JP2544535B2 - Measuring device and measuring method for moving sound source - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound source distribution on a moving body such as a railroad car or an automobile when the moving path and the moving direction of the moving body moving while making noise are predicted or measurable at the time of measurement. Related to the device for measuring the noise, especially the noise generation position and intensity distribution of the moving sound source,
The present invention relates to a measuring device for acquiring data for noise reduction, such as wind noise, and detecting position and speed, which are emitted from a moving body.

[0002]

2. Description of the Related Art A typical example of a conventional moving sound source measuring apparatus using a microphone array is Proceedings of Inter Noise 88 (1988), pages 167 to 170, and 1391. More first
396 pages (PROCEEDINGSOF INTER
NOIZE 88 (1988), PP167-170,
PP 1391-1396).

Further, as a typical example of a sound source measuring device for analyzing the strength of a stationary sound source by intersecting a pair of microphone arrays, the Journal of the Acoustical Society of Japan, Vol.
1988), pages 916-922.

[0004]

In the moving sound source measuring apparatus using the microphone array described in the above-mentioned Proceedings of Inter Noise 88 (1988), only one microphone array is used and each microphone is used for capturing. The one-dimensional sound source distribution of the high-speed railway vehicle is obtained by shifting the acoustic signals from the moving sound source by the time of arrival of the sound waves to each microphone and superimposing them. However, one microphone array has no sound source resolution in the direction orthogonal to the array direction of the microphones, and thus has no two-dimensional sound source resolution. Therefore, the accurate sound source distribution on the moving sound source surface cannot be obtained.

The above-mentioned Journal of Acoustical Society of Japan, Vol. 44, No. 12 (1
(1988), a pair of microphone arrays are crossed to analyze the strength of a stationary sound source.
By using an arc-shaped microphone array, the sound source at the center of the arc can be separated from other sound sources, but it is not taken into consideration when the sound source moves relative to the microphone array. It could not be used to measure the sound source distribution on the sound source. In addition, since the interval between the microphones must be narrower than 1/2 of the wavelength of the highest frequency to be measured, when the wavelength is short, the number of microphones increases and the calculation process is heavy.

A first object of the present invention is to provide a moving sound source measuring apparatus or measuring method for accurately measuring a two-dimensional sound source distribution on a moving sound source surface.

A second object of the present invention is to provide a measuring device or a measuring method for a moving sound source, which can reduce the number of microphones to be used without lowering the accuracy.

[0008]

In order to achieve the first object, a measuring device for a moving sound source according to the present invention has a plurality of microphones arranged in an array and a pair of microphone arrays intersect each other. In addition, each of the pair of microphone arrays is arranged in a direction that is not orthogonal to the moving direction of the sound source, and the acoustic signal detected by the microphone is used only for the arrival time of the sound wave from the moving sound source to each microphone. A delay time calculating device for correcting, an adding device for superimposing the corrected signals, a frequency analyzing device for performing frequency analysis of the superimposed signals, and a decibel arithmetic averaging device for averaging the frequency analyzed spectra. It is equipped with.

Also, a pair of microphone arrays are crossed with each other in a cross or V shape.

Further, using a plurality of microphones which are crossed and arranged in a direction not orthogonal to the moving direction of the sound source, the acoustic signals detected by the microphones are transmitted from the moving sound source to the respective microphones at the arrival time of sound waves. The directivity of the microphone is enhanced by shifting and superimposing it, the sound source distribution is measured multiple times while the sound source is moving, and this is averaged to measure the sound source distribution.

Further, based on the result of measuring the sound source a plurality of times while passing through the vicinity of the microphone array, in order to accurately separate the sound source, the strength of the sound source is expressed in decibels, and the average of the measurement results is expressed by It is the arithmetic mean.

Further, in order to measure the speed of the moving sound source with high accuracy, the sounds emitted from two sound sources on the moving sound source whose positions are known in advance are detected by a microphone near the moving sound source, and the moving sound source is detected from the time interval. It calculates speed.

