Sound pickup device

Abstract

To provide a binaural sound collection device which can collect sound including the transmission characteristics from the nose of a sound source in the front direction to both ears even if the binaural sound collection device does not have a head structure, and improves the quality of a sound image in the front direction and sound quality. [Solution] The sound collection system has a first microphone unit (103) placed on both the left and right ears, a second microphone (104) placed midway between the ears, and a signal processing unit (110) including a digital signal processing unit (114) equipped with a filter processing unit (111) that adds a transmission characteristic from the human nose to the eardrum to an audio signal propagating to the nose from a frontal sound source detected by the second microphone (104), and an adder unit (115) that is a synthesis processing unit that synthesizes the left and right microphone output signals from the microphone unit (103) and the output signal of the filter processing unit (111).

Description

Technical Field

[0001] The present invention relates to a binaural sound collection device that has a pair of left and right auricle structure parts including auricle parts imitating the left and right auricles of a human, and by installing microphones in the auricle structure parts, can collect three-dimensional sound.

Background Art

[0002] A binaural sound collection device is a sound collection system using microphones imitating the left and right auricle structures of a human. When listening to the collected stereo sound using stereo headphones or the like, compared with stereo sound collection using a general two-channel microphone, it is a system that enables a listener to listen to a sound with a sense of presence as if actually on the spot.

[0003] Conventional binaural sound collection devices having auricle parts are roughly classified into two types according to their shapes. The first shape, as shown in FIG. 1, not only has an auricle part 10 where a pair of left and right microphone parts 12 are installed, but also has a head 11, that is, the structure of a human head such as a nose and a face, and is called a so-called dummy head microphone. In this type of microphone, as shown in FIG. 3, the propagation of sound from a sound source S in the front direction is not only the direct wave propagation Hsl 1、 Hsr1, but also the propagation Hsdl1, Hsdr1 by diffracted waves that hit the nose part 1 from the sound source S and diffract on the surface of the nose and face and reach both ears, so that high-precision sound collection from the front direction is possible. On the other hand, because it has a head 11, it is large in shape and has a shape imitating a real head, so in some cases, it may give negative feelings such as eeriness to some people, and there is a problem that it is troublesome to handle.

[0004] Next, a second shape is shown in FIG. 2. The second shape has only the auricle structure 13 including the auricle part 10, and does not have a head structure corresponding to the nose or face. The left and right auricle structure parts 13 are connected by a connecting part 14 such as a rod shape or a rectangular parallelepiped case. In this case, by making the connecting part 14 smaller, there are advantages such as being lightweight, miniaturized, having good storability, and being easy to handle. However, as shown in FIG. 4, the propagation of sound from the front direction sound source S is mainly the direct waves Hsl2 and Hsr2 from the sound source S to both auricle microphones. Most of the sound waves Hc reaching the center between both ears pass through as they are, and the diffraction waves Hsdl2 and Hsdr2 from the face and the like are relatively low in level, or have characteristics completely different from the diffraction transmission characteristics by the head structure. For this reason, there has been a problem that the sound collection accuracy from a front direction sound source is particularly poor, and a so-called "mid-dropout" phenomenon of sound image localization occurs where the front direction sound image is blurred.

[0005] Also, as a common problem in these conventional examples, it is known that, particularly regarding the sound collection of a front direction sound source, the sound image localization position, the quality of the sound image, and further the timbre are different compared to the case where a listener listens with their own ears. Such differences from the sound that a listener listens to with their own ears are related to multiple factors. For example, as the first factor, there is the difference between the binaural sound collection device for sound collection and the shape of the listener's ears or head. Also, as the second factor, there is the fact that the sound collection system of a conventional binaural sound collection device cannot cover all the acoustic propagation paths by which a listener recognizes sound.

[0006] Regarding the problem that the shape of the auricle or head of the listener is different from that of the former binaural sound collection device, there is a method of directly mounting a microphone inside the listener's ear canal or near the ear. According to this method, since the transmission characteristics from the sound source to both ears directly reflect the characteristics of the listener, when the same listener listens to the sound collected using headphones as it is, the sound image localization and sound quality reproducibility are excellent, and it is possible to realize sound collection close to the sound that the listener is actually hearing on the spot. However, the method of mounting a microphone on the listener himself / herself in this way usually has problems that the position of the microphone moves according to the movement of the head, making it difficult to perform sound collection with a fixed direction, and noise is likely to be mixed in according to the movement of the listener.

