JPH0722434B2 - Sound source direction detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial field In recent years, the development and use of robots having human functions have been increasing. The present invention relates to a sound source direction detecting device used for a device such as a robot that performs work on behalf of a human being, or a surveillance video camera.

2. Description of the Related Art FIG. 4 shows a block diagram of a sound source direction detecting device of a conventional example, and a conventional example will be described below with reference to this drawing.

Reference numeral 12 is a sound collector in which n microphones for collecting sound are arranged at equal intervals on a semicircle, and 13 is a direction detection circuit for obtaining the direction of the sound source. The sound pressures of the sounds picked up by the n microphones of the sound collector 12 differ depending on the sound source direction. That is, the sound picked up by the microphone closest to the sound source has the highest sound pressure. Based on this principle, the respective signals picked up by the n microphones of the sound pickup device 12 are input to the direction detection circuit 13, where the magnitudes of the signals are compared, and the maximum signal is picked up. The position of the microphone is detected, and the direction of the sound source is obtained from the position of this microphone. With the above configuration, the direction of the sound source can be obtained.

Problems to be Solved by the Invention However, in the conventional example shown in FIG. 4, in order to improve the direction discriminating ability, a great number of microphones are required to be provided on the semicircle, resulting in an increase in cost and a configuration scale. It had the drawback of becoming large.

In view of the above problems, the present invention provides a sound source direction detecting device that is low in cost, has a small configuration scale, and has high direction discriminating ability.

Means for Solving the Problems In order to achieve the above-mentioned object, the signals applied to the first and second microphones fixed between two points with a certain distance and the signals applied to the first and second microphones are First and second delay means for delaying, first and second band pass means for respectively receiving the output signals of the first and second delay means and passing only signals in a certain frequency band, and first First and second pulse generating means for outputting a positive or negative pulse signal when the output signal of the second band passing means exceeds a certain level, and first and second pulse generating means And a second pulse generating means for outputting a positive or negative pulse signal and an output signal of the third pulse generating means as an input, and the number of the signals in a certain time. Measuring means for measuring and outputting the value, and the delay time of the second delay means. Is varied with a predetermined width to detect the delay time of the second delay means which maximizes the output value from the measuring means, and the phase difference of the signals applied to the first and second microphones is detected from this delay time. And a phase difference detecting means for converting the sound source direction of the signal applied to the first and second microphones from the detected phase difference.

Operation According to the present invention having the above-described configuration, the signals picked up by the first and second microphones are delayed by a certain time by the first and second delay means. Then, the output signals of the respective delay means are input to the first and second band pass means, signals of only a certain frequency band are extracted, and
It is input to the first and second pulse generating means. This first, second
When the input signal reaches a certain level, the pulse generating means outputs a positive or negative pulse signal to detect the phase of each signal picked up by the first and second microphones. It Then, the two output signals of the first and second pulse generating means are input to the third pulse generating means, where the two signals are compared,
A positive or negative pulse signal is output only when they are present at the same time. Here, when there is a phase difference between the two input signals, the pulses do not exist at the same time, so the pulse signal is not output, and the pulses are output only when the phases are exactly the same. Therefore, the third
The presence or absence of a phase difference between the input signals can be detected by the pulse generating means.

The output signal of the third pulse generating means is input to the measuring means, whereby the amount of the output signal of the third pulse generating means is measured and the amount is input to the phase difference detecting means.
The phase difference detecting means changes the delay time of the signal in the second delay means within a certain width, and at that time, detects the delay time of the second delay means that maximizes the amount of the output signal of the measuring means, The difference between the value and the delay time of the first delay means (this value is fixed to a certain value) is obtained.

Thereby, the phase difference between the signals picked up by the first and second microphones is obtained.

That is, when the output signal from the measuring means becomes maximum, the phase difference between the signals time-delayed by the first and second delay means becomes zero. The difference between the set delay times is obtained as the phase difference between the signals applied to the first and second microphones.

The direction of the sound source on the front side of the microphone can be obtained by converting the direction of the sound source from this phase difference.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a sound source direction detecting device according to an embodiment of the present invention.

