JP2004328623A - Microphone device and sound source direction discriminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently output only the voice of a driver in a vehicle as the output waveform signal. <P>SOLUTION: A sound source direction discriminating device is provided with a microphone 2 which largely changes the phase by the direction of the sound source, a microphone 1 which is arranged in a near position and in a different phase from the microphone 2 depending on the direction of the sound source, a phase comparator (discrimination means) 3 which discriminates the direction of the sound source based on the relation of the phase of the waveform signals outputted from the respective microphones. The microphone device controls the output level of the waveform signal from the microphones based on the discriminating result of the phase comparator 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a microphone device that receives a sound wave output from a sound source and outputs an output waveform signal based on the sound wave, and a sound source direction determination device.
[0002]
[Prior art]
The microphone device receives a sound wave with a microphone, amplifies a waveform signal output from the microphone with an amplifier, and outputs the amplified signal. Generally, an omnidirectional microphone and a unidirectional microphone are used as microphones.
[0003]
The directional characteristics of a microphone device are basically determined by the directional characteristics of a microphone used in the device. The omnidirectional microphone has a substantially circular directional characteristic as shown in FIG. In addition, the unidirectional microphone has a substantially cardioid-shaped directional characteristic as shown in FIG.
[0004]
In recent years, in vehicles such as automobiles, car navigation systems and mobile communication systems have begun to spread widely. In such a system, for example, a car navigation system is operated based on a result of analyzing a voice received by a microphone device by a voice recognition device, or a voice received by the microphone device is transmitted by a mobile communication system.
[0005]
A microphone device used for such an application is desired to have a characteristic of reliably receiving a driver's voice and not receiving surrounding running noise and the like as much as possible. For this reason, it is common to arrange a unidirectional microphone as close to the driver in the vehicle as possible and toward the driver. At that time, there is also one that changes the directivity. (For example, see Patent Document 1).
[0006]
However, when a unidirectional microphone is used, although it is improved as compared with the use of an omnidirectional microphone, a large amount of surrounding running noise or the like is received. From the word unidirectional, we imagine the characteristic of high sensitivity only on the front, but in fact, the sensitivity of receiving sound waves from the side is only a few dB lower than the sensitivity when receiving from the front. is there.
[0007]
Therefore, the output signal of the microphone device includes a component based on the driver's voice, as well as a component such as ambient running noise. For this reason, the recognition rate of the speech recognition device deteriorates, and the communication quality of the mobile communication system deteriorates.
[0008]
Therefore, it is conceivable to use a microphone whose sensitivity in directions other than the front is lower than the directional characteristics of unidirectionality as the microphone to be used.
[0009]
Also, paying attention to the difference in the reception level between the driver's voice and the traveling noise, if the level of the microphone waveform signal exceeds a predetermined threshold level, it is conceivable to output this waveform signal as an output signal. Can be
[0010]
[Patent Document 1]
JP 2001-245396 A (Pages 2-5, FIG. 1).
[0011]
[Problems to be solved by the invention]
However, these conventional ideas cannot efficiently output only the driver's voice in the vehicle as an output waveform signal.
[0012]
Regarding the improvement of the directional characteristics of the former microphone, no microphone is actually more suitable than unidirectionality.
[0013]
For example, there is a microphone called super-directivity in which the sensitivity from the side is reduced and the shape of the directional characteristic is sharpened forward rather than unidirectional. However, a superdirective microphone needs a length longer than the wavelength of a sound wave in principle, and even a short microphone has a length of about 30 cm. For this reason, it is not realistic to install the device toward the driver's mouth.
[0014]
Further, there is a microphone having a directional characteristic of bidirectionality having low sensitivity from the side. The bidirectional microphone has a directivity characteristic of a substantially figure-eight shape as shown in FIG. In the case of bidirectionality, the side sensitivity is low, but the back sensitivity is about the same as that of the front. If sound from the back side is a problem, it seems to improve if you cover the back of the bidirectional microphone. However, when the back surface of the bidirectional characteristic is closed, the characteristic becomes close to the omnidirectional characteristic. An omnidirectional microphone is a microphone that mainly captures changes in air pressure generated by air movement, rather than direct movement of air by sound waves. Since the change in the atmospheric pressure is similarly generated by sound waves from any directions, the directional characteristics are non-directional. When one side of the diaphragm is closed, the movement of the diaphragm mainly depends on the change in atmospheric pressure. For this reason, the same applies to the case of unidirectionality, but if the periphery of the microphone diaphragm other than the front is closed, the directional characteristic of the microphone becomes close to non-directionality, contrary to the intention. It is.
[0015]
In the latter determination technique based on the threshold level, a desired level difference is required between the output level of the audio signal and the output level of the traveling noise. However, the output level of the voice signal greatly changes depending on the voice or inflection of the speaker, a change in the distance between the speaker and the microphone, or a noise level in the surroundings. Therefore, considering such fluctuations in the output level of the audio signal, an appropriate threshold level cannot be set, so that the voice is interrupted or running noise is constantly output. I do.
[0016]
In order to ensure an absolute level difference between the output level of the audio signal and the output level of the traveling noise, the distance between the driver and the microphone should be as short as possible. However, it is not realistic to force the driver to wear a headset with a microphone. As a matter of fact, mounting a microphone near the sun visor will shorten the distance from the driver. In this way, the distance can be reduced to about 30 cm to 40 cm. However, unlike the case where the headset is worn, the output level of the voice fluctuates because the distance between the speaker and the microphone fluctuates. In addition, the fluctuation level increases as the distance between the microphone and the driver decreases. For example, if the distance is 30 cm, the level of the audio signal will change about twice by moving back and forth by 5 cm. Therefore, it is very difficult to set an appropriate threshold level even if the location of the microphone is devised.