[0007] In the latter case, the propagation path of sound waves from the sound source to both ears of the listener is not necessarily only the path that passes outside the human body, that is, outside the head and auricle, and reaches the eardrum. For example, in the sound propagation called bone conduction, it is known that the vibration of sound on the skin near the human auricle is transmitted to the cartilage near the auricle, propagates through the human body, and then is radiated from the outer wall of the ear canal and reaches the eardrum. In addition, the nasal cavity is connected to the eardrum through the nasal cavity, the eustachian tube, and the tympanic cavity, and sound waves from the nostrils are also involved in perception. Thus, when a human perceives sound, there is a sound propagation path that is perceived by propagating through the human body. In particular, the acoustic input signal from the nostrils is considered to mainly consist of sound waves from a sound source in the front direction and greatly affect the reproducibility of the sound source in the front direction. Recently, the opportunity to wear a mask has increased due to the spread of the novel coronavirus, etc., and the influence of sound wave propagation in the human body is being recognized again. That is, it has been pointed out that when wearing a mask, the clarity of sound and the sense of sound image localization are impaired compared to when not wearing a mask, and the propagation of the acoustic signal input from the nostrils is considered to be one of the factors in combination with the difference in the nasal shape due to the mask.

[0008] However, in the conventional binaural sound recording system, such propagation of acoustic signals inside the human body was not considered. For example, FIG. 3 shows the sound propagation path from the sound source S in the conventional example of FIG. 1 to the microphone unit 12. In this example, if the sound pressure levels Pl1 and Pr1 at both ears are the transfer characteristics of the direct wave from the sound source S to both ears as Hsl1 and Hsr1, and the transfer characteristics due to the diffracted wave that hits the nose part 1 from the sound source S, diffracts on the nose and the face surface, and reaches the ears as Hsdl1 and Hsdr1, these are the combined characteristics. The audio signal actually picked up by the microphones placed in the left and right auricle structure parts is, (Equation 1) Pl1 = (Hsl1 + Hsc1) × S ···(1) (Equation 2) Pr1 = (Hsr1 + Hsc1) × S ···(2) In this example, the acoustic signal from the front - direction sound source S can include the diffraction component by the facial part and the nose part of the head structure in the sound - pickup signal. Especially in the sound - pickup of the front - direction sound source, it is improved compared to the conventional example shown in FIG. 2. However, even in this method, only the propagation of the acoustic signal outside the human body from the sound source to both ears is picked up, and there is no pickup of the acoustic signal that passes through and propagates inside the body input from the nostril part. Still, in terms of the reproducibility of the front - direction sound source, it could not be said to be sufficient.

[0009] Furthermore, in the sound propagation path from the sound source S to the microphone in the conventional example of FIG. 2 shown in FIG. 4, if the transfer characteristics from the front - direction sound source S to the microphone are Hsl2 and Hsr2, not only is it difficult to pick up the acoustic signal that passes through and propagates inside the body input from the nostril part, but also the diffracted wave at the connection part can hardly be picked up. The sound pressure levels Pl2 and Pr2 at the two - ear microphones are approximately represented by the following equations. (Equation 3) Pl2 = (Hsl2) × S ···(3) (Equation 4) Pr2 = (Hsr2) × S ···(4) That is, the sound wave Hc radiated from the sound source S to the mid - point between the left and right of the two - ear microphones is hardly picked up by the microphones placed at both ears, which is a factor affecting reproducibility such as the phenomenon of sound leakage in the front - direction sound source.

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described above, in the shape of a binaural sound collection device, in a binaural sound collection device with a shape that mimics not only the auricle structure but also the head structure, sound collection from a sound source in the front direction can include diffraction signals caused by the head, but having a head structure not only increases the size and weight of the shape, but also, due to its spherical shape, there is a problem that it is cumbersome to handle. Also, due to its shape similar to that of a real head, there is a problem that it may give negative feelings such as eeriness when used among an audience.

[0011] On the other hand, in the shape of a binaural sound collection device, in a binaural sound collection device that reproduces only the auricle structure part and does not have a head structure, especially when collecting sound from a sound source in the front direction, the direct waves from the sound source to both ears can be faithfully collected, but the diffraction waves from the facial area and the nose cannot be faithfully collected. As