JP2000266832A - Method and device for measuring sound source direction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a sound source direction without being restricted by the interval of a sensor by receiving a sound wave from the sound source by a plurality of sound wave sensors being arranged at intervals, and by calculating the angle of the arrival direction of the sound wave from a phase difference change rate to the frequency between extracted reception signals, an interval, and the speed of sound. SOLUTION: In sensors 11 and 12 being installed at intervals, a sound wave from a sound source is received, and the reception signal is converted to a frequency region signal by a two-channel Fast Fourier transform part 13. At a phase information analysis part 14, the maximum phase change rate ϕ of a frequency band with a high correlation of the converted frequency region signal is extracted. Then, according to θ=cos-1(cϕ/2πL) (c and L are the speed of sound under water and the interval of the sensor, respectively), an angle θof a sound source direction is calculated, thus obtaining the sound source direction without the restriction of wavelength by the interval of the sensor when a bandwidth where the phase change rate can be detected exists in the sound source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound source direction measuring method and apparatus, and more particularly, to a sound source direction measuring method and apparatus capable of measuring the arrival direction of a sound wave having a wide frequency band with high reliability.

[0002]

2. Description of the Related Art A sound source direction measuring device for analyzing an incoming sound wave and measuring a sound source direction is, for example, capable of measuring a sound source direction of an underwater sound arriving at two or three points distant from each other by triangulation. The method is widely applied to sonar and the like for specifying the position of a sound source using the method.
Japanese Patent Publication No. 81 proposes a target position detection device and the like that detects the position, the moving direction, and the speed of a sound source by also analyzing the Doppler effect of underwater sound coming from a moving sound source.

FIG. 2 is a conceptual diagram for explaining the basic principle of such a conventional sound source direction measuring apparatus, in which an incoming sound wave is measured using two sensors 11 and 12 arranged at an interval L. . If the sound source is far enough compared to the interval L, the incoming sound wave can be regarded as a plane wave. Therefore, when the sound speed is c by measuring the reception time difference μ of the sound wave having the same phase, when the sound speed is c, The angle θ of the sound source direction with respect to the line segment connecting 11 and 12 can be obtained. θ = cos ^-1 (μc / L) (1) Further, for example, the sensor 11 is installed by mounting the sensor 13 in a direction perpendicular to a line connecting the sensors 11 and 12 with the sensor 11.
By determining the angle of the sound source direction with respect to the line segment connecting the sensor and the sensor 13, the sound source direction with respect to the sensor plane can be specified. In addition, by specifying the sound source direction in the same way at two sufficiently separated points, the sound source position can be calculated from the intersection of the two-directional lines.

[0004]

However, such a conventional sound source direction measuring apparatus has the following problems. That is, since the reception time difference μ of the in-phase sound wave is measured, when the sound wavelength is λ, λ
Only frequency components of / 2> L (sensor interval) can be used for measurement. For this reason, for example, in order to avoid undersea noise having many low-frequency components and to measure in a high-frequency region, the sensor interval L cannot be made large, and there has been a problem that the measurement accuracy is limited.

[0005] In addition, the reception time difference is measured using the fundamental wave of the normally arriving sound wave due to the above-mentioned restrictions.
The following sound sources cannot be measured, and even if the fundamental wavelength is 2L or more, there is a problem that the measurable sound source frequency is restricted such that correct measurement cannot be performed when there is a lot of environmental noise in the frequency region.

Furthermore, even when the frequency of the sound source is in the measurable region, sufficient confidence may not be obtained because the reception time difference μ is measured using one fundamental wave of the normally arriving sound. In addition, if a plurality of frequency components are to be used to increase the certainty factor, the above-mentioned restrictions are imposed, and a complicated operation is required.

The present invention solves such a problem and is not restricted by the distance between the sensors. Therefore, it is possible to set a sensor interval according to a desired accuracy, and it is possible to set a sensor interval according to a sound source and a measurement environment. Provided is a sound source direction measurement method and apparatus that can easily analyze an incoming wave in an optimal frequency band to selectively measure a sound source direction and obtain a highly confident measurement result by utilizing a broadband incoming wave. The purpose is to:

[0008]

In order to achieve the above object, a sound source direction measuring method according to the present invention comprises the steps of: receiving a sound wave coming from a certain sound source by a plurality of sound wave sensors arranged at intervals. And, phase information extraction step of extracting a phase difference change rate with respect to the frequency between the received signals of the sound waves received by the plurality of sound wave sensors, and from the phase difference change rate and the interval and sound speed, the direction of the interval and the Calculating the angle between the arrival directions of the sound waves.