Further, when the outputs of all the microphones on the microphone array cannot be recorded by one measuring device, in order to synchronize a plurality of recording devices, at least one microphone on each recording device should be synchronized. The output is simultaneously recorded on another recording device.

In order to achieve the second object, the moving sound source measuring apparatus of the present invention measures the distance between individual microphones on an array of microphones in order to use as few microphones as possible. It is longer than one half of the wavelength length at the highest frequency of the sound.

Further, the sound source distribution is measured a plurality of times while the sound source is moving, and this is averaged to measure the sound source distribution.

[0016]

[Function] With a single linear microphone array, the acoustic signals captured by the respective microphones are overlapped by shifting the acoustic signals from the moving sound source to be measured to the respective microphones by shifting the arrival time of the acoustic waves. It can be separated from a sound source in another different position. However, it is difficult to separate the sound from two sound sources arranged in a direction perpendicular to the microphone arrangement direction because the difference in the arrival time of the sound wave to each microphone is small due to the difference in the position of the sound source. That is, the sound source resolution is low.
For this reason, one linear microphone array has directivity only in the microphone array direction. Therefore, two-dimensional directivity can be provided by using a pair of microphone arrays and crossing them in a cross or V shape to overlap the directivity characteristics of the respective microphone arrays. This gives 2
It is possible to measure the dimensional sound source distribution.

Further, since the sound source moves, the relative position of the sound source and the microphone array changes as the sound source moves, and the directivity pattern changes. Therefore, in one measurement,
Even if the sound source separation accuracy of two specific points is low, if the sound source resolution is sufficient for the measurement when the sound source moves to another position, the separation accuracy of the two sound sources can be calculated by averaging multiple measurements. It is possible to improve.

The pair of microphone arrays are arranged as close as possible to the front of the moving sound source in order to improve the resolution. At this time, when the pair of microphone arrays are orthogonal to and parallel to the moving direction of the sound source, these arrays always have low resolution in the moving direction of the sound source and in the direction orthogonal to the moving direction. Therefore, even if the measurement is performed a plurality of times while the sound source is moving, it is not possible to improve the separation accuracy of the two sound sources arranged in the moving direction on the moving sound source or in the direction orthogonal to the moving direction. On the other hand, unless both the pair of microphone arrays are orthogonal to the moving direction of the sound source, the direction in which the sound source resolution decreases due to the moving sound source changes. The sound source resolution can be obtained.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an example in which a moving sound source measuring apparatus according to an embodiment of the present invention is applied to search for a noise source of a railway vehicle body. As shown in FIG. 1, the speed detection sensor 5 measures the speed of the railway vehicle 1 on the track 2 at a speed V, for example, when moving linearly, and the microphone array 3 is placed in a plane parallel to the moving direction. Install. The microphone array 3 comprises a pair of V-shaped arrays 3a and 3b arranged substantially orthogonal to each other, and the arrays 3a and 3b are installed so as to form an angle of about 45 degrees with the traveling direction of the vehicle. M microphones 4 are arranged on the arrays 3a and 3b. The outputs of the M microphones are input to the signal processing device 6 together with the output of the speed detection sensor 5 via the connection cable 10.

The procedure of processing in the signal processing device 6 is shown below. Time t of the sound source S on the side of the vehicle captured by the j-th microphone 4j of the M microphones
The waveform Pj (t) of the radiated sound at is expressed by the equation 1.

[0021]

[Equation 1]

Here, S (t) is the strength of the sound source at time t, and Rj (t) is the j-th microphone 4 from the sound source S.
The distance to j, A means the output voltage sensitivity of the microphone, and c means the speed of sound. Rj (t) / c is the time delay until the sound emitted from the sound source S reaches the j-th microphone 4j. The coordinates of the sound source S at t = 0 are (Xs, Y
s, 0), and the coordinate system is set so that the moving direction is V in the X direction, and the coordinates of the microphone 4j at this time are (Xj, Y).
j, Zj), Rj (t) can be calculated by Equation 2.