In FIG. 1, 1 and 2 are microphones for collecting sound, fixed between two points with a certain interval x, 3 and 4 are delay circuits for time delay of signals, and 5 and 6 are signals of a certain frequency band. Narrow-band bandpass filter that passes only, 7 and 8 are pulse generation circuits that generate pulse signals when the input signal exceeds a certain level, and 9 is input with two signals,
An AND circuit that generates a pulse signal only when the two signals are present at the same time, 10 is a pulse count circuit that counts the number of input pulse signals and outputs the value,
Reference numeral 11 changes the delay time of the signal in the delay circuit 4 within a certain width. At that time, the delay time of the delay circuit 4 at which the output value of the pulse count circuit 10 becomes maximum is detected, and from this delay time, the microphone 1, It is a phase difference detection circuit that converts the direction of the sound source of the signal added to 2.

The operation of the present embodiment configured as described above will be described below.

First, the signal applied to the microphones 1 and 2 is the delay circuit.
It is input to 3 and 4, and each is delayed for a certain time. However, the signal delay time in the delay circuit 3 is normally fixed to 1/2 of the maximum delay time width of the delay circuit, and the delay time in the delay circuit 4 is fixed.
Is controlled by.

The output signals of the respective delay circuits are input to the narrow band band pass filters 5 and 6, and the signals of only a certain frequency band are extracted. The output signals of the narrowband bandpass filters 5 and 6 are input to the pulse generation circuits 7 and 8 respectively, and when the input signals exceed a certain level, a pulse having a certain width is output, whereby the microphone 1 The phases of the respective signals added to the and 2, are detected. Pulse generator
The two output signals 7 and 8 are input to the AND circuit 9, and the same pulse as the input signal is output only when the two signals input here simultaneously exist. As a result, only when the phase difference between the signals applied to the microphones 1 and 2 is zero,
Since a pulse is output, the presence / absence of a phase difference between the two signals can be detected.

The output signal of the AND circuit 9 is input to the pulse count circuit 10, counts the number of pulses that are the input signal, and the value is input to the phase difference detection circuit 11.

The phase difference detection circuit 11 first changes the delay time of the signal in the delay circuit 4 within a certain width, and continuously delays the signal input to the delay circuit 4. Further, every time the delay time of the signal in the delay circuit 4 is changed, the output value of the input pulse count circuit 10 is read, and the maximum value of the value and the delay time of the delay circuit 4 when the maximum value is obtained are read. To detect. Then, the difference between the detected delay time and the delay time set in the delay circuit 3 is obtained. Thereby, the phase difference between the signals applied to the microphones 1 and 2 is obtained. The sound source direction can be detected by converting the angle of the sound source direction from this phase difference.

A method of converting the direction of the sound source from the phase difference will be described with reference to FIG.

In FIG. 3, it is assumed that the microphones 1 and 2 are fixed with a width of x, and that the sound source is sufficiently far away. The wavefront having the same phase as the signal picked up by the microphone 2 is the surface connecting the microphone 2 and the point A. Therefore, the microphones 1 and 2 have a distance difference y from the sound source.
Occurs. If the sound source direction is θ as shown in the figure, this distance difference y is Becomes

Further, when the sound velocity is v, the time difference y'of the signals of the same phase picked up by the microphones 1 and 2 is Becomes

Therefore, assuming that the phase difference obtained by the phase difference detecting means is A, Therefore, the sound source direction θ is Can be found at.

However, if the phase difference between the picked-up signals deviates by one wavelength or more, the direction cannot be detected. Therefore, the distance x between the microphones 1 and 2 is limited as follows.

However, is the pass frequency of the first and second band pass means. Further, λ is the wavelength of the signal.

FIG. 2 is a flow chart showing an algorithm of the operation of the phase difference detection circuit 11 in the embodiment of the sound source direction detecting apparatus of the present invention shown in FIG.

In FIG. 2, ti is the delay time set in the delay circuit 4 at time i, t _MIN is the initial value of the delay time of the delay circuit 4, and mti is the pulse count circuit at the delay time ti of the delay circuit 4. The output value of 10, m _MAX is the maximum value in the above mti, t is the delay time of the delay circuit 4 when m _MAX is obtained, Δt is the increase amount of the delay time set in the delay circuit 4, t _MAX is the maximum delay time of the delay circuit 4, T is the delay time set in the delay circuit 3, A is the delay time T of the delay circuit 3 and the output value from the pulse count circuit 10 is the maximum. Is the difference with the delay time of the delay circuit 4, θ is the direction of the sound source, v is the speed of sound, and x is the distance between the microphones 1 and 2.

