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JP2003075245

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DESCRIPTION JP2003075245
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
technique for correcting a sound wave selectively picked up from a moving sound source using a
microphone array.
[0002]
2. Description of the Related Art A sound collecting device is known which obtains directivity by
weighted averaging of signal outputs of sound waves collected by microphones using a
microphone array. In the conventional sound pickup apparatus, a plane wave was assumed as the
incident wave. Assuming that the distance | x | from the sound source to the measurement
position is 20 m, the size l of the sound source is sufficiently small, and the wavelength of the
sound wave is λ, acoustic far-field conditions | x | >> λ and the acoustic compact condition λ
>> l are satisfied. Therefore, it relies on the fact that the incident wave to the microphone can be
regarded as a plane wave. Such a sound collecting device is described, for example, in Japanese
Patent No. 1134369. Further, a correction method in the case where the sound source is
positioned in a direction other than the direction perpendicular to the axis of the microphone
array is disclosed in JP-A-5-91588.
[0003]
04-05-2019
1
However, in the case of low-frequency sound (where λ is relatively large), the acoustic compact
condition is considered to hold, but the acoustic far-field condition does not hold. . Therefore,
when collecting low frequency sound, it can not be considered as a plane wave. Also, even when
the distance from the sound source to the measurement position is small compared to the
frequency of the sound wave to be collected, the acoustic far-field condition does not hold
similarly, so it can not be regarded as a plane wave as well. Under such conditions, when a sound
wave is measured as a plane wave, there is a problem that the directivity characteristic is
degraded. The present invention is a device having an appropriate directivity characteristic even
when the sound wave can not be considered as a plane wave, such as when the wavelength is
relatively long or when the distance between the sound source and the measurement position is
relatively short. Intended to provide.
[0004]
SUMMARY OF THE INVENTION A sound measurement and analysis apparatus for obtaining
directivity by superposing outputs of microphones of a microphone array in which a plurality of
microphones are arranged on a substantially straight line, which comprises: A band pass filter for
filtering each output with a filter having predetermined characteristics including a center
frequency to be acquired, a sound source as a nonpolarity monopole point sound source, and a
sound wave incident on a microphone as a spherical wave Under the assumption that the
correction means for correcting the amplitude and phase of the filtered output based on the
relative position of each of the microphones to the sound source, and the superimposed
waveform by superimposing the waveform corrected by the correction means And waveform
weighting means for obtaining .mu.
[0005]
In a preferred embodiment, of the outputs from the microphone, further, at equal intervals along
a straight line, the (n) th such interval is 1⁄2 of the wavelength λ c of the sound wave of the
center frequency. No. 0 No.... An acquiring means for acquiring an output from the (n + 1) th (2n
+ 1) microphones, wherein the correcting means relates to each of the outputs acquired by the
acquiring means 1) The amplitude of the sound pressure pj observed by the j-th microphone is
multiplied by qj, and (2) the acquisition time of the sound pressure pj observed by the j-th
microphone is s (qj-1) / Delay by c0 (where q j = (1 + (j λ c / 2 s) 2) 1/2, s is the position of the
0th microphone and the 0th microphone on a straight line along the microphone array Extend
from the position of The distance between the intersection of the straight line and parallel to the
straight line passing through the line and the sound source, c0 is the sound velocity) manner, is
configured so as to correct the amplitude and phase.
04-05-2019
2
In the present specification, “acquisition time” does not mean the time for actually acquiring
the emitted sound wave, but changes the time axis in the data as if the acquisition time is
delayed, for example. It means that.
[0006]
In the above embodiment, the sound wave of the microphone is acquired such that the distance
between the microphones to be used is a half wavelength of the sound wave of the center
frequency to be analyzed. According to the above embodiment, when the sound source is fixed, it
is possible to obtain a good superimposed waveform of the directional characteristics.