[0017]
Therefore, the inventor of the present application has found that, for example, in a bidirectional microphone or a microphone having a directional characteristic in which the sensitivity of the front and rear sides of the bidirectional microphone is changed to be different, the phase of the waveform signal changes depending on the sound wave receiving direction. Focusing on the fact that the above-mentioned problem can be solved well by utilizing this property, the present invention has been completed.
[0018]
That is, the present invention is to solve the above problem, and to obtain a sound source direction determination device capable of determining a relative direction of a sound source based on a phase difference between waveform signals output from a plurality of microphones. With the goal.
[0019]
Another aspect of the present invention is to provide a microphone device that determines a relative direction of a sound source based on a phase difference between waveform signals output from a plurality of microphones and controls an output waveform signal based on the determination result. With the goal.
[0020]
[Means for Solving the Problems]
The sound source direction determination device according to the present invention outputs a first microphone in which the phase of a waveform signal output greatly changes according to the direction of the sound source, and a waveform signal having a phase different from that of the first microphone depending on the direction of the sound source. A microphone, and a second microphone arranged sufficiently close to the wavelength of the first microphone and the sound wave, based on a result of comparing the phases of the waveform signals output from the respective microphones. Determining means for determining the direction of the sound source.
[0021]
The sound source direction determination device according to the present invention may further include, as a first microphone in which the phase of a waveform signal output according to the direction of the sound source greatly changes, the sensitivity on the front side and the sensitivity on the back side of the bidirectional characteristic are different. A microphone having a changed directional characteristic is used, and the direction of the microphone on the high sensitivity side is set in the direction opposite to the front of the device.
[0022]
The sound source direction determination device according to the present invention, the phase of the waveform signal output is different from each other depending on the direction of the sound source, and a plurality of microphones arranged closely, the waveform signal output from these microphones, or A calculating means for adding or subtracting a waveform signal obtained by shifting the phase of the waveform signal output from the microphone, and a waveform signal based on the waveform signal output from each microphone, which is output from the calculating means. A determination unit configured to determine a direction of the sound source based on a result of comparing phases of a waveform signal different from the waveform signal and a waveform signal output from the calculation unit.
[0023]
In the sound source direction determining apparatus according to the present invention, the ratio between the waveform signals to be added or subtracted can be varied by the arithmetic means for adding or subtracting the waveform signals.
[0024]
In the microphone device according to another aspect of the present invention, the phases of the output waveform signals are different from each other depending on the direction of the sound source, and are generated based on the waveform signals output from a plurality of microphones arranged close to each other. A determination means for determining the direction of a sound source by comparing the phases of a plurality of waveform signals; and an output level variable means for changing an output level of the waveform signal according to the determined direction of the sound source. It is.
[0025]
The microphone device according to another invention of the present application further includes a level detection unit that detects a level of a waveform signal based on a sound wave, and an output level variable unit that changes an output level. Is changed.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a microphone device and a sound source direction determination device according to an embodiment of the present invention will be described with reference to the drawings.
[0027]
Embodiment 1 FIG.
[0028]
FIG. 1 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 1 of the present invention.
[0029]
The sound source direction determination device mainly determines the omnidirectional microphone 1 as a second microphone, the bidirectional microphone 2 as a first microphone, and the phases of waveform signals output from these microphones 1 and 2. And a phase comparator 3 as determination means for outputting a phase determination signal that changes based on the results of these phase comparisons.
[0030]
Further, between the omnidirectional microphone 1 and the phase comparator 3, and between the bidirectional microphone 2 and the phase comparator 3, the amplitudes of the waveform signals output from these microphones 1 and 2 are amplified. An amplification amplifier 4 is provided.
[0031]
FIG. 2A is a directional characteristic diagram showing the directional characteristics of the omnidirectional microphone 1 shown in FIG. The directional characteristic curve of the non-directional characteristic has a substantially circular shape. That is, the amplitude of the waveform signal output from the omnidirectional microphone 1 is constant irrespective of the relative direction if the strength of the sound source is constant and the distance from the sound source is constant.
[0032]
FIG. 2B is a directional characteristic diagram showing the directional characteristics of the bidirectional microphone 2 shown in FIG. The directional characteristic curve of the bidirectional characteristic has an approximately figure-eight shape as if two circles were connected.
[0033]
That is, the amplitude of the waveform signal output from the bidirectional microphone 2 changes according to not only the distance between the bidirectional microphone 2 and the sound source but also the relative direction between the bidirectional microphone 2 and the sound source. Specifically, when a sound wave is applied to the bidirectional microphone 2 in a direction perpendicular to or parallel to the vibration surface (not shown), the sound wave in a direction perpendicular to the sound surface in a direction perpendicular to the vibration surface. Can output a waveform signal having a larger amplitude. In FIG. 2B, the vibration surface is provided on the horizontal axis.
[0034]
Further, the bidirectional microphone 2 has two directivity when there is a sound source above the horizontal axis in FIG. 2B and when there is a sound source below the horizontal axis in FIG. The phase of the waveform signal output from the microphone 2 is shifted by 180 degrees. In other words, the phase changes by 180 degrees near the position of the 8-shaped depression in the directional characteristic diagram of FIG. 2B.
[0035]
Hereinafter, a point at which the phase largely changes in the hollow portion of the directional characteristic diagram is also referred to as a phase singularity. In FIG. 2B, the portion A is a phase singularity.
[0036]
Note that the phase hardly changes in portions other than the phase singular point A in FIG. In other words, a waveform signal having almost the same phase can be obtained in any direction as long as it is above the horizontal axis in FIG. On the other hand, if the phase is lower than the horizontal axis in FIG. 2B, the phase is shifted by 180 degrees from the upper side, but a waveform signal having almost the same phase can be obtained in any direction.
