JP3144442B2 - Sound source search method - 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 search system, and more particularly to an apparatus for searching for a position and a size of a noise source in a vehicle engine or the like.

[0002]

2. Description of the Related Art Conventionally, various methods for searching for a sound source have been proposed. As one of the methods, two scanning microphones are arranged at a fixed distance of about 6 to 50 mm before and after the sound source direction. By providing a microphone output while moving both scanning microphones in parallel in the near sound field of the sound source,
There is a method for obtaining the sound intensity of the sound source (“sound intensity method”).

In this method, a sound source is captured as acoustic energy flowing in a unit area per unit time, and the average value of the measured sound pressures of both scanning microphones is p (t), the particle velocity (a value proportional to the sound velocity, and per unit distance). U (t)
Then, by measuring the vector amount represented by the following equation (1) as a temporal average value of the product of the two, the sound source is located on the extension of both scanning microphones where the vector amount is the largest. Is what you do.

[0004]

(Equation 1)

Incidentally, the particle velocity u (t) represents a change in phase.

In such a sound source search method based on the sound intensity method, there is no correlation since the measurement results at each scanning microphone measurement point are independent of each other. Therefore, when the direction of the sound source is not parallel to the extension line direction of the microphone, There is a problem that a correct search cannot be performed.

A sound source search method based on the "acoustic holography method" has been studied before the above-mentioned sound intensity method, and one microphone that scans a measurement plane at a certain distance from the sound source and another microphone. A sound source is searched for by obtaining sound pressure intensities and phases of two microphone output signals with a reference microphone fixed at an appropriate position.

This will be described in more detail. In this method, the microphone M1 is moved to the measurement surface M as schematically shown in FIG.
Microphone output at each position can be obtained by scanning horizontally and vertically on F.
The following reproduction formula (2), which considers these microphone outputs and the sound pressure output of the reference microphone, and shows the back propagation formula of the sound wave propagation formula that is the basis for obtaining these microphone outputs,

[0009]

(Equation 2)

Thus, the complex volume velocity amplitude Q (x, y, 0) of one point R (x, y, 0) on the reproduction surface (sound source surface) RF reproduced from the microphone M1 is obtained. However, the above equation
R in (2) is a point P (x, y, zo) on the measurement surface MF.
) And a point R (x, y, 0) on the reproduction surface RF. In the expression (2), P (x, y, zo) indicates the complex sound pressure output from the Mac M1.

When the microphone M1 is scanned in the horizontal and vertical directions on the measurement surface MF, the complex volume velocity amplitude Q of one point R on the reproduction surface RF obtained by the output of each microphone position is obtained.
(X, y, 0) are all added, and the point R on the reproduction surface RF is set to all points on the reproduction surface RF, and the measurement surface M
By adding all the complex volume velocity amplitudes Q (x, y, 0) from F, a point having the largest amplitude Q will be searched for as a sound source.

FIG. 6 illustrates this point more specifically.
7 and FIG. 6A. First, in FIG.
When the reproduction point R on F is reproduced as the sound source S, the sound picked up at the microphone position M1-1 of the microphone M1 and the sound picked up at the microphone position M1-2 as shown in FIG. In the reconstructed ones, the propagation path of the sound wave and the back propagation path are equidistant and the phases are the same, and therefore, as shown in FIG. Is maximum when the reproduction point R on the reproduction surface RF is set to the sound source S, that is, at the position of the sound source S.

On the other hand, when the reproduction point R is reproduced at a position on the reproduction surface RF slightly deviated from the sound source S as shown in FIG. 6 (b), as shown in FIG. The length of the back propagation path during playback is longer and the microphone position M
In 1-2, the back propagation path at the time of reproduction is shorter than the propagation path.

Therefore, the phase of the sound reproduced at the microphone position M1-1 is different from the phase of the sound reproduced at the microphone position M1-2.
As shown in the figure, the combined vector (Q1
To Q3) are smaller than the combined vector shown in FIG.