[0007]
In another preferred embodiment of the present invention, the output from the microphones is
equally spaced on a straight line such that the interval is 1⁄2 of the wavelength λ c of the sound
wave of the center frequency. n) No. 0: No. 0: obtaining means for obtaining an output from (n +
1) th (2n + 1) microphones, the correction means relates to each of the outputs obtained by the
obtaining means , (1) The amplitude of the sound pressure pj observed by the j-th microphone is
multiplied by qj, and (2) the acquisition time of the sound pressure pj observed by the j-th
microphone is s (qj-1 ) / C 0 (where q j is the equation shown in Equation 5 below, s is the
position of the 0th microphone and the 0th microphone on a straight line along the microphone
array) Hanging from the position The distance between the line and the point of intersection of
the straight line passing through the sound source and the straight line parallel to it, c0 is the
speed of sound, U is the moving speed of the sound source, M = U / c0), so as to correct its
amplitude and phase. It is configured. According to this embodiment, when the sound source
moves, by installing the microphone array so as to be parallel to the moving direction, it is
possible to obtain a superimposed waveform with a good directional characteristic. .
[0008]
In another preferred embodiment, of the outputs from the microphones, the intervals are a half
of the wavelength λc of the sound wave of the center frequency at equal intervals on a straight
line. (-N) No.... No. 0... An acquisition means for acquiring an output from (n) th (2n + 1)
microphones, wherein the correction means is an output of the output means acquired by the
04-05-2019
3
acquisition means For each, (1) the amplitude of the sound pressure pj observed by the j-th
microphone is multiplied by qj (1-M cos Θ oj) 2 and (2) acquisition of the sound pressure pj
observed by the j-th microphone The time is delayed by s (qj-1) / c0 and its frequency is
multiplied by (1-M cos Θ oj), where q j is a formula shown in the following equation 6, and s is
the 0th microphone. Position and the The distance between the vertical line extending from the
position of the 0th microphone and the straight line parallel to the straight line passing through
the sound source, c0 is the speed of sound, and U is the movement of the sound source The
velocity, M = U / c0, Θoj, where t = 0 is the time when the sound source passes the
perpendicular line of the straight line extending from the 0th microphone, t = s from the time
when the sound wave is emitted from the sound source To correct the amplitude and phase so
that the direction vector when looking at the jth microphone from the position of the sound
source at time t when / c0 has elapsed and the direction vector that coincides with the moving
direction of the sound source It is configured. ## EQU6 ## In this embodiment, it is possible to
obtain superimposed waveforms with good directional characteristics, taking into consideration
the Doppler coefficient. Furthermore, the object of the present invention is also achieved by a
sonometry analysis program which causes a computer to function as each means described
above.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing
a schematic configuration of a sonic measurement analysis system according to the present
invention. As shown in FIG. 1, in this sonic measurement analysis system, (2n + 1) microphones
14-(-n), 14- (n-1), ..., 14-0, ... in the axial direction. , 14-n are connected to the data recorder 16.
The microphone array 12 is configured by the (2n + 1) microphones. In the present embodiment,
a so-called micro-pressure gauge is used as a microphone so that low-frequency sound can be
measured.
[0010]
Further, in the present embodiment, signals collected by (2n + 1) microphones are applied to the
data recorder 16, and signals from the respective microphones 14 are accumulated in the data
recorder. Also, a processing device 18 is connected to the data recorder 16.
[0011]
04-05-2019
4
The processing unit 18 receives an acoustic signal collected by each microphone 14 from the
data recorder 16 and digitizes the acoustic signal, and the A / D converter 20 and the data
subjected to the calibration process. And a band pass filter (BPF) 22 which executes band pass
filter processing, a correction processing unit 24 which executes necessary correction processing
considering that the given waveform is a spherical wave, and And a composite waveform
generation unit 26 for converting the superimposed waveform into a physical quantity indicating
power. The processing unit 18 further includes an input unit 28 such as a keyboard and a mouse,
a display unit 30 such as a CRT, and a processing control unit 32 for controlling various
components in the processing unit and processing thereof.
[0012]
The processor 18 according to the present embodiment can be realized by a personal computer.
By installing the processing program stored in the CD-ROM in the personal computer, it is
possible to realize the function.