[0037]
Therefore, for example, when a positive-phase sound wave is input from a sound source on the upper side of the horizontal axis in FIG. 2B and a positive-phase waveform signal is output from the bidirectional microphone 2, When a positive-phase sound wave is input from the lower sound source, a negative-phase waveform signal is output from the bidirectional microphone 2. Hereinafter, the direction in which the waveform signal of the positive phase is output from the bidirectional microphone 2 based on the positive phase of the sound wave is referred to as the front direction of the bidirectional microphone 2. The direction in which the waveform signal of the negative phase is output from the bidirectional microphone 2 based on the positive phase of the sound source is referred to as the back direction of the bidirectional microphone 2. The direction of the horizontal axis in FIG. 2B is described as the side direction of the bidirectional microphone 2.
[0038]
In addition, unlike the bidirectional microphone 2, the omnidirectional microphone 1 has no phase singular point A whose phase largely changes before and after the omnidirectional microphone 2, and has the same direction regardless of the relative direction of the sound source. Outputs a phase waveform signal.
[0039]
The omnidirectional microphone 1 includes a pressure microphone. The pressure microphone is realized by, for example, a dynamic microphone, a condenser microphone, an electret condenser microphone, or the like.
[0040]
This pressure type microphone basically has a structure in which the front side of the diaphragm is open and the back side is closed by a housing. There are two types of principles that the movement of air by sound waves moves the diaphragm. One is a movement method that directly receives the movement of air and follows the movement of air. The second is a movement in which the diaphragm is moved in response to a change in air pressure generated by the movement of air. Note that the latter two types of movements are overwhelmingly larger in the latter movement due to the atmospheric pressure. In the case of a pressure-type microphone, since the rear side is closed, the air pressure on the rear side of the diaphragm is constant, and the diaphragm is moved by a change in the atmospheric pressure on the front side. Since the movement due to the atmospheric pressure change is dominant, the pressure type microphone outputs a waveform signal according to the atmospheric pressure change at the location of the microphone. Since the pressure change around the microphone does not depend on the relative direction of the sound source, the sensitivity of the pressure type microphone is constant regardless of the relative position of the sound source, and the phase does not change depending on the direction of the sound source.
[0041]
In contrast, the bidirectional microphone 2 moves differently. As the bidirectional microphone 2, there is a velocity microphone, which is realized by, for example, a ribbon microphone.
[0042]
This velocity microphone has a structure in which the periphery of the diaphragm is open. When the periphery of the diaphragm is opened, if the size of the diaphragm is sufficiently small with respect to the wavelength of the sound wave, the pressure on the front side and the pressure on the back side of the diaphragm become exactly the same. In this case, the diaphragm is not moved by the change in the atmospheric pressure, but moves according to the direct movement of the air.
[0043]
In a velocity microphone, the direction of vibration of the diaphragm is opposite between the case where sound waves come from the front side of the diaphragm and the case where sound waves come from the back side of the diaphragm. For example, suppose that a certain sound source is arranged on the front side of the diaphragm, and the movement of air due to sound waves at a certain timing is in a direction toward the microphone. The diaphragm moves rearward in response to the movement of air coming from the front side. When the same sound source is arranged at the same distance on the rear side of the diaphragm and viewed at the same timing, the movement of air by sound waves toward the microphone is the same as when the sound source is on the front side. However, in this case, since the air comes from the rear side of the diaphragm, the diaphragm moves toward the front side. This movement is the reverse of when the sound source is on the front side. Since the waveform signal output of the microphone follows the movement of the diaphragm, in the case of a velocity microphone, the waveform signal output from the microphone differs depending on whether the relative direction of the sound source is the front side or the back side. The phases are reversed.
[0044]
In addition, when the pressure microphone and the speed microphone are arranged sufficiently close to the wavelength of the sound wave, and there is a sound source in front of the speed microphone, the speed microphone outputs the sound from the pressure microphone. A waveform signal having substantially the same phase as that of the waveform signal is output.
[0045]
FIG. 3 shows a case where sound waves coming from a sound source emitting a sine wave of a single frequency are received by a pressure type microphone as the omnidirectional microphone 1 and a velocity type microphone as the bidirectional microphone 2. 4 shows a waveform signal output from a microphone.
[0046]
In this figure, the waveform signal output from the pressure microphone is denoted by B. When the sound source is in front of the speed microphone, the output waveform of the speed microphone becomes a waveform signal A having substantially the same phase as the waveform B. In addition, the waveform signal output of the velocity microphone when the sound source is on the back side has an opposite phase to that when the sound source is on the front side.
[0047]
Therefore, when the waveform signal output of the velocity microphone as the bidirectional microphone 2 is viewed with the waveform signal output B of the pressure microphone as the omnidirectional microphone 1 as a reference, if the phases are substantially in phase as shown in FIG. If so, it can be said that the sound source is on the front side. Conversely, if the phases are substantially opposite as shown in FIG. 3C, it is understood that the sound source is on the back side.
[0048]
It is the phase comparator 3 in FIG. 1 that makes this determination. The phase comparator 3 determines, based on the waveform signal from the omnidirectional microphone 1, whether the phase of the waveform signal from the bidirectional microphone 2 is substantially the same or opposite. Then, for example, if the phases are almost the same, a high-level phase determination signal is output, and if the phases are almost the same, a low-level phase determination signal is output. Looking at the phase determination signal, if the level is high, the sound source is on the front side, and if the level is low, the sound source is on the back side.
[0049]
As described above, the sound source direction determining apparatus according to the first embodiment uses the sound source based on the phase relationship between the waveform signal output from omnidirectional microphone 1 and the waveform signal output from bidirectional microphone 2. The relative direction can be determined.
