JP2899267B1 - Closed space point sound source measurement device - Google Patents

Abstract

An apparatus for accurately measuring the position and intensity of a point sound source generated somewhere in a closed space, such as a measuring unit of a circulating water tank, is provided. SOLUTION: n hydrophones 30, an A / D converter 40, a DSP 50, a signal processing circuit 60, and a storage table 7 are provided.
Using 0 and the arithmetic circuit 80, a monitor sound is generated for each coordinate position by the monitor point sound source having the output intensity b, and the sum A of the amplitude values at each coordinate position and the sound field correction value C are stored. When a point sound source is present in the closed space, the operation of sequentially dividing the discrete Fourier transform A ″ having averaged amplitude values by the sound field correction value C is repeated, and the amplitude value (absolute value) of the sum S (complex number) after the division is obtained. ) Specify the coordinate position where S 'is the maximum as the position of the point sound source, and specify its intensity by b · S' / A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a closed space for measuring the three-dimensional position (also referred to as a sound field) and its level (also referred to as intensity) of a point sound source generated in a closed space such as a measuring section of a circulating water tank. The present invention relates to a point sound source measuring device.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the position and level of a point sound source in a closed space in general, which is used in a circulating water tank that simulates noise generated during navigation of a ship using a scale model of the ship. Will be described as an example. FIG. 5 is a diagram showing an example of this type of circulating water tank. In the figure, 1 is a circulating pipe, 2 is a water supply device, and 3 is a measuring unit. The water supply device 2 constantly absorbs water from the water absorption unit 13, applies water pressure, and sends water at a predetermined pressure from the water supply unit 10, and the water circulates in the circulation pipe 1. The water supplied from the water supply device 2 enters the rectification unit 11 whose diameter is expanded via the water supply unit 10, the flow of the water is adjusted by the rectification unit 11, and reaches the measurement unit 3 through the elbow unit 12. . The measuring unit 3 is provided with various measuring devices. For example, an object to be measured such as a scale model of a ship is installed in the water flow of the measuring unit 3 to measure noise generated during navigation of the ship. A simulation is performed.

[0003] Various methods have been attempted for measuring the above-mentioned noise in such a circulating water tank. However, the measurement space is closed, and the sound source is in the vicinity of a sensor (hydrophone). It is difficult to measure accurately.
For example, as shown in FIG. 6, the configuration is such that hydrophones are arranged on the F surface (upper surface) and the G surface (one side surface) of the closed space forming the measuring unit 3, and each surface or two surfaces are combined. A correction is made so that there is no spatial delay difference between the outputs of the hydrophones, and a directional beam is formed by the addition, and the directional beam is moved at each coordinate position in the space, thereby to somewhere in the closed space. The three-dimensional position and intensity of the point sound source generated by the above can be measured.

[0004]

However, the sound generated at a short distance in a closed space cannot be accurately identified because the intensity and phase difference of each sound are changed for each hydrophone due to the reflection on the side surface. . For example, as shown in FIG. 7, the output of the hydrophone h2 is received by combining the sound generated at the point P directly to the hydrophone h2 and the sound reflected by the F surface and reaching the hydrophone h2. Phenomenon, making accurate measurement difficult.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a closed space point sound source measuring apparatus capable of accurately measuring the position and level of a point sound source near a closed space.