[0013]
[Principle of the Invention] Before describing the processing in the acoustic measurement and
analysis system configured as described above, the principle of the present invention will be
described below. First, assuming that the incident wave is a plane wave, as shown in FIG. 2, the (n) th, the (-n + 1) th,..., The 0th (zero) th,. The (2n + 1) microphones of are disposed at equal
intervals d on the axis 200, and it is considered that sound waves are incident from a direction
deviated from the direction perpendicular to the axis 200 by an angle θ. Here, the microphone
distance d and the wavelength λc of the incident wave are set so as to satisfy the following
relationship. In FIG. 2, the distance between the wavefronts 201 and 202 corresponds to the
wavelength λ c of the incident wave. d = λc / 2 (1.1)
[0014]
Since the incident wave is assumed to be a plane wave, the sound pressure pj observed by the jth microphone (see reference numeral 201) is expressed by the following equation. Here, A, ω
and ψ j respectively indicate the amplitude of the incident wave, the angular frequency, and the
04-05-2019
5
phase difference at the j-th microphone 14-j. Assuming that the phase difference in the 0th
microphone 14-0 is "0 (zero)", the phase difference of the jth microphone is given by ψ j = 0 0 j
(λ c / 2) sin θ (1.3). However, it is κ0 = ω / c0 (1.4). However, when ωc is an angular
frequency corresponding to λc and the dimensionless angular frequency Ω is defined as Ω = ω
/ ωc (1.5), the above equation (1.4) becomes κ0 = κcΩ (1.6) Equation (1.2) can be modified as
follows using equations (1.3) and (1.6). [Equation 8]
[0015]
Assuming that the weight of the j-th microphone is w j, a weighted superposition waveform P (θ,
Ω) in which the outputs of the respective microphones are superposed can be expressed as
follows. [Equation 9]
[0016]
Taking the square of this absolute value, the following equation is obtained, and the value of
equation (1.9) when θ = 0 is: | P (0, Ω) | 2 = A 2 (1.10) ). Thereby, the directivity characteristic
K2 (θ, Ω) of the weighted superimposed waveform can be expressed as follows. [Equation 11]
[0017]
The value obtained by multiplying the common logarithm of the above equation (1.11) by 10
provides the sensitivity characteristic in decibel display. In FIG. 3, to each microphone of the
microphone array consisting of five microphones, microphone weights of predetermined weights
(for example, both ends (numbers (-2) and 2): weight of 0.125, remainder (number -1) is a graph
calculated by setting the weight of the microphone of No. 0, No. 0 and No. 1): 0.25). In FIG. 3, the
center frequency corresponds to equation (1.11).
[0018]
[Fixed Point Sound Source] On the other hand, in the present invention, a spherical wave is
assumed as the incident sound wave. First, as shown in FIG. 4, a description will be added on the
assumption that the sound source is a monopole point sound source having no directivity.
04-05-2019
6
Assuming a spherical wave, the sound pressure pj observed by the j-th microphone in FIG. 4 can
be expressed as follows. Where x j and y are the position of the observation point, ie, the j-th
microphone, and the position of the sound source S, respectively, and are given as follows. xj = (j
(λc / 2), 0,0) (2.2) y = (s * tan θ, s, 0) (2.3) where s is the position of the 0th microphone, The
distance between the vertical line extending from the position of the zeroth microphone and the
intersection point of the sound source S and a line parallel to the axis of the microphone, and θ
is the position of the normal line and the position of the zeroth microphone It is an angle formed
by a straight line extending to the sound source S.
[0019]
The distance | xj−y | between the observation point and the sound source can be expressed by
the following equation (13) using the equations (2.1) and (2.2). Here, when equation (2.4) is
transformed, | xj−y | becomes as follows. Using equation (2.5), equation (2.1) is expressed as
follows: [Equation 15]
[0020]
Therefore, a weighted superposition waveform P (θ, Ω) in which the outputs pj of the respective
microphones are superposed is expressed as follows. The square of the absolute value of P (θ,
Ω) expressed by equation (2.9) is: ## EQU17 ## and when θ = 0 in equation (2.10) above, α j
Since (0) = 1, the following equation is obtained. Therefore, the directivity characteristic K2 (θ,
Ω) of the weighted superimposed waveform can be expressed as follows. [Equation 19]
[0021]
FIG. 5 and FIG. 6 are graphs showing directivity specification Koct2 of the octave band calculated
based on the directivity characteristic shown by the above equation (2.12). In FIGS. 5 (a) and 5
(b) and FIGS. 6 (a) and 6 (b), "s = ** m" described at the lower right of the graph indicates the
distance from the sound source. It will be understood from these graphs that as the distance s
from the sound source becomes shorter, and as the frequency of the sound source becomes
lower, the directivity characteristic of the microphone array gets worse.