[0050]
Therefore, by using the sound source direction determining apparatus according to the first embodiment as shown in FIG. A or the back side B can be determined. Then, based on the result of this determination, for example, switches such as lighting can be turned on / off. When there is no sound from the front based on the determination result, the level of the surrounding noise can be reduced by reducing the amplitude of the waveform signal output.
[0051]
Embodiment 2 FIG.
[0052]
FIG. 5 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 2 of the present invention.
[0053]
The sound source direction determining apparatus mainly includes an omnidirectional microphone 1 as a second microphone and a first microphone having a directional characteristic in which the sensitivity on the front side and the sensitivity on the back side of bidirectionality are changed to be different. And a phase comparator 3 as a judging means for comparing the phases of the waveform signals output from the microphones 1 and 5 and outputting a phase judgment signal that changes based on the result of the phase comparison. And.
[0054]
An amplification amplifier 4 for amplifying the amplitude of the waveform signal output from the microphones 1, 5 is provided between the omnidirectional microphone 1 and the phase comparator 3 and between the microphone 5 and the phase comparator 3, respectively. Is provided.
[0055]
The above-described microphone 5 having the directional characteristics in which the sensitivity on the front side and the sensitivity on the rear side of the bidirectional microphone are changed so as to be different from each other can be realized by, for example, substantially covering the rear side of the bidirectional microphone 2. it can. In this case, for example, the directional characteristics are as shown in FIG.
[0056]
When the rear side of the diaphragm of the bidirectional microphone 2 is incompletely closed, when air vibrates with voice or the like, the movement of air on the rear side of the diaphragm is suppressed from the front side. The pressure on the front side and the pressure on the back side do not match. For this reason, the movement of the diaphragm is caused not only by the direct movement of the air but also by the element of the atmospheric pressure.
[0057]
As a result, as shown in FIG. 2C, the sensitivity on the back side of the bidirectional microphone 2 is lower than that on the front side, and the two phase singular points A are also displaced to the back side. Characteristics.
[0058]
This directional characteristic is hereinafter referred to as a hypercardioid characteristic. The hyper-cardioid characteristic in a narrow sense is a mixture of a certain ratio of the atmospheric pressure element, but here, all the characteristics having two phase singularities A and different front-side and rear-side sensitivities are hyper-cardioid characteristics. Will be described. In FIG. 2C, the larger one in the figure of 8 in the upper part is defined as the high sensitivity side, and the smaller ring is defined as the low sensitivity side. Note that the microphone 5 is described as a hypercardioid microphone 5.
[0059]
When the degree of sealing on the back side of the hypercardioid microphone 5 is further increased, the sensitivity on the back side further decreases, and the phase singularity A eventually becomes one, and the rise of the sensitivity on the back side disappears, The characteristics are as shown in FIG. The characteristics shown in this figure are called cardioid characteristics. Unidirectional microphones basically have cardioid characteristics.
[0060]
The components other than the hypercardioid microphone 5 are the same as the components of the same name in the first embodiment, and are denoted by the same reference numerals and description thereof is omitted.
[0061]
The second embodiment is characterized by a microphone installation method in addition to the components. The arrangement of the two microphones sufficiently close to each other is the same as in the first embodiment, but in the second embodiment, the low-sensitivity side of the hypercardioid microphone 5 is particularly installed facing the front of the device. That is, the direction of the hyper-cardioid microphone 5 on the high sensitivity side is installed in the direction opposite to the front of the device.
[0062]
The hypercardioid characteristics can have many characteristics depending on the shape of the closing side. Not only the position of the phase singularity A but also the phases on the high sensitivity side and the low sensitivity side change depending on the shape. Nevertheless, the hypercardioid microphone 5 in the second embodiment can be handled in the same manner as the bidirectional microphone 2 in the first embodiment.
[0063]
The relationship between the phase of the waveform signal output of the omnidirectional microphone 1 and the phase of the waveform signal output of the hypercardioid microphone 5 is as shown in B and A and C in FIG. 3, that is, approximately the same phase or approximately opposite. They are in a phase relationship.
[0064]
Therefore, similarly to the first embodiment, if the phase comparator 3 determines whether the waveform signal output of the omnidirectional microphone 1 is substantially in phase or out of phase, the sound source is located in front of the phase singular point A. It can be determined whether it is on the back side.
[0065]
As described above, the sound source direction determining apparatus according to the second embodiment determines the sound source based on the relationship between the phase of the waveform signal output from the omnidirectional microphone 1 and the phase of the waveform signal output from the hypercardioid microphone 5. The relative direction can be determined.
[0066]
Therefore, as shown in FIG. 6 in which the directional characteristics in the installed state of the two microphones 1 and 5 are superimposed, the sound source can be changed to the front side A of the sound source direction determining device by using the sound source direction determining device according to the second embodiment. Or in the surrounding direction B can be determined. Then, based on the result of this determination, for example, switches such as lighting can be turned on / off. When there is no sound from the front based on the determination result, the level of the surrounding noise can be reduced by reducing the amplitude of the waveform signal output.
[0067]
In particular, by setting the low sensitivity side of the hyper-cardioid microphone 5 to the front side of the sound source direction determination device as in the second embodiment, the sound source can be placed in a narrower angle range than when the bidirectional microphone 2 is used. You can determine whether there is. When the bidirectional microphone 2 is used, this range is fixed at 180 degrees. However, by using the hypercardioid microphone 5, this angle range can be narrowed. Further, by changing the structure of the hypercardioid microphone 5, the angle range for determining the position of the sound source can be freely changed to some extent.
[0068]
As a result, for example, by installing this sound source direction determination device on the sun visor of a car or on the ceiling near the sun visor, it is possible to focus on the driver and determine whether or not the user is speaking.