[0023]

[Equation 2]

Here, the delay time calculation device 61 in the signal processing device 6 uses the sound source speed V detected by the speed detection sensor 5.
Rj (t) is calculated by the equation 2 from the data of M, and the output Pj (t) of the M microphones is delayed by the signal delay circuit 62 from the sound source S to each microphone R.
Only j (t) / c is corrected to Pj (t + Rj (t) / c). When the corrected microphone outputs are added by the adder 63, the waveform of the sound source S can be calculated as shown in Equation 3.

[0025]

(Equation 3)

Here, Wj is a window function for each microphone output for improving the directional characteristics of the array, and is multiplied by each microphone output in the signal delay circuit 62 or the adder 63. For this value, for M microphones arranged at equal intervals on a straight line, for example, the rectangular window shown in Formula 4 or the Hanning window shown in Formula 5 is used.

[0027]

[Equation 4]

[0028]

(Equation 5)

Further, the frequency analysis of the sound source by the sound pressure waveform S (t) is performed by the frequency analysis device 64. The spectrum Sp (f) at the frequency f is measured N times, and the decibel arithmetic averaging device 65 performs the averaging process shown in Formula 6 to obtain the decibel arithmetic mean value Spa (f).

[0030]

(Equation 6)

Here, S0 is a reference value when the decibel value is calculated.

FIG. 2 shows an example of a flowchart of signal processing in the signal processing device 6 of the above embodiment. In FIG. 2, the sound pressure Pj (t) obtained from the output of the j-th microphone that is first read into the buffer is used to perform the processing of Expression 3. In FIG. 2, when additional data that does not exist in the buffer is needed, additional data is newly read.

Frequency spectrum Sp obtained by FFT
(F) is immediately 20 log (| Sp (f) | / So)
Is converted to a decibel value. From this, the averaging process based on Equation 6 is performed to obtain the desired Sp (f).

Since the averaging means that the sound source moves with the progress of time, the averaged frequency spectra are obtained at different sound source positions. Therefore, the sound source 2
The dimensional separation performance is different for each measured spectrum. An example of the sound source distribution calculated value is shown in FIGS. In FIGS. 3 and 4, 15 microphones are attached to the pair of microphone arrays 3a and 3b at intervals of 27 cm, and a point sound source 1a passing through a position about 1 m higher than the center of the microphone array about 5 m away from the microphone array is shown. At some point, using the equations 1 to 4, the point sound source 1a as the center 6
The sound source distribution calculation value within the frame 8 in the range of m × 6 m is shown. FIG. 3 shows the case where the sound source is in front of the microphone array.
Is the case where the sound source is located about 10 m before the microphone array.

In the sound source distribution calculation, since S (t) does not become 0 even when the processing of the expression 3 is performed at a position other than the original sound source position 1a, the expression 6 is used in FIGS. 3 and 4.
The equal sound source intensity line connecting the positions where the decibel value is equal when the spectrum at the position is 0 dB is displayed. The line labeled -3 dB around the sound source 1a is generally called the sound source resolution. From the figure, it can be seen that the sound source resolution varies greatly depending on the position of the sound source.

FIG. 5 shows that the sound source distribution is calculated five times when the sound source is located in front of the microphone array at about 10 m, 5 m, at the sound source position, and at 5 m, 10 m after passing, respectively, and the obtained sound source distribution is shown. An example of the arithmetic mean of decibels given by Equation 6 is shown. In FIG. 5, the region 7 outside the line of −15 dB is lower than the value at the true sound source position 1a by −15 dB or more. FIG. 6 shows the result of decibel averaging by Equation 7 the sound source distribution obtained by Equation 3 that is conventionally performed. As is apparent from a comparison between FIG. 5 and FIG. 6, the weighting of a position having a relatively low root mean square value of the sound source distribution is higher when the arithmetic mean of the decibel values is performed, and therefore, in the present embodiment. The sound source resolution is further improved by using the decibel arithmetic mean.