By setting a large number of reproduction points R on the reproduction surface RF in this manner, when the reproduction point corresponds to the sound source position, the maximum synthesized vector is obtained as shown in FIG.
At other positions, a small synthesized vector is obtained as shown in FIG. 7B, so that the sound source search has been obtained in the former case.

[0016]

In the case of a sound source search using the above-described acoustic holography method, as shown in FIG. 7, the case shown in FIG. 7A and the case shown in FIG. There is a problem that the difference from the case shown is small and the detection accuracy of the sound source search is low.

Recently, a sound source search method based on the “short-range acoustic holography method” has been studied, which includes a mode in which a sound wave is linearly diffused from a sound source and a sound wave that propagates laterally from the sound source and attenuates at a short distance. Although the latter sound wave is also included in the search target by focusing on the fact that there is a mode in which the
When the sound source is a heating device (for example, a manifold of an engine), a microphone cannot be installed at a close distance, which is not suitable for measurement.

Further, as an application example of the sound intensity method, one reference microphone is used in addition to two scanning microphones, and the vibration mode of the sound wave propagating backward from the measurement surface and the radiated sound wave are used. Although there is a "proximity particle velocity method" for predicting directivity and sound pressure level, this method does not search for a sound source and cannot be used.

Therefore, an object of the present invention is to realize a sound source search method with higher detection accuracy by improving the above-described acoustic holography method.

[0020]

In order to achieve the above object, in a sound source search system according to the present invention, at least two scanning microphones arranged before and after a sound source and both scanning microphones are simultaneously moved in parallel. Means for inputting, at least one reference microphone, and sound pressure data of a sound source from each microphone, and assuming that sound pressure data of the first scanning microphone comes from the reproduction point direction, the second scanning microphone The sound pressure data at the position is converted, and the difference between the converted sound pressure data and the sound pressure data of the second scanning microphone is weighted to be synthesized with the sound pressure data of the second scanning microphone. The first
Calculation means for searching for the position of the sound source by performing the measurement on the entire measurement surface of the scanning microphone.

[0021]

FIGS. 1 and 2 are conceptual diagrams for explaining the sound source search system according to the present invention in an easy-to-understand manner. At least two scanning microphones M are provided on the surface to which the sound source S belongs, that is, on the reproduction surface.
1 and M2 are arranged in the front-rear direction.
1 and M2 are simultaneously translated, and the microphone output at each point is given to the arithmetic means.

The calculating means assumes that the complex sound pressure P2 output from the microphone M2 on the rear measurement surface MR comes from the direction of the reproduction surface RF, for example, and the complex sound pressure P2 at the position of the microphone M1 on the front measurement surface MF. 'Is converted, for example, according to the following equation (3).

[0023]

(Equation 3)

Note that r1 and r2 denote the distances from the microphones M1 and M2 to the reproduction point R on the reproduction surface RF, respectively, which are known distances Zo between the front measurement surface MF and the reproduction surface RF. And the distance ΔZ between the two measurement surfaces. Further, the relationship between the front measurement surface MF and the rear measurement surface MR may be reversed.

If the reproduction point R is not the sound source point, the complex sound pressure P2 'thus converted does not match the actual complex sound pressure P1 measured by the microphone M1.

Since the two sound pressures P1 and P2 'are complex numbers as shown in the following equation (3), the microphones M1 and M2 are obtained from the complex sound pressures P1 and P2' as shown in FIG. Is calculated by the following equation (4), for example.

[0027]

(Equation 4)

By applying the complex sound pressure P3 obtained in this manner to P (x, y, zo) in the above-mentioned reproduction equation (2), the same as in the conventional acoustic holography method, FIG. )
And (b) are obtained, and the reproduction point of the largest synthesized vector is the sound source point.