[0069]
Embodiment 3 FIG.
[0070]
FIG. 7 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 3 of the present invention.
[0071]
The sound source direction determination device mainly includes an omnidirectional microphone 1 as one of a plurality of microphones, a bidirectional microphone 2 as one of a plurality of microphones, and an omnidirectional microphone 1. A phase inverter 6 for inverting the phase of the waveform signal output, an adder 7 as arithmetic means for adding the output of the phase inverter 6 and the waveform signal output of the bidirectional microphone 2 at a specific ratio, and an adder And a phase comparator 3 as a determination unit that compares the phase of the output of the omnidirectional microphone 7 with the phase of the waveform signal output of the omnidirectional microphone 1 and outputs a phase determination signal that changes based on the result of the phase comparison.
[0072]
Amplifying between the omnidirectional microphone 1 and the phase comparator 3 and between the bidirectional microphone 2 and the adder 7 for amplifying the amplitude of the waveform signal output from these microphones 1 and 2 respectively. An amplifier 4 is provided.
[0073]
In the third embodiment, instead of using the hyper-cardioid microphone 5 in the second embodiment, a signal obtained by inverting the phase of the waveform signal output of the omnidirectional microphone 1 by the phase inverter 6 and the bidirectional microphone 2 A waveform signal obtained by adding the waveform signal outputs of the above-mentioned waveform signals by the adder 7 is used.
[0074]
When the sound wave comes from the front side, the omnidirectional microphone 1 and the bidirectional microphone 2 have substantially the same phase, and therefore have almost the opposite phase to the output of the phase inverter 6.
[0075]
Assuming that the amplitude of the output of the omnidirectional microphone 1 and the output of the bidirectional microphone 2 when the sound source is directly in front are the same, the output signal of the phase inverter 6 is halved, for example, and the adder 7 Suppose that it added in.
[0076]
When the sound source is in front, the output of the bidirectional microphone 2 and the output signal of the phase inverter 6 have opposite phases, so that the amplitude after addition is half of the output of the bidirectional microphone 2. At this time, the phase after the addition does not change. Also, when the sound source is on the back side, it has the same phase, so the amplitude is 1.5 times and the phase does not change. Further, when the sound source is in the side direction, the amplitude of the output of the bidirectional microphone 2 is small, so that the amplitude and phase after the addition are almost equal to the output signal of the phase inverter 6.
[0077]
Since the front and rear phases of the signal after addition by the adder 7 are opposite to those of the bidirectional microphone 2, there should be a phase singular point A where the phase is inverted somewhere in the middle. The phase singular point A disappears on the side of the directional microphone 2 where the phase singular point A was located. In this case, the phase singular point A of the signal after addition by the adder 7 is a point where the output of the bidirectional microphone 2 has the same phase as the front side and half the amplitude. Since the sensitivity of the bidirectional microphone 2 is approximately proportional to the cosine of the angle from the front, the point, that is, the phase singular point A, is approximately around ± 60 degrees from the front.
[0078]
The signal after addition by the adder 7 and the waveform signal from the omnidirectional microphone 1 are shown in FIG. The microphones used are the omnidirectional microphone 1 and the bidirectional microphone 2, but by using the phase inverter 6 and the adder 7, a signal corresponding to the hypercardioid microphone 5 can be generated. it can.
[0079]
Except for generating a signal corresponding to the hypercardioid microphone 5 by the adder 7, the other components are the same as those of the first embodiment having the same names, and are denoted by the same reference numerals and description thereof is omitted. .
[0080]
The phase of the signal entering the phase comparator 3 is exactly the same as in the first embodiment. Therefore, similarly to the first embodiment, if the phase comparator 3 determines whether the phase of the waveform signal output of the omnidirectional microphone 1 is substantially the same phase or the opposite phase, the sound source becomes the front of FIG. It can be determined whether it is on the side A or the back side B.
[0081]
As described above, the sound source direction determining apparatus according to the third embodiment uses the omnidirectional microphone 1 and the bidirectional microphone 2 to generate a sound source having a narrow angle range like the hypercardioid microphone 5. The relative direction can be determined.
[0082]
Therefore, it can be said that the same advantages as in the second embodiment, such as advantages in application, can be obtained.
[0083]
In the case of the hypercardioid microphone 5, the location of the phase singular point A is determined by the structure of the microphone, so that the location cannot be changed unless the microphone is recreated. However, in the case of the third embodiment, the location of the phase singularity A can be changed only by changing the input level of the adder 7.
[0084]
It is also advantageous that a general microphone can be used instead of the hypercardioid microphone 5.
[0085]
In FIG. 7, the bidirectional microphone 2 is installed so as to output a signal having the same phase as that of the omnidirectional microphone 1 to a sound source located on the front side, but may be installed in the opposite direction. In this case, the output of the non-directional microphone 1 and the output of the bidirectional microphone 2 for the sound source on the front side are generally waveform signals of opposite phases, so that the phase inverter 6 is omitted and the adder 7 is used as it is. The addition results in the same phase characteristics as above. However, since the waveform signal input from the adder 7 to the phase comparator 3 also has the opposite phase, the determination in the phase comparator 3 must be reversed.
[0086]
Embodiment 4 FIG.
[0087]
FIG. 9 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 4 of the present invention.
[0088]
The sound source direction determination device mainly includes an omnidirectional microphone 1 as one of a plurality of microphones, a bidirectional microphone 2 as one of a plurality of microphones, and an omnidirectional microphone 1. A phase inverter 6 for inverting the phase of the waveform signal output, a voltage control amplifier 8 for varying the output level of the phase inverter 6, and the output of the voltage control amplifier 8 and the waveform signal output of the bidirectional microphone 2 are added. An adder 7 serving as a calculating means for comparing the phase of the output of the adder 7 with the waveform signal output of the omnidirectional microphone 1 and outputting a phase determination signal that changes based on the result of the phase comparison And a phase comparator 3 as means.