[0037]

(Equation 7)

The measurement results shown in FIGS. 3, 4, 5 and 6 are examples at 4000 Hz when 15 microphones are attached to each of the microphone arrays 3a and 3b of FIG. 1 at 27 cm intervals. And the microphone distance d is about 3 times the wavelength λ of sound of about 8.5 cm.
In the conventional microphone array, as described in pp. 916 to 922 of Vol. 44, No. 12 (1988) of the Acoustical Society of Japan, the distance d between the individual microphones on the microphone array is 1 of the wavelength λ of the sound wave. It has been done below / 2. This is based on the sampling theorem, which shows the limit that the sound waves of the wavelength λ having different incident angles can be distinguished by the microphone of the interval d. In this embodiment, as shown in FIG. 7, the sound source 1b and the microphones 4a, 4b, 4 are
Since the distances Ra, Rb, Rc and Rd of the microphones of c and 4d are calculated by the equation 3, if all the microphones are not on the same straight line, the microphone array as a whole is focused on one point of the sound source 1b three-dimensionally. The microphone spacing d can be set to 1 / 2λ or more, exceeding the limit of the conventional sampling theorem.

FIG. 8 shows an example of the microphone array discussed on pages 167 to 170 and 1391 to 1396 of the conventional proceedings of inter noise 88 (1988). In this conventional device, they are arranged in a direction parallel and orthogonal to the moving direction of the moving sound source. When the processing corresponding to FIG. 5 is performed by the processing method used in the embodiment shown in FIG. 1 using the microphone array arranged as shown in FIG. 8, the result shown in FIG. 9 is obtained. As is clear from the comparison between FIG. 9 and FIG. 5, it can be seen that the sound source resolution of FIG. 5 is higher than the sound source resolution shown in FIG. 9, and the effect of this embodiment can be seen.

FIG. 10 shows another embodiment of the present invention. FIG.
The embodiment shown in FIG. 0 is an example in which a microphone array arranged in an X shape is used to search for a sound source of noise emitted from an automobile moving in front of the microphone array. In FIG. 10, the ceiling surface 1c of the automobile cannot be directly seen through the microphones below the microphone array. For this reason,
Ceiling surface 1c of the microphones on the microphone array
It is also possible to analyze the sound source distribution using only some microphone arrays that can see the sound source. In the conventional horizontal and vertical arrays shown in FIG. 8, the horizontal resolution of the sound source disappears at a position where the microphones on the horizontal array 3d cannot see through. However, according to the present embodiment, 3e of the microphone arrays are used. Since there is horizontal and vertical resolution, the horizontal resolution will not be lost. It is also possible to detect the moving speed of the moving sound source from the microphone 4e in the microphone array or the duration of the sound generated by the moving sound source captured by the microphone provided near the moving sound source.

FIG. 11 shows another embodiment of the present invention. In FIG. 11, the microphones are randomly arranged three-dimensionally. The processing can be performed by recording the outputs from the plurality of microphones in the two recording devices 9a and 9b, and then connecting the recording devices 9a and 9b to the signal processing device 6 and reproducing the recorded data. However, in this case,
The window function Wj shown in Expression 3 uses the rectangular window of Expression 4.
At this time, by recording the output of the same microphone 4f in both the recording devices 9a and 9b, it is possible to synchronize the recording devices with each other when reproducing the recorded data.

Further, when three or more recording devices are used, similarly, if at least one microphone output of the signals of the microphone array recorded in each recording device is recorded in another recording device. Good. Further, even if the moving sound source does not move linearly, it can be processed by considering the moving speed of the sound source at each time in the calculation of Formula 2. Also, Journal of Acoustical Society of Japan, Vol. 44, No. 12 (198
8), the source S is separated by the product of Sa (t) and Sb (t) obtained by applying the equation 3 to the pair of microphone arrays 3a and 3b of FIG. 1, respectively. It is also possible to do so.

[0043]

According to the present invention, since the sound source distribution on the moving sound source by the microphone array can be accurately measured, when the railway vehicle or the automobile is actually traveling,
Since the noise generation position can be found, the above noise can be efficiently reduced, and the wind noise generation source can be searched accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a moving sound source measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart of signal processing.

FIG. 3 is a diagram showing a sound source distribution calculation value when a sound source is in front of a microphone array.

FIG. 4 is a diagram showing calculated values of a sound source distribution when the sound source is displaced 10 m from the front of the microphone array.