[0022]
04-05-2019
7
In the case of a plane wave, when the incident angle of the sound wave is 0 °, the amplitudes
(distance attenuation) and phases of the sound waves measured by the respective microphones
are aligned. On the other hand, in the case of a spherical wave, as shown in FIG. 7, since the
wavefront 702 is spherical (circular in FIG. 7) even if the incident angle is 0.degree. Because the
phase is different, the directivity characteristic is degraded. Therefore, for example, when the
incident angle is 0 °, that is, when the sound source is located in front, it is possible to suppress
the deterioration of the directional characteristic by correcting so that the amplitude and phase
in each microphone are aligned. In the present specification, this is referred to as "spherical wave
correction".
[0023]
First, consider the amount of correction to the amplitude. In FIG. 7, assuming that the distance
between the 0th microphone and the sound source S is s, the distance R0j between the jth
microphone and the sound source S can be expressed by the following equation (3.1) . Therefore,
the correction amount q j for making the amplitudes of the sound waves arriving at the 0th
microphone and the sound waves arriving at the jth microphone can be determined as follows.
[Equation 21]
[0024]
Next, consider the phase correction amount. The distance R0j between the j-th microphone and
the sound source S and the difference ΔRj between the zero-th microphone and the sound
source S can be expressed by the following equation. Therefore, when the sound wave having the
same phase as the sound wave reaching the 0th microphone reaches the jth microphone,
assuming that the sound velocity is c0, Δt = (s / c0) (qj-1) The time is delayed by (3.4).
Therefore, in order to align the phases of the sound waves reaching the microphones, the
acquisition time of the sound pressure of the j-th microphone may be delayed by Δt.
[0025]
Therefore, in the present invention, (1) the amplitude of the sound pressure pj observed by the jth microphone is multiplied by qj, and (2) the sound pressure pj observed by the j-th microphone
04-05-2019
8
The acquisition time is delayed by s (qj-1) / c0. When corrected as described above in equation
(2.1), the corrected sound pressure pj 'is as follows. [Equation 23]
[0026]
Substituting the equations (1.6) and (2.5) into the equation (3.5) gives the equation (3.6). Further,
a weighted superimposed waveform P ′ (θ, Ω) obtained by superposing the outputs of the
microphones based on Equation (3.6) is as shown in Equation (3.7). The square of the absolute
value of the above equation (3.7) can be obtained as in equation (3.8). In the equation (3.8), the
value of θ = 0 is αj (0) = 1 and Σ (j = −n, −n + 1,..., 0,... N) wj = 1 Therefore, | P ′ (0, Ω) | 2 =
A2 / s2 (3.9).
[0027]
Thus, the directivity characteristic (K '(.theta., .OMEGA.)) 2 of the weighted superposition
waveform after the spherical wave correction can be obtained as follows. [Equation 26]
[0028]
FIGS. 8 and 9 are graphs showing directivity characteristics Koct2 of an octave band calculated
based on the directivity characteristics shown in equation (3.10). In FIGS. 8A and 8B and FIGS. 9A
and 9B, “s = ** m” described at the lower right of the graph indicates the distance from the
sound source. By comparing FIGS. 8 and 9 with FIGS. 5 and 6, it can be understood that the
spherical wave correction improves the directivity of the microphone array.