A closed space point sound source measuring apparatus according to the present invention comprises:
N number of hydrophones are arranged in suitable between isolation on one surface or surfaces of the closed space, in the closed space point source measuring device for measuring the three-dimensional position and intensity of the point sound source generated somewhere in the closed space A sound wave (frequency f) received by each hydrophone arranged on one or more surfaces of the closed space is converted to a frequency F
(Frequency equal to or more than twice as high as frequency f) and converts them into digital data by n A / D converters, and fast Fourier transforms the outputs from the n A / D converters into n And a digital signal processor that obtains a discrete Fourier transform of the following formula, and extracts a discrete Fourier transform (vector) of a frequency component equal to the frequency f in each of the n discrete Fourier transforms, and obtains information on the sum of amplitude values (absolute values). A signal processing circuit that obtains the sound field correction value C (vector) of each of the n hydrophones by calculating the unit vector, and the coordinates of the closed space using the monitor point sound source whose output intensity is b. A monitor sound is generated for each position, and the sum A of the amplitude values (absolute values) at each coordinate position and the sound field correction value C are calculated for each coordinate position. A storage table that is measured for each position and stored in correspondence with each coordinate position, an arithmetic circuit, and when a point sound source exists in this closed space, the n hydrophones and the A / D converter Using the digital signal processor, the signal processing circuit, and the arithmetic circuit,
A discrete Fourier transform of a frequency component equal to the frequency of the point sound source is extracted for each of the n hydrophones, amplitude values (vectors) of the extracted discrete Fourier transforms are averaged, and the averaged discrete Fourier transform A ″ is averaged. repeating the calculation of said sequentially dividing the sound field correction value C for each coordinate position, the n hydrophones the vector after dividing every each coordinate position
, And sum of the amplitudes of the vector sum S
Means for measuring the three-dimensional position of the point sound source by obtaining the coordinate position of the closed space that gives the maximum value; and the amplitude (absolute value) of the maximum value of the vector sum S obtained for each coordinate position of the closed space. ) S ′ and the sum A of the amplitude values (absolute values)
And means for measuring the intensity of the point sound source by b · S ′ / A using the intensity b.

Therefore, reflected waves from the side are synthesized,
Accurate position measurement and intensity measurement are possible even when a phenomenon peculiar to the closed space short-range sound field occurs. In addition, since a discrete Fourier transform is obtained by performing a fast Fourier transform using a digital signal processor, comparison of information on each phase state and comparison of the sum of amplitudes can be performed at high speed and accurately.

[0008] Further, the n hydrophones, which are appropriately spaced apart from each other on one or more surfaces of the closed space, are arranged irregularly. When arranging a limited number of hydrophones in a relatively large space, the distance between each of the n hydrophones is set to be more than 波長 wavelength of the frequency to be measured, and the output of the A phenomenon occurs in which the coordinates are almost aligned at coordinate positions other than the focal position. Therefore, by arranging the hydrophones irregularly, this phenomenon is mitigated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic principle of point sound source measurement according to the present invention will be described. The basic principle of the present invention is that, for example, as shown in FIG. 1, in a configuration in which n hydrophones are installed on one side of a measurement space 10 (measurement unit 3 in the case of a circulating water tank), first each coordinate of the measurement space The monitor sound of the point sound source is generated at all the positions, and the state of the amplitude and phase of the sound wave received by each of the n hydrophones is monitored for each coordinate position and stored in the storage table. deep. In the measurement of the noise source, when noise is generated, the position of the noise source is specified based on which of the stored phase states of the waveforms received by each hydrophone matches. In other words, the sound wave received by each hydrophone is, even if the reflected wave from the closed space side is synthesized and the phase changes, if the sound is generated from the same sound field, the sound wave received by each hydrophone is Each frequency component is relative
The sound source position is specified by using the principle that the phase state is the same. When the sound source position can be specified, the noise source strength can be specified by comparison with the monitor sound intensity stored at the sound source position.

Next, an embodiment of the present invention will be described.
FIG. 3 is a block diagram showing an embodiment of the apparatus configuration of the present invention.
40 is an A / D converter, 50 is a digital signal processor (DSP), 60 is a signal processing circuit, 70 is a storage table, and 80 is an arithmetic circuit.

For example, as shown in FIG.
Install hydrophones (1-n) on the side, X, Y, Z
Coordinate points (x _i , y _J , z _K on the three-dimensional coordinates of
_i = 1,2 ... i, _J = 1,2 ... j, _K = 1,2 ... k) and put monitor sound sources (pure sound: sin wave point sound source) Rather, the phase difference and the amplitude value of the sound wave received by each hydrophone 30 are monitored. For example, as shown in FIG. 2, a monitor sound source having a frequency f (selecting a frequency close to the frequency of the actually generated noise) and an intensity b is arranged at a coordinate point P _ijk , and from n hydrophones h1 to hn, Are received by the A / D converter 40 at the same time at a constant frequency F
Sampling is performed with a clock signal (frequency twice or more than the frequency of the monitor sound), and A / D conversion is performed. As a result, n sets of data consisting of successive sample values of an appropriate length are obtained for each hydrophone.