FIG. 5 is a diagram showing an example of a decibel arithmetic average of a sound source distribution according to an embodiment of the present invention.

FIG. 6 is a diagram showing an example in which conventional signal processing is performed in an embodiment of the present invention.

FIG. 7 is a perspective view showing an arrangement example of microphones according to an embodiment of the present invention.

FIG. 8 is a perspective view showing a conventional sound source measuring device.

FIG. 9 is a diagram showing an example of measurement by a conventional sound source measuring device.

FIG. 10 is a perspective view showing a moving sound source measuring apparatus according to another embodiment of the present invention.

FIG. 11 is a configuration diagram of a moving sound source measuring apparatus according to another embodiment of the present invention.

[Explanation of symbols]

1 ... Moving sound source, 3 ... Microphone array, 4 ... Microphone, 6 ... Signal processing device.

Claims (10)

(57) [Claims] 1. A moving sound source measuring apparatus for measuring a sound source distribution on an object that moves relative to these microphones, the plurality of microphones being arranged in an array. A pair of microphone arrays are crossed with each other, and each of the pair of microphone arrays is arranged in a direction that is not orthogonal to the moving direction of the sound source. A delay time calculation device that corrects only the arrival time of a sound wave to a microphone, an addition device that superimposes the corrected signals, a frequency analysis device that performs a frequency analysis of the superposed signals, and a spectrum of the frequency analyzed spectrum. A moving sound source measuring device comprising a decibel arithmetic averaging device for averaging. 2. A moving sound source measuring device for measuring a sound source distribution on an object that moves relative to these microphones, the plurality of microphones being arranged in an array, and A pair of microphone arrays are crossed with each other, and each of the pair of microphone arrays is arranged in a direction that is not orthogonal to the moving direction of the sound source. A delay time calculation device that corrects the acoustic signal detected by the microphone by the arrival time of the sound wave from the moving sound source to each microphone,
An addition device for superposing the corrected signals, a frequency analysis device for performing frequency analysis of the superposed signals, and a decibel arithmetic averaging device for averaging the frequency-analyzed spectra. Measuring device for moving sound source. 3. A moving sound source measuring apparatus for measuring a sound source distribution on an object that moves relative to these microphones by using a plurality of microphones, the direction being intersecting and not orthogonal to the moving direction of the sound source. Using a plurality of microphones arranged in the microphone, the acoustic signals detected by the microphones are superposed by staggering the arrival time of sound waves from the moving sound source to each microphone, thereby increasing the directivity of the microphones and A moving sound source measuring method characterized by measuring a sound source distribution a plurality of times and averaging the measured sound source distributions. 4. The mobile sound source according to claim 1, wherein an interval between the microphones is set to be longer than ½ of a wavelength length at a highest frequency of sound emitted from the mobile sound source. Measuring device. 5. The moving sound source according to claim 1, 2 or 4, wherein the pair of microphone arrays are set to be orthogonal to each other and to form an angle of about 45 degrees with respect to the moving direction of the sound source. Measuring device. 6. The moving sound source measuring apparatus according to claim 1, 2 or 4, wherein the pair of microphone arrays intersect each other in a V shape. 7. The moving sound source according to claim 3, wherein a plurality of measurement results of the sound source distribution represent the strength of the sound source in decibels, and an average of the measurement results is calculated by an arithmetic mean of the decibel values. Measuring method. 8. The speed of a moving sound source moving relative to the microphone array is determined by a time interval between sounds emitted from two different sound sources on the moving sound source, which are being output from a microphone near the moving sound source. 7. The method for measuring a moving sound source according to 7. 9. The outputs of a plurality of microphones on the microphone array are recorded on a plurality of recording devices capable of recording and reproducing at the same time, and the outputs of at least one microphone on each recording device are simultaneously recorded on other recording devices. The method for measuring a moving sound source according to claim 3, 7, or 8. 10. When the sound source of the moving sound source cannot be seen from all the microphones on the microphone array, the moving sound source is measured only from the output of the microphones on the microphone array that can see the sound source. The moving sound source measuring method according to claim 3, 7, 8 or 9.