[0089]
Amplifying between the omnidirectional microphone 1 and the phase comparator 3 and between the bidirectional microphone 2 and the adder 7 for amplifying the amplitude of the waveform signal output from these microphones 1 and 2 respectively. An amplifier 4 is provided.
[0090]
In the third embodiment, the phase singular point A is moved by adding the output of the omnidirectional microphone 1 whose phase is inverted to the output of the bidirectional microphone 2 by the adder 7. In the fourth embodiment, the voltage control amplifier 8 is added so that the addition amount can be changed, that is, the movement of the phase singular point A can be controlled.
[0091]
FIG. 8 shows that the addition ratio of the waveform signal from the bidirectional microphone 2 and the signal obtained by inverting the signal of the omnidirectional microphone 1 in the adder 7 is 2: 1. FIG. 10 shows this ratio set to 2: √3. The change in the ratio can be externally controlled by the voltage control amplifier 8.
[0092]
In the fourth embodiment, the other components are the same as those of the third embodiment except that the voltage control amplifier 8 is added and the ratio of addition by the adder 7 is variable. The description is omitted by attaching the reference numerals.
[0093]
The phase of the signal entering the phase comparator 3 is exactly the same as in the first embodiment. Therefore, similarly to the first embodiment, if the phase comparator 3 determines whether the waveform signal output of the omnidirectional microphone 1 is substantially in-phase or out-of-phase, the sound source becomes the front side A in FIG. It can be determined whether it is located on the rear side B.
[0094]
Further, the bidirectional microphone 2 can be installed in the opposite direction and the phase inverter 6 can be omitted, similarly to the third embodiment.
[0095]
As described above, the sound source direction determining apparatus according to the fourth embodiment uses the omnidirectional microphone 1 and the bidirectional microphone 2 to determine the relative position of a sound source in a narrow range such as the one using the hypercardioid microphone 5. The direction can be determined. Further, the position of the phase singular point A can also be controlled from outside.
[0096]
Therefore, the third embodiment is basically the same as the third embodiment, such as advantages in application, and further determines whether or not a sound source is within a zoom range as a microphone of a video camera with a zoom function in conjunction with the zoom. It is also possible to apply such as doing.
[0097]
Embodiment 5 FIG.
[0098]
FIG. 11 is a circuit diagram showing a microphone device according to Embodiment 5 of the present invention.
[0099]
The microphone device mainly includes an omnidirectional microphone 1 as one microphone among a plurality of microphones, a bidirectional microphone 2 as one microphone among a plurality of microphones, and these microphones 1 and 2. A phase comparator 3 as a judging means for comparing the phases of the output waveform signals with each other and outputting a phase judgment signal that changes based on the result of the phase comparison, and a waveform signal output from the bidirectional microphone 2 and a phase comparator. A voltage control amplifier 8 is provided as an output level variable unit that receives a phase determination signal from the comparator 3 and amplifies a waveform signal from the bidirectional microphone 2 with an amplification factor according to the level of the phase determination signal. The signal amplified by the voltage control amplifier 8 is output as an output waveform signal.
[0100]
Further, between the omnidirectional microphone 1 and the phase comparator 3, and between the bidirectional microphone 2 and the phase comparator 3, the amplitudes of the waveform signals output from these microphones 1 and 2 are amplified. An amplification amplifier 4 is provided.
[0101]
The voltage control amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 at an amplification factor according to the level of the phase determination signal, and outputs this as an output waveform signal. Specifically, the waveform signal from the bidirectional microphone 2 is amplified at a high amplification factor when the level of the phase determination signal is high, and at a low amplification factor when the level of the phase determination signal is low. Note that the low amplification factor may be 0%.
[0102]
The other components are the same as the components having the same names in the first embodiment, and are denoted by the same reference numerals and description thereof is omitted.
[0103]
When a sound source is arranged on the front side of the microphone device, the waveform signal from the omnidirectional microphone 1 and the waveform signal from the bidirectional microphone 2 have substantially the same phase. Outputs a judgment signal.
[0104]
Then, since a high-level phase determination signal is output from the phase comparator 3, the voltage control amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 at a predetermined high amplification factor. The signal amplified by the voltage control amplifier 8 is output as an output waveform signal.
[0105]
Conversely, if a sound source is arranged on the back side of the microphone device, the waveform signal from the omnidirectional microphone 1 and the waveform signal from the bidirectional microphone 2 are generally in opposite phases, so that the phase comparator 3 Outputs a phase determination signal.
[0106]
Then, since the low-level phase determination signal is output from the phase comparator 3, the voltage control amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 with a predetermined low amplification factor. The signal amplified by the voltage control amplifier 8 is output as an output waveform signal. If the amplification factor is 0%, the output waveform signal does not include a component based on the waveform signal from the sound source.
[0107]
As described above, the microphone device according to the fifth embodiment uses the relative direction of the sound source based on the relationship between the phase of the waveform signal output by the omnidirectional microphone 1 and the phase of the waveform signal output by the bidirectional microphone 2. Is determined, and the amplification factor of the waveform signal based on the sound wave is switched based on the determination result.
[0108]
Therefore, by using the microphone device according to the fifth embodiment, when there is a sound source on the front side of the microphone device, a waveform signal based on a sound wave from the sound source is amplified and output as an output waveform signal. be able to. If there is no sound source on the front side of the microphone device, the gain of the waveform signal is reduced.
[0109]
As a result, it is possible to obtain a directional characteristic that efficiently converts the sound of the sound source on the front side of the microphone device into an output waveform signal and does not convert the sound of the sound source on the back side of the microphone device into an output waveform signal.