At this time, since the difference (P1−P2 ′) of the measurement data is weighted by multiplying the coefficient α (for example, 6 to 60) in the above equation (4), the complex sound pressure P1 When P2 'does not coincide with each other, the complex sound pressure P3 has a larger phase shift as shown in FIG. 7C, and the resultant vector is obtained by the conventional acoustic holography method shown in FIG. 7B. Since a value smaller than the combined vector is shown, the detection accuracy of the sound source point is improved. It is also conceivable that the coefficient α becomes a variable corresponding to the position of the reproduction point R, for example.

The first and second scanning microphones may correspond to either the front or rear measurement plane.

[0031]

FIG. 4 shows an embodiment of a sound source search system according to the present invention. In this embodiment, two scanning microphones M1 and M1 are used.
M2 and a fixed reference microphone M3 are used, and these scanning microphones M1 and M2 are arranged before and after the sound source S. The microphones traverse device TVS moves on the front measurement surface MF and the rear measurement surface MR, respectively. It is attached to support rods B1 and B2 so as to be moved horizontally. still,
Since the support bar B1 can move on the support bar B2, the scanning microphones M1 and M2 are eventually scanned in the horizontal and vertical directions on the front measurement surface MF and the rear measurement surface MR, respectively. .

Scanning microphones M1 and M2 and reference microphone M3
Are amplified by the amplifiers A1 to A3, converted into data by the A / D converters C1 to C3 in the front processor FP, and then converted to data by the fast Fourier transformers FFT1 to FFT in the front processor FP.
After being converted into the frequency domain by the FT3 (this is for obtaining the correlation), the holographic operation unit HC in the computer PC such as a personal computer or a workstation performs the above-described acoustic holographic operation and displays the display D such as a CRT or a plotter. Will be displayed.

The controller CNT for controlling the microphone traverse device TVS is also a computer PC
The movement speed of the microphone traverse device TVS controlled by the controller CNT is adjusted in advance to the speed at which the outputs of the microphones M1 to M3 are sampled. .

[0034]

As described above, according to the sound source search method according to the present invention, the sound of one of the scanning microphones is arranged by arranging at least two scanning microphones back and forth with respect to the sound source and simultaneously moving them in parallel. Assuming that the pressure data comes from the direction of the reproduction point, the difference is weighted by converting it into sound pressure data at the position of the other scanning microphone to obtain synthesized sound pressure data, and this is applied to the entire measurement surface. Since the configuration is such that the position of the sound source is searched for, the position of the sound source can be detected with high accuracy without being restricted by the size of the measurement surface or the distance between the measurement surface and the sound source surface.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an operation principle of a sound source search method according to the present invention.

FIG. 2 is a perspective view showing a sound source and a measurement surface of a sound source search system according to the present invention.

FIG. 3 is a vector diagram showing a complex sound pressure calculated by a sound source search method according to the present invention.

FIG. 4 is a diagram showing an embodiment of a sound source search method according to the present invention.

FIG. 5 is a diagram for explaining sound pressure reproduction by a conventional acoustic holography method.

FIG. 6 is a diagram showing a state in which a sound source is reproduced by a conventional acoustic holography method.

FIG. 7 is a diagram showing combined vectors on a reproduction surface obtained by the present invention and the conventional example.

[Explanation of symbols]

 M1, M2 Scanning microphone M3 Reference microphone S Sound source MF Front measurement plane MR Back measurement plane TVS Microphone traverse device FP Front processor PC Computer In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01H 9/00 G01H 3/10 G01V 1/00

Claims (1)

(57) [Claims] At least two scanning microphones arranged before and after a sound source, means for simultaneously moving both scanning microphones in parallel, at least one reference microphone, and sound pressure data of a sound source from each microphone. To convert the sound pressure data of the first scanning microphone into sound pressure data at the position of the second scanning microphone, assuming that the sound pressure data came from the reproduction point direction, and the converted sound pressure data and the second scanning The difference between the sound pressure data of the microphone and the sound pressure data of the second scanning microphone is weighted and combined with the sound pressure data of the second scanning microphone. A sound source search method, comprising: