has been
On the other hand, in FIG. 13, the sound pressure level of each frequency is flat with no
difference overall, and about ± 3 dB from -2.5 dB (160 Hz) to 2.4 dB (63 Hz) between 50 Hz and
20 kHz. It is understood that it is contained within the scope of If an advanced (high
performance) equalizer is used, it is also possible to bring the corrected frequency close to ± 0
dB.
[0051]
Therefore, by performing correction by connecting the equalizer 6, the conventional frequency
characteristic is clearly improved, and the sound output from the speaker 1 is made flat over
substantially the entire audio frequency band. It is understood that a sound very close to the
original sound is outputted from the speaker 1 and such a sound is picked up at a desired sound
receiving point.
[0052]
As a reference example, in FIG. 14, the microphone 3 is placed at a distance of 1 m from the
speaker 1 and located at the center axis of the portion approximately halfway between the
woofer and the tweeter, and only one equalizer is used as in the prior art. The results of the
correction are shown.
This result also shows a considerable difference in the sound pressure level of each frequency,
08-05-2019
14
and the difference of about 8 dB opens from -2.4 dB (80 Hz) to 5.5 dB (1.6 kHz) between 50 Hz
and 20 kHz. It is understood that
[0053]
By the way, in general, the frequency characteristic of the speaker differs depending on the
model, and in particular, the reproduction capability in the low band differs depending on the
aperture of the woofer. Therefore, when using a speaker whose reproduction performance in the
low range is not very high, the low range frequency (the specific frequency varies depending on
the model, but was used in the above experiment when correcting with the first stage equalizer 5
In the case of a speaker, it is preferable to perform the correction with the second stage equalizer
6 collectively without performing the correction of about 40 Hz or less. If the correction
exceeding the reproduction capability of the speaker is made extremely, the speaker may be
adversely affected.
[0054]
The results of experiments conducted in consideration of this point are shown in FIGS. FIG. 15
shows the case where the microphone 3 is installed on the center axis of the woofer at a point 20
cm immediately before the speaker 1, and FIG. 16 similarly shows the case where the
microphones 3 are installed on the center axis of the tweeter. Shows the result of As illustrated,
in the first stage correction by the equalizer 5, the correction of 50 Hz to 20 kHz is performed
without performing the correction of 40 Hz or less.
[0055]
Next, the microphone 3 was placed 2 m away from the speaker 1 at a point located on the central
axis of the approximate middle portion of the woofer and tweeter, and the same measurement
was performed. The results are shown in FIG. As shown in FIG. 17, it is understood that although
a slight variation is seen on the low frequency side compared to the above experimental result
(FIG. 13), a substantially flat frequency characteristic is obtained.
[0056]
Brief description of the drawings
08-05-2019
15
[0057]
1 is a front view showing the apparatus configuration of one step of the sound field correction
method of the present invention.
[0058]
2 is a front view showing the apparatus configuration when performing the subsequent steps of
FIG.
[0059]
3 is an enlarged perspective view of the main part of FIG.
[0060]
4 is an explanatory view showing a positional relationship between a speaker and a microphone
in the sound field correction method of FIG.
[0061]
FIG. 5A is an explanatory view showing the positional relationship between the full-range speaker
and the microphone, FIG. 5B is an explanatory view showing a tablet woofer type, FIG. 5C shows
a bass reflex type speaker, and FIG. .
[0062]
6 is an internal circuit configuration diagram showing an example of a speaker equipped with the
correction means.
[0063]
7 is a circuit diagram showing another speaker different from FIG.
[0064]
8 shows characteristics of the sound before correction collected on the central axis of the 20 cm
woofer from the speaker, (A) shows frequency characteristics, (B) shows numerical values of
sound pressure levels for respective frequencies.
08-05-2019
16
[0065]
Similarly to FIG. 9, the results of measurement on the central axis of the tweeter are shown, in
which (A) shows frequency characteristics and (B) shows numerical values of sound pressure
levels for respective frequencies.
[0066]
FIG. 10 shows corrected characteristics of the sound collected at the same position as FIG. 8,
where (A) shows frequency characteristics and (B) shows numerical values of sound pressure
levels for respective frequencies.
[0067]
FIG. 11 shows the corrected sound characteristics of the sound collected at the same position as
FIG. 9, where (A) shows frequency characteristics, and (B) shows numerical values of sound
pressure level for each frequency.
[0068]
Fig. 12 shows the characteristics of the sound collected at 2 m from the speaker, where (A) is a
frequency characteristic, and (B) is a numerical value of the sound pressure level for each
frequency.
[0069]
FIG. 13 is a graph showing the characteristics of the corrected sound of the equalizer as the
second correction means, in which (A) shows frequency characteristics, and (B) shows numerical
values of sound pressure levels for respective frequencies.
[0070]
FIG. 14 shows corrected characteristics of the sound collected at 1 m from the speaker, where (A)
is a frequency characteristic, and (B) is a numerical value of the sound pressure level for each
frequency.
[0071]
FIG. 15 shows the corrected characteristics of the sound collected on the central axis of the 20
cm woofer from the speaker, where (A) is a frequency characteristic and (B) is a numerical value
of the sound pressure level for each frequency.
08-05-2019
17
[0072]
FIG. 16 shows the corrected characteristics of the sound collected on the central axis of the
tweeter, in which (A) shows frequency characteristics, and (B) shows numerical values of sound
pressure level for each frequency.
[0073]
Fig. 17 shows the characteristics of the corrected sound of the equalizer which is the second
correction means of the sound collected at 2 m from the speaker, (A) shows the frequency
characteristics, (B) shows the sound pressure level for each frequency It is a figure showing a
numerical value
[0074]
FIG. 18 is an explanatory view showing a method of measuring the specification of the
conventional speaker.
[0075]
FIG. 19 shows the increase in sound pressure level of the sound collected immediately before the
speaker, where (A) is a frequency characteristic, and (B) is a numerical value of the sound
pressure level for each frequency.
[0076]
Explanation of sign
[0077]
A, B sound field correction 1, 11, 12, 21 speaker 22, 23, 31 speaker 2 power amplifier 3
microphone 4 spectrum analyzer 5, 6 equalizer 7 equalizer circuit 8 equalizer
08-05-2019
18
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