The phase information extracting step includes an FFT (Fast Fourier Transform) processing step of converting each of the received signals into a frequency domain signal, a step of calculating a degree of correlation between the frequency domain signals, Calculating a phase difference between the area signals, and extracting the phase difference change rate from a change rate of the frequency difference of the phase difference with respect to the frequency in a frequency band having a degree of correlation equal to or more than a predetermined threshold value. It is characterized by.

Still further, a sound source direction measuring apparatus according to the present invention is provided with two sound wave sensors installed at intervals to convert an incoming sound wave into a time domain electric signal, and converts each of the time domain electric signals into a frequency domain signal. A two-channel FFT processing unit for converting the frequency domain signal into a frequency band having a correlation degree equal to or higher than a predetermined threshold, a change rate of the phase difference with respect to the frequency, the interval and the sound speed, the direction of the interval, and the A phase information analyzer for calculating an angle between the arrival directions.

Therefore, according to the sound source direction measuring method and measuring apparatus of the present invention, the sensor interval is not restricted by the reception wavelength, so that the sensor interval can be set according to the desired accuracy. Also, by referring to the degree of correlation,
An incoming wave in an optimal frequency band can be easily selected according to a sound source and a measurement environment, and a highly reliable measurement result can be obtained by using an incoming wave in a wide band.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, both sensors 11, 12 are used.
By extracting the change in frequency (frequency derivative) of the phase difference φ of the arriving sound wave caused by the reception time difference μ of
The reception time difference μ is obtained, and the sound source direction is obtained by the above equation (1). With reference to FIG.
The phase difference φ of a certain frequency component of the sound wave arriving at 2 is represented by the following equation when the frequency is f. φ = 2πf · μ (2) Therefore, from equation (1), φ = 2πf · (Lcos θ / c) (3) is obtained. Here, assuming that the ratio between the inter-sensor α and the wavelength λ of the sound source frequency f is r, the relationship can be expressed by the following equation. λ = c / fc: Underwater sound velocity (m / s) r = λ / α FIG. 3 shows the ratio r between the sensor interval L (m) and the wavelength λ of the sound source frequency f, r = 5.5E ^{−4 to} 3 , Sound source direction angle θ = 0 °
FIG. 3 is a graph showing the change of the phase difference φ (degree) according to the equation (3) in the range of 180 ° (10 ° steps). As shown in FIG. By calculating the derivative φ ′ = dφ / df, 10
The sound source direction can be measured practically sufficiently within the range of ° to 170 °.

That is, if the rate of change φ ′ of the phase difference with respect to the frequency can be extracted from the sensor reception signal, the angle θ in the direction of the sound source can be calculated by the following equation. θ = cos ⁻¹ (cφ ′ / 2πL) (4) The phase difference change rate is obtained, for example, by performing a two-channel FFT (fast Fourier transform) process on the reception signals of both sensors 11 and 12 and obtaining phase information of the cross spectrum. Can be easily obtained together with the degree of correlation between the two received signals.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of a sound source direction measuring apparatus according to the present invention, in which two sensors 11 and 12 arranged at an interval and the two sensors 11 and 12 are arranged.
A two-channel FFT unit 13 for converting received signals of the two sensors 11 and 12 into frequency domain signals, and a maximum likelihood phase change rate φ ′ of the frequency domain signals in a frequency band having a high degree of correlation.
And a phase information analyzer 14 for calculating the angle θ of the sound source direction according to the equation (4).

FIGS. 5 and 6 show examples of actual measurement data for explaining the operation of the present embodiment. Measurement was performed in the environment shown in FIG. Referring to FIG. 4, the actual measurement is performed by suspending a rigid body having sensors 11 and 12 installed at an interval L = αm at a water depth of about 10α (m) with respect to the sensor interval α (m) and about 6α (m) below the actual sea level. And the transmitter is suspended at each of the sound source positions 1 to 7 so that r ≒ 1
３3 random noises were transmitted. FIGS. 5 and 6 show examples of the phase difference and the correlation obtained by converting the reception signals from the sound source positions 2 and 6 into frequency domain signals by the two-channel FFT unit 13 and analyzing by the phase information analysis unit 14, respectively. It is.