[0110]
Note that, instead of the voltage control amplifier 8, a switch that is turned on / off in accordance with the level of the phase determination signal may be used. In this case, the amplification factor is switched between 100% and 0%. The same effect as in the fifth embodiment can be obtained by performing on-control when the phase determination signal is at a high level and off-control when the phase determination signal is at a low level.
[0111]
By the way, the fifth embodiment has a configuration in which the voltage control amplifier 8 is added to the first embodiment. Since the operation of the phase determination signal is the same as that of the first embodiment, the directional characteristics are in the same range as the determination of the sound source direction of the first embodiment.
[0112]
The part until the phase determination signal is obtained may be the second embodiment, the third embodiment, or the fourth embodiment other than the first embodiment. In this case, the directional characteristics can be limited to a narrower range, or the range can be changed.
[0113]
Embodiment 6 FIG.
[0114]
FIG. 12 is a circuit diagram showing a microphone device according to Embodiment 6 of the present invention.
[0115]
The microphone device mainly includes an omnidirectional microphone 1 as one microphone among a plurality of microphones, a bidirectional microphone 2 as one microphone among a plurality of microphones, and these microphones 1 and 2. A phase comparator 3 serving as a judging means for comparing the phases of the output waveform signals and outputting a phase judgment signal that changes based on the result of the phase comparison, and the level of the waveform signal output from the bidirectional microphone 2 And a level detector 9 as a level detecting means for outputting a gain control signal corresponding to the level, and multiplies the gain control signal by a phase determination signal output from the phase comparator 3 to generate a multiplied signal. The output multiplier 10 and the waveform signal from the bidirectional microphone 2 are input, and the higher the level of the multiplied signal from the multiplier 10 is, the higher the level is. Comprises a voltage control amplifier 8 as an output level varying means width ratio is increased, the. The signal amplified by the voltage control amplifier 8 is output as an output waveform signal.
[0116]
Further, between the omnidirectional microphone 1 and the phase comparator 3, and between the bidirectional microphone 2 and the phase comparator 3, the amplitudes of the waveform signals output from these microphones 1 and 2 are amplified. An amplification amplifier 4 is provided.
[0117]
The level detector 9 detects the level of a waveform signal output from the bidirectional microphone 2, and outputs a gain control signal corresponding to the level.
[0118]
FIG. 13 is an input / output characteristic diagram showing the relationship between the input signal level of the level detector 9 and the level of the gain control signal output from the level detector 9. The solid line is the input / output characteristic line of the level detector 9. A broken line is an input / output characteristic line of the linear amplifier.
[0119]
Then, as shown in FIG. 13, when the input level is lower than the predetermined first level, the level detector 9 outputs a gain control signal having a level proportional to the input level. When the input level is higher than the predetermined first level, the control signal is output at a substantially constant level.
[0120]
Note that the first level is, for example, when the microphone device according to the sixth embodiment is disposed above the driver's seat of a car, based on the volume of voice of a person sitting in the driver's seat in a normal car. An input level based on the voice volume, or a level slightly lower than that, may be set.
[0121]
The other components are the same as the components having the same names in the fifth embodiment, and are denoted by the same reference numerals and description thereof is omitted.
[0122]
When the sound source is arranged on the front side of the microphone device, the waveform signal from the omnidirectional microphone 1 and the waveform signal from the bidirectional microphone 2 are almost in phase, and the phase comparator 3 outputs the high-level phase determination signal. Is output.
[0123]
The level detector 9 outputs a gain control signal according to the level of the waveform signal from the bidirectional microphone 2. The multiplier 10 multiplies the gain control signal by the high-level phase determination signal and outputs the result as a multiplied signal.
[0124]
Then, the voltage control amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 at a predetermined high amplification rate according to the level of the multiplied signal. The signal amplified by the voltage control amplifier 8 is output as an output waveform signal.
[0125]
Conversely, if a sound source is arranged on the back side of the microphone device, the waveform signal from the omnidirectional microphone 1 and the waveform signal from the bidirectional microphone 2 are generally in opposite phases, so that the phase comparator 3 Outputs a phase determination signal.
[0126]
The level detector 9 outputs a gain control signal according to the level of the waveform signal from the bidirectional microphone 2. The multiplier 10 multiplies the gain control signal by the low-level phase determination signal and outputs the multiplied signal. Since the multiplication signal at this time is a multiplication with the low level, the multiplication signal is always at the low level.
[0127]
Then, the voltage control amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 at a predetermined low amplification rate according to the level of the multiplied signal. The signal amplified by the voltage control amplifier 8 is output as an output waveform signal. If the amplification factor is 0%, the output waveform signal does not include a component based on the waveform signal from the sound source.
[0128]
FIG. 14 shows input / output characteristics of the microphone device according to the sixth embodiment.
[0129]
When a sound source is present on the back side of the microphone device, a low-level phase determination signal is output from the phase comparator 3, so that the output waveform signal is based on the sound source, as shown by the input / output characteristic curve B in FIG. Regardless of the input level of the sound wave, the output level is always low.
[0130]
When a sound source is located on the front side of the microphone device, a high-level phase determination signal is output from the phase comparator 3, so that the output waveform signal has a bidirectional The output level corresponds to the input level of the sound wave input to the microphone 2.
[0131]
Specifically, for example, when the first level of the level detector 9 is set to be equal to or less than the voice volume of the person sitting in the driver's seat in a normal car, the range of FIG. As shown by the relationship with the range (the portion corresponding to the range of the input level (a) of the input / output characteristic curve A in FIG. 14), the voice of the person sitting in the driver's seat can be output at a substantially constant level. it can. The range of FIG. 14C is an output level range when a linear amplifier is used. As is clear from FIG. 14, the range of the output level shown in FIG. 14B is narrower than the range shown in FIGS. 14C and 14A. In other words, it can be said that the level is stable.