Next, the n sets of data are respectively stored in the DSP
(Digital Signal Processor) FFT using 50
(Fast Fourier transform). As a result, a discrete Fourier transform of each frequency component for each of the n sets of data is obtained. Then, the signal processing circuit 60 pays attention only to the discrete Fourier transform of the frequency component equal to the frequency f of the monitor sound source, obtains the sum A _{ijk of the} amplitude values,
The monitor sound intensity at the coordinate point P _ijk is set.

Also, it is equal to the frequency f of the monitor sound source.
Unit vector of discrete Fourier transform of frequency componentC _ijk
(H1) -C _ijk (Hn)And n hydrophos
And sound field correction values for the respective ones of h1 to hn. ThereforeC
_ijk (H1) -C _ijk (Hn)Is P_ijkDeparts from
Of the received sound at each of the hydrophones h1 to hn
It is a relative phase angle. Also, the sum A of the amplitude values (absolute values)
_ijkIs P_ijkFrom each monitor sound source
Assuming that the phase of the received signals of the
The sum of the received signal levels of the hydrophones h1 to hn
You. The above operation is performed for each coordinate point P_ijkRow for all of
Each coordinate point P_ijkA about_ijkWhenC
_ijk (H1) -C _ijk (Hn)And the respective coordinates
Recorded in the storage table 70 as reference data in association with the points.
Remember. In the above description, the monitor sound source
f, but due to the frequency difference,
Considering that the reflectivity of the
To obtain reference data for each frequency using
May be.

Next, the specification of the three-dimensional position and intensity of the noise generated in the measurement space will be described. When noises at frequencies f ′ whose three-dimensional positions and their intensities are unknown are received by the hydrophones h1 to hn, sampling is performed in the same manner as in the case of the above-described monitor, and N samples are obtained for each hydrophone. Obtain n sets of sample values. The n sets of sample values are similarly FFT-transformed to extract a discrete Fourier transform of a frequency component equal to the frequency f '. Then, an average (A ′ / n) _AVR of these amplitude values is obtained, and a discrete Fourier transform A ″ corrected so that the amplitude of each discrete Fourier transform becomes (A ′ / n) _AVR is calculated. As a result, a discrete Fourier transform corresponding to each of the hydrophones h1 to hn and having the same amplitude but different phase angles is obtained. Next, using the arithmetic circuit 80, the sound field correction values C _ijk (h1) to C _ijk (hn) of the reference data in which the discrete Fourier transform A ″ having the same amplitude is stored in correspondence with each coordinate point by the monitor are stored. When there is a noise source at that coordinate point, a discrete Fourier transform A '''' in which the relative phase difference is canceled out is obtained, and the received waveforms from all hydrophones have the same phase. When the amplitude value (absolute value) of the sum (complex number) of the Fourier transform A ′ ″ is obtained, the value becomes maximum when there is a noise source at the coordinate point.

[0015] Thus corrected discrete Fourier transform A '' of each coordinate point sound field correction value _{C ijk (h1)} ~C _ijk
(hn) are repeatedly performed, and the amplitude value (absolute value) S _{ijk of the} sum (complex number) thereof is repeated.
Field correction values C _ijk (h1) to C _ijk (h
If n) can be extracted, the coordinate point P _ijk corresponding to the extracted sound field correction value can be specified as the coordinate position of the noise source . The intensity of the noise source is b (the intensity of the monitor sound source)
_-It can be specified by S _ijk / A _ijk .