First, the phase difference detection circuit 11 sets the delay time ti to t _MIN (step 21) and sets it in the delay circuit 4 (step 22). Then, the number of pulses mti counted by the pulse counting circuit 10 at that time is read (step 23), and m
Compare with _MAX (step 24). (However, m the initial value of _{the MAX} keep zero.) In this case, larger mti is from m _MAX, mti is set to m _MAX, in t, the delay time of the delay circuit 4 at that time is set ( Step 25). Also, mt
If i is not larger than m _MAX , the above processing is not performed.

Then, in step 26, the delay time ti is increased by Δt,
In step 27, the value is compared with t _MAX, and when ti is not larger than t _MAX , the flow returns to step 22 to set ti in the delay circuit 4, and the processing from step 22 onward is repeated.

As a result of comparing ti and t _MAX , when ti becomes larger than t _MAX , the delay time T of the delay circuit 3 and the delay time of the delay circuit 4 at the time when the output value of the pulse count circuit 10 becomes maximum. The difference A from t is obtained (step 28), and the direction θ of the sound source is converted from this (step 29). After that, the process returns to the start again, and the processes from step 21 onward are repeated. By repeating this process, the direction of the sound source can be obtained from the phase difference between the signals applied to the microphones 1 and 2 and this phase difference.

As described above, according to the present embodiment, the delay time of the delay circuit 4 is continuously changed within a certain width, and the pulse count circuit 10
By detecting the delay time of the delay circuit 4 that maximizes the output value of, the difference between the delay time and the delay time set in the delay circuit 3 is obtained, and the direction of the sound source is converted from this value. , The direction of the sound source located on the front side with respect to the microphones 1 and 2 can be easily obtained.

Advantageous Effects of the Invention First and second microphones fixed between two points having a certain distance, and first and second delay means for time-delaying signals applied to the first and second microphones, First and second band-passing means, which respectively receive the output signals of the first and second delay means and pass only signals in a certain frequency band,
When the output signal of the second bandpass means exceeds a certain level, a positive or negative pulse signal is output.
Pulse generating means and third pulse generating means for outputting a positive or negative pulse signal only when the two output signals of the first and second pulse generating means are present at the same time, and the third pulse generating means. The output signal of is input, the number of the signal within a certain time is measured, and the delay time of the measuring means for outputting the value and the second delay means is changed with a predetermined width,
The delay time of the second delay means that maximizes the output value from the measuring means is detected, the phase difference between the signals applied to the first and second microphones is detected from this delay time, and the phase difference is calculated from the phase difference. , The phase difference detection means for converting the sound source direction of the signal applied to the first and second microphones is provided, so that the direction of the sound source located on the front side with respect to the first and second microphones can be easily performed. It is possible to realize a sound source direction detecting device having a simple configuration capable of detecting with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of a sound source direction detecting device in one embodiment of the present invention, FIG. 2 is a flow chart showing an operation algorithm of a phase difference detecting circuit in the present embodiment, and FIG. 3 is a diagram showing a phase difference between input signals. FIG. 4 is a block diagram showing the arrangement of microphones showing the principle of converting the direction of a sound source, and FIG. 4 is a block diagram of a conventional example. 1,2 …… Microphone, 3,4 …… Delay circuit, 5,6 …… Narrow band bandpass filter, 7,8 …… Pulse generation circuit, 9…
… AND circuit, 10 …… Pulse count circuit, 11 …… Phase difference detection circuit.

Claims (1)

[Claims] 1. A first unit fixed between two points having a certain distance.
A second microphone; first and second delay means for delaying the signals applied to the first and second microphones;
There are output signals of the first and second bandpass means and output signals of the first and second bandpass means, which receive the output signals of the first and second delay means respectively and pass only signals of a certain frequency band. Only when the first and second pulse generating means for outputting a positive or negative pulse signal and the two output signals of the first and second pulse generating means are present at the same time when the level is exceeded. Or a third pulse generating means for outputting a negative pulse signal, and a measuring means for receiving the output signal of the third pulse generating means, measuring the number of the signals within a certain time, and outputting the value. The delay time of the second delay means is changed with a predetermined width to detect the delay time of the second delay means that maximizes the output value from the measuring means, and the first and second delay times are detected from this delay time. Detects the phase difference of the signals applied to the microphone, and from the phase difference, 1, the sound source direction detecting apparatus comprising comprises a phase difference detection means for converting the sound source direction of the second signal applied to the microphone.