For example, when the frequency change of the phase difference shown in FIG. 5 is seen, a periodic variation which is considered to be due to the influence of sea surface reflection is seen, but a sufficient correlation can be obtained by referring to the degree of correlation.
By estimating the maximum likelihood value by, for example, the least squares method from the phase change rates of the bands of # 1 to # 3, it can be seen that a phase change rate with sufficiently high certainty can be obtained. The same can be said for FIG. 6 affected by seafloor reflection.

In this way, the phase information analyzer 14 selects a frequency band in which the degree of correlation is equal to or greater than a predetermined threshold, obtains the maximum likelihood value φ 'of the phase change rate, and obtains the sound source according to the equation (3). The angle θ formed by the line segment connecting the direction and the sensor is calculated and output.

The arrows attached to the sound source positions 1 to 7 in FIG.
The difference between the sound source direction measured in this way and the actual sound source direction is schematically shown. At the sound source positions 1, 2, and 7 where the sound source incident angle becomes an acute angle, slight errors are seen due to the influence of the sea surface and the sea floor, and the approximation of a spherical wave from a short-range sound source by a plane wave. In No. 6, a sufficiently accurate angle θ of the direction of the sound source could be obtained.

[0019]

As described above, according to the sound source measuring method and apparatus according to the present invention, if the sound source has a bandwidth capable of detecting the rate of phase change, the sound source is not restricted by the wavelength of the sensor interval L. The direction can be determined. Generally, it is rare that a measurement target such as a sonar is close to a pure sound source, so that a sound source measuring device having higher applicability than a conventional sound source measuring device can be obtained.

Also, for a sound source having a spike characteristic close to a pure tone such as a mechanical noise, the phase change rate can be obtained by analyzing a plurality of spikes such as harmonics, so that the application is also highly applicable. A sound source measuring device can be obtained.

Further, as shown in the equation (3), the sensor interval L
Can increase the resolution of the phase difference φ, so that a more accurate measurement can be performed as compared with the conventional sound source measuring device.

Furthermore, by referring to the degree of correlation, the maximum likelihood phase change rate can be obtained from the phase difference information in a significant wide band, excluding a frequency band with much noise, so that highly accurate measurement is possible. Becomes

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a sound source direction measuring device according to the present invention.

FIG. 2 is a conceptual diagram illustrating the principle of sound source direction measurement.

FIG. 3 is a graph showing a change in a phase difference depending on a frequency.

FIG. 4 is a schematic diagram illustrating an example of actual measurement by the sound source direction measuring device in FIG. 1;

FIG. 5 is a graph showing an example of actual measurement of a phase difference and a degree of correlation of a received signal from a sound source position 2 in FIG. 4;

6 is a graph showing an example of actual measurement of a phase difference and a correlation degree of a received signal from a sound source position 6 in FIG.

[Explanation of symbols]

 1-7 Sound source position 11, 12 Sensor 14 2-channel FFT 15 Phase information analyzer

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] November 26, 1999 (1999.11.
26)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirozo Ishimae 781 Shin-Yoshida-cho, Kohoku-ku, Yokohama-shi, Kanagawa Japan FRC Terminator FJ (reference) 5J083 AA05 AB12 AC17 AC32 AD18 AE07 AF01 BE07 BE39 BE43 CA07

Claims (3)

[Claims] 1. A step of receiving sound waves arriving from a certain sound source by a plurality of sound sensors arranged at intervals, and a phase difference change with respect to a frequency between reception signals of the sound waves received by the plurality of sound sensors. A phase information extracting step of extracting a rate; and a step of calculating an angle between the direction of the interval and the direction of arrival of the sound wave from the phase difference change rate and the interval and the speed of sound. Measuring method. 2. The phase information extracting step comprises: converting each of the received signals into a frequency domain signal.
FT (Fast Fourier Transform) processing; calculating a degree of correlation between the frequency domain signals; calculating a phase difference between the frequency domain signals; Extracting the phase difference change rate from the change rate of the band with respect to the frequency of the phase difference with respect to the frequency. 3. Two sound wave sensors installed at intervals and converting an incoming sound wave into a time domain electric signal; a two-channel FFT processing unit converting each of the time domain electric signals into a frequency domain signal; Phase information analysis for calculating the angle between the direction of the interval and the direction of arrival of the sound wave from the rate of change of the phase difference with respect to the frequency and the interval and the speed of sound in the frequency band in which the degree of correlation of the frequency domain signal is equal to or greater than a predetermined threshold And a sound source direction measuring device.