Next, the arrangement of the hydrophone in the present invention will be described. FIG. 4A is a diagram showing an arrangement of hydrophones used in the closed space point sound source measuring device according to the present invention. Since the present invention specifies the sound source position based on the phase state of the sound wave received by each hydrophone as described above, the sound wave received by each hydrophone has a relative position at a coordinate position other than the beam focal position. There must be a difference. However, for example, when hydrophones are arranged at equal intervals as shown in FIG. 4B, the relative phases of sound waves received by some hydrophones are uniform, although not as remarkable as the sound field measurement at a long distance. In some cases. In other words, when placing a limited number of hydrophones in a relatively large space, if the distance between each of the n hydrophones is spaced apart by 以上 wavelength or more of the frequency to be measured, the hydrophone output becomes A phenomenon occurs in which the coordinates are almost aligned at coordinate positions other than the beam focal position. Therefore, in order to minimize the number of hydrophones having the same relative phase at coordinate positions other than the beam focal position, the present invention arranges the hydrophones irregularly.

In the above-described embodiment, the case where the hydrophone is arranged on one surface of the closed space is described, but it goes without saying that the same operation can be performed even if it is arranged on a plurality of surfaces.

[0018]

As described above, the closed space point sound source apparatus of the present invention can accurately measure the three-dimensional position and intensity of a point sound source generated at a short distance in a closed space. A remarkable effect is obtained for noise measurement and the like.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a basic principle of the present invention.

FIG. 2 is a diagram for explaining a basic principle of the present invention.

FIG. 3 is a block diagram showing an embodiment of the device configuration of the present invention.

FIG. 4 is a diagram for explaining a hydrophone arrangement example in the present invention.

FIG. 5 is a diagram for explaining a circulating water tank.

FIG. 6 is a diagram for explaining an example of a conventional closed space point sound source measurement method.

FIG. 7 is a diagram for explaining a problem of a conventional method.

[Explanation of symbols]

 Reference Signs List 10 measurement space 30 hydrophone 40 A / D converter 50 digital signal processor (DSP) 60 signal processing circuit 70 storage table 80 operation circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Minehiro Katayama 781 Shinyoshida-cho, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside JR RC Toki Co., Ltd. (56) References JP-A-8-226989 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01H 3/00 G01M 10/00 G01S 11/14 G01S 7/534

Claims (2)

(57) [Claims] 1. A closed space for measuring a three-dimensional position and intensity of a point sound source generated somewhere in this closed space by arranging n hydrophones on one or more surfaces of the closed space at appropriate intervals. In the point sound source measuring device, a sound wave (frequency f) received by each hydrophone arranged on one surface or a plurality of surfaces of the closed space is sampled at a frequency F (frequency twice or more than the frequency f) to obtain digital data. N digital A / D converters for converting the outputs from the n A / D converters into fast discrete Fourier transforms to obtain n discrete Fourier transforms, respectively; In each of the Fourier transforms, a discrete Fourier transform (vector) of a frequency component equal to the frequency f is extracted, and information on the sum of the amplitude values (absolute values) is obtained. A signal processing circuit for obtaining a sound field correction value C (vector) for each of the n hydrophones, and a monitor sound for each coordinate position in the closed space using a monitor point sound source whose output intensity is b. A storage table for generating and summing the sum A of the amplitude values (absolute values) and the sound field correction value C at each coordinate position for each coordinate position and storing them in correspondence with each coordinate position When a point sound source is present in the closed space, using the n hydrophones, the A / D converter, the digital signal processor, the signal processing circuit, and the arithmetic circuit, A discrete Fourier transform of a frequency component equal to the frequency of the point sound source is extracted for each of the n hydrophones, the amplitude values (vectors) of the extracted discrete Fourier transforms are averaged, and the averaged discrete Fourier transform is averaged. E converter A '' to repeat the operation in which the sequentially dividing the sound field correction value C for each coordinate position, the n hydrophones the vector after dividing every each coordinate position
, And sum of the amplitudes of the vector sum S
Means for measuring the three-dimensional position of the point sound source by obtaining the coordinate position of the closed space giving the maximum value; and the amplitude (absolute value) of the maximum value of the vector sum S obtained for each coordinate position of the closed space. Means for measuring the intensity of the point sound source by b · S ′ / A using S ′, the sum A of the amplitude values (absolute values), and the intensity b. Closed space point sound source measurement device. 2. The closed space point according to claim 1, wherein the n hydrophones which are appropriately spaced apart from each other on one or more surfaces of the closed space are irregularly arranged. Sound source measurement device.