[0029]
Moving Point Sound Source Furthermore, in the present invention, spherical wave correction can
be performed in consideration of movement of the point sound source. This principle will be
described below. Also for the moving point sound source, (1) the amplitude of the sound pressure
pj observed by the j-th microphone is multiplied by qj and (2) the acquisition time of the sound
pressure pj observed by the j-th microphone It is based on delaying by s (qj-1) / c0. However, for
the amplitude qj, the following equation is used. [Equation 27]
04-05-2019
9
[0030]
Here, M is the Mach number of the sound source S. Assuming that the moving speed of the
sound source S is U and the sound speed is c0, M is defined as M = U / c0. When the sound
source S moves, the angle between the vector connecting the jth microphone and the sound
source and the vector in the movement direction of the sound source changes. In equation (4.2),
Θ j is a direction vector (see symbol 1001 in FIG. 10) when looking at the observation point of
the j-th microphone from the sound source S at time t and a direction vector (in the direction of
movement of the sound source The angle with respect to the reference numeral 1002 in FIG. 10
is shown (see FIG. 10). When spherical wave correction is performed on the sound pressure pj (t)
of the moving sound source S represented by equation (4.2), the corrected sound pressure pj ′
(t) is represented as equation (4.3) be able to. [Equation 28]
[0031]
By rearranging the equation (4.3), the corrected sound pressure pj '(t) can be expressed as
follows. Therefore, the weighted superposition waveform P '(t, Ω) in which the outputs of the
respective microphones are superposed can be expressed as follows. [Equation 30]
[0032]
The square of the absolute value of the weighted superimposed waveform is expressed by
equation (4.8). Here, in equation 4.8, when the value of t = s / c0 is expressed as cos Θ j when
cos Θ j at t = s / c 0, α j (s / c 0) = 1, so It becomes like 4.9). [Equation 31]
[0033]
Thus, the directivity (K '(t, Ω)) 2 of the weighted superposition waveform can be expressed as
follows. Even when the moving point sound source moves, basically (1) the amplitude of the
sound pressure pj observed by the j-th microphone is multiplied by q j, and (2) the j-th The
correction is realized by delaying the acquisition time of the sound pressure pj observed by the
microphone of the above by s (qj-1) / c0. However, qj takes into consideration the Mach number
04-05-2019
10
as shown in equation (4.1). FIG. 11 is a graph showing the directivity characteristics of the octave
band calculated based on the directivity characteristics shown in equation (4.10). FIG. 11A shows
the characteristics at center frequencies of 31.5 Hz, 16 Hz and 8 Hz when the distance s from the
sound source is 32.088 m and the velocity of the moving point sound source is set to 100 km.
[0034]
In FIGS. 11 (b) and 11 (c), the distance from the sound source and the center frequency are the
same as in FIG. 11 (a), while the speed of the point sound source is 300 km and 500 km,
respectively. It can be seen from FIG. 11 that relatively good characteristics are obtained even if
the speed of the point sound source is high.
[0035]
[Description of Specific Operation of System] In the present embodiment, the following
processing is performed using the above principle. Here, sound waves emitted from a sound
source moving on a substantially straight line are collected at a predetermined speed. FIG. 12 is a
diagram showing the structure of the microphone array used in the present embodiment. Here, a
microphone array is arranged to pick up low frequencies emitted from a train traveling on the
track. As shown in FIG. 12, the microphone array 1200 is arranged such that its axis is parallel to
the line 1210. In the present embodiment, nine microphones 14-1 to 14-9 are arranged in the
microphone array 1200. Note that this microphone array is not referred to as the n-th
microphone, but is referred to as a 1-ch microphone, a 2-ch microphone,.
[0036]
In this embodiment, in order to pick up sound waves of 31.5 Hz, 16 Hz and 8 Hz, the microphone
spacing is d1 = 5.397 m, 2 ch, 3 ch between 3 ch to 7 ch microphones. Between the 5ch, 7ch and
8ch microphones, d2 = 10.625m, 1ch, 2ch, 5ch, 8ch and 9ch microphones, d3 = 21.250m. These
intervals are equal to the half wavelengths λc / 2 of the 31.5 Hz, 16 Hz and 8 Hz sound waves,
respectively. In addition, the distance D between the movement vector of the sound source (see
reference numeral 1210) and each microphone is 32.088.