[0132]
When the volume is equal to or lower than the first level, the output waveform signal has a level lower than the predetermined level and changes linearly with the input level.
[0133]
As described above, the microphone device according to the sixth embodiment uses the relative direction of the sound source based on the relationship between the phase of the waveform signal output by the omnidirectional microphone 1 and the phase of the waveform signal output by the bidirectional microphone 2. It is possible to output an output waveform signal based on the sound wave from the sound source only when there is a sound source on the front side based on the judgment result. In other words, when the sound source is on the front side, sound up to a predetermined volume can be output linearly, and a sound with a higher volume can be output at a substantially constant level. On the other hand, when the sound source is on the back side, the level can be set to an extremely low level or not output at all.
[0134]
In particular, when the volume is higher than the first level, the output level becomes substantially constant, so that, for example, even if the level of the voice of the person sitting in the driver's seat changes due to the movement of the head position, it is easy to hear. It can be output as an audio signal of a certain level. It can also be suitably used as a voice input signal for a voice recognition device.
[0135]
By the way, in the sixth embodiment, since the phase determination signal has the same configuration as that of the first embodiment, the directivity also has the same range as that of the first embodiment.
[0136]
The part until the phase determination signal is obtained may be the second embodiment, the third embodiment, or the fourth embodiment other than the first embodiment. In this case, the directional characteristics can be limited to a narrower range, or the range can be changed.
[0137]
【The invention's effect】
With the sound source direction determination device according to the present invention, the relative direction of the sound source can be determined based on the phase relationship between the waveform signals output from the plurality of microphones.
[0138]
In the microphone device according to another aspect of the present invention, the relative direction of the sound source is determined based on the phase relationship between the waveform signals output from the plurality of microphones, and the output waveform signal is controlled based on the determination result. Can be.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a directional characteristic diagram showing directional characteristics of various microphones alone. (A) is the directional characteristic of an omnidirectional microphone, (B) is the directional characteristic of a bidirectional microphone, (C) is the directional characteristic of a hypercardioid microphone, and (D) is the directional characteristic of a unidirectional microphone. .
FIG. 3 is a waveform chart showing waveform signals output from a sound source that outputs a sinusoidal sound wave of a single frequency when the speed-type microphone and the pressure-type microphone receive the sound wave. .
FIG. 4 is a diagram showing directional characteristics in an installed state of two microphones used in the sound source direction determination device of FIG. 1;
FIG. 5 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 2 of the present invention.
6 is a diagram showing directional characteristics in a state where two microphones used in the sound source direction determination device of FIG. 5 are installed.
FIG. 7 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 3 of the present invention.
8 is a diagram showing the omnidirectional microphone used in FIG. 7 and the directional characteristics of the waveform signal generated by the adder.
FIG. 9 is a circuit diagram showing a sound source direction determining apparatus according to Embodiment 4 of the present invention.
FIG. 10 is a diagram showing the omnidirectional microphone used in FIG. 9 and signal characteristics of a waveform signal generated by an adder.
FIG. 11 is a circuit diagram showing a microphone device according to Embodiment 5 of the present invention.
FIG. 12 is a circuit diagram showing a microphone device according to Embodiment 6 of the present invention.
13 is a characteristic diagram showing input / output characteristics of the level detector in FIG.
14 is a characteristic diagram showing input / output characteristics of the microphone device of FIG.
[Explanation of symbols]
1 omnidirectional microphone
2 Bidirectional microphone
3 phase comparator (judgment means)
4 Amplification amplifier
5 Hyper Cardioid Microphone
6 phase inverter
7 Adder
8 Voltage control amplifier
9 level detector
10 Multiplier

Claims (6)

A first microphone in which the phase of the waveform signal output varies greatly depending on the direction of the sound source,
A microphone that outputs a waveform signal having a phase different from that of the first microphone depending on the direction of the sound source, and a second microphone that is arranged sufficiently close to the first microphone and the wavelength of a sound wave. When,
A sound source direction judging device, comprising: judging means for judging the direction of the sound source based on a result of comparing phases of waveform signals output from the first and second microphones. As the first microphone in which the phase of the waveform signal output varies greatly depending on the direction of the sound source,
While using a microphone with directional characteristics with the sensitivity on the front side and the sensitivity on the back side of the bidirectional characteristics changed differently,
2. The sound source direction judging device according to claim 1, wherein a direction on the high sensitivity side of the microphone is installed in a direction opposite to a front side of the device. Depending on the direction of the sound source, the phases of the output waveform signals are different from each other, and a plurality of microphones arranged close to each other,
Arithmetic means for adding or subtracting a waveform signal output from the microphone, or a waveform signal obtained by shifting the phase of the waveform signal output from the microphone,
A waveform signal based on the waveform signal output from the microphone, but different from the waveform signal output from the arithmetic means, and the result of comparing the phases of the waveform signal output from the arithmetic means; And a determining means for determining the direction of the sound source based on the sound source direction. 4. The sound source direction judging device according to claim 3, wherein a ratio of waveform signals to be added or subtracted is variable in said arithmetic means. To compare the phases of a plurality of waveform signals generated based on waveform signals output from a plurality of microphones that are different from each other in phase depending on the direction of the sound source and that are output from a plurality of microphones arranged close to each other. Determining means for determining the direction of the sound source,
Output level varying means for changing the output level of the waveform signal according to the determined direction of the sound source. Providing level detection means for detecting the level of a waveform signal based on sound waves,
6. The microphone device according to claim 5, wherein said output level changing means changes an output level also according to a detection result of said level detection means.

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