[0037]
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11
As shown in FIG. 13 which is a flow chart showing the processing procedure, from the train
traveling at about 230 km / hr and the train traveling at about 270-280 km / hr using the
microphone array 1200 arranged as described above. The sound waves emitted and collected by
the microphones 14-1 to 14-9 are recorded in the data recorder 16 (step 1301).
[0038]
Thereafter, the processing control unit 32 of the processing unit 18 issues an instruction or the
like to each component in the processing unit 18 in accordance with an analysis program stored
in a memory or a hard disk drive (not shown). Thus, analysis processing is performed.
The processing unit 18 A / D converts the signal acquired by each microphone 14 recorded in
the data recorder 16 and temporarily stores it, for example, in a memory (not shown) in the
processing unit 18 (step 1302). ). At the time of analysis, the processing unit 18 selects a data set
based on a signal acquired from a predetermined microphone according to the frequency to be
analyzed (step 1303). For example, when the center frequency is 31.5 Hz, a data set based on
signals acquired from 3 to 7 ch microphones is selected.
[0039]
Next, the data making up the selected data set is filtered by the BPF 22 under the characteristics
determined by the center frequency (step 1304). Next, spherical wave correction is performed on
each data in the correction processing unit 24 (step 1305). As described above, in the present
embodiment, (1) the amplitude of the sound pressure pj observed by the j-th microphone is
multiplied by qj and (2) the sound pressure observed by the j-th microphone The acquisition time
of pj is delayed by s (qj-1) / c0. Where s is the distance between the position of the zeroth
microphone and the point of intersection of a vertical line extending from the position of the
zeroth microphone and a line parallel to the axis of the microphone passing through the sound
source S, c0 Is the speed of sound.
[0040]
In the present embodiment, for example, spherical wave correction is possible for each of the
fixed point sound source and the moving point sound source, and the operator sets the operation
04-05-2019
12
mode to perform spherical wave correction under any of the modes. It is desirable to configure it
to perform Here, in the operation mode of the fixed point sound source, q j based on equation
(3.2) is used. In addition, in the operation mode of the moving point sound source, qj based on
the equation (4.1) may be used.
[0041]
Data based on the sound waves acquired from the microphones corrected for spherical waves in
this way is given to the waveform generation unit 26. After superimposing the respective data
(step 1306), the waveform generation unit 26 evaluates the superimposed waveform according
to the following equation (5.1) (here, referred to as "average pointing power waveform") (Step
1307). Where T is a time constant, ρ 0 = 2 × 10 −5 Pa. This takes into consideration that the
acquired raw pressure waveform is complicated and difficult to use. The data generated in this
manner is stored, for example, in a database (not shown) or displayed on the screen of the
display device 30 (step 1308). The average pointing power waveform obtained in step 1308 and
the pointing power waveform obtained by squaring after superposition obtained in the previous
step are compared or further processed to be analyzed. It can be
[0042]
According to the present embodiment, the amplitude and phase of the sound wave from the point
sound source are corrected in consideration of reaching the microphones arranged on the array
as spherical waves. Therefore, it is possible to obtain a superimposed waveform with a good
directional characteristic.
[0043]
FIGS. 14 (a) to 14 (c) show examples of the directivity power waveform without the spherical
wave correction according to this embodiment and the directivity power waveform after the
spherical wave correction. In FIGS. 14 (a) to 14 (c), the broken line indicates the waveform before
the spherical wave correction, and the solid line indicates the waveform after the spherical wave
correction. These are obtained by obtaining a pointing power waveform based on a sound wave
acquired when a vehicle traveling at a speed of 272 km / hour passes. Fig. 14 (a) shows a power
waveform at 31.5 Hz, Fig. 14 (b) at 16 Hz, and Fig. 14 (c) at 8 Hz. It can be understood that the
peak value is larger in the spherical wave-corrected one (see the solid line) by comparing the
04-05-2019
13
peak values when the head portion of the train and the portion where the cover of the
pantograph is located pass. The present invention is not limited to the above embodiment, and
various modifications are possible within the scope of the invention described in the claims, and
they are also included in the scope of the present invention. It goes without saying that
[0044]
For example, in the above embodiment, in the case of the moving point sound source, the
amplitude and phase are corrected without considering the Doppler effect. However, correction
may be performed in consideration of the Doppler effect. In this case, (1) the amplitude of the
sound pressure pj observed by the j-th microphone is multiplied by qj (1-M cos Θ 0 j) 2 and (2)
the sound pressure pj observed by the j-th microphone The acquisition time of s may be delayed
by s (qj-1) / c0 and its frequency may be multiplied by (1-M cos Θ 0 j). However, here, Θoj, Θoj
is a time when the sound source passes through a straight perpendicular line extending from the
0th microphone and the microphone array is extended from t = 0, a sound wave is emitted from
the sound source The direction vector when looking at the jth microphone from the position of
the sound source at time t when t = s / c 0 has elapsed from the time is the angle between the
direction vector that coincides with the moving direction of the sound source.
[0045]
It goes without saying that the number of microphones constituting the microphone array is not
limited to the above embodiment. It is also clear that the spacing of the microphones can also be
changed accordingly according to the frequency of the sound waves to be measured and
analyzed.
[0046]
Furthermore, in the above embodiment, the signal from the microphone 14 is recorded in the
data recorder 16 at one end, and the signal output from the data recorder 16 is digitized by the A
/ D converter 20. The configuration is not limited to such a configuration, and the signal from the
microphone 14 may be directly given to the A / D converter 20 without passing through a data
recorder. In this case, step 1301 is omitted in FIG.
04-05-2019
14
[0047]
According to the present invention, the sound wave can not be considered as a plane wave, for
example, when the wavelength is relatively long or when the distance between the sound source
and the measurement position is relatively short. Also, it is possible to provide a device with
appropriate directional characteristics.
[0048]
Brief description of the drawings
[0049]
FIG. 1 FIG. 1 is a block diagram showing a schematic configuration of a sonic measurement
analysis system according to the present invention.
[0050]
FIG. 2 is a view schematically showing sound waves incident on the respective microphones
when a plane wave is assumed.
[0051]
FIG. 3 is a diagram showing an example of directivity characteristics based on superimposed
waveforms using a microphone array when a plane wave is assumed.
[0052]
FIG. 4 is a view schematically showing sound waves incident on the microphones when the sound
source is considered to be a monopole element point sound source having no directivity.
[0053]
FIG. 5 is a diagram showing an example of the directivity characteristic based on the
superimposed waveform of the waveforms to which the correction according to the present
embodiment is not applied when the spherical wave is assumed.
[0054]
FIG. 6 is a diagram showing an example of the directivity characteristic based on the
superimposed waveform of the waveforms not subjected to the correction according to the
present embodiment when the spherical wave is assumed.
04-05-2019
15
[0055]
FIG. 7 is a view schematically showing a state where a spherical wave from a point sound source
is incident on each microphone.
[0056]
FIG. 8 is a diagram showing an example of the directivity characteristic based on the
superimposed waveform of the waveforms subjected to the correction according to the present
embodiment when a spherical wave is assumed.
[0057]
FIG. 9 is a diagram showing an example of the directivity characteristic based on the
superimposed waveform of the waveforms subjected to the correction according to the present
embodiment when the spherical wave is assumed.
[0058]
FIG. 10 is a view schematically showing a state where a spherical wave from a point sound
source is incident on each microphone when the point sound source moves.
[0059]
FIG. 11 is a diagram showing an example of the directivity characteristic based on the
superimposed waveform of the waveform corrected according to the present embodiment,
assuming a spherical wave radiated from the moving point sound source.
[0060]
FIG. 12 is a diagram showing the structure of the microphone array used in the present
embodiment.
[0061]
FIG. 13 is a flowchart showing the processing procedure executed by the sound wave
measurement and analysis system according to the present embodiment.
[0062]
04-05-2019
16
FIG. 14 is a diagram showing a power waveform based on the superimposed waveform before
and after the correction according to the present embodiment.
[0063]
Explanation of sign
[0064]
12 microphone array 14 microphone 16 data recorder 18 processing device 20 A / D converter
22 BPF 24 correction processing unit 26 waveform generation unit 28 input device 30 display
device 32 processing control unit
04-05-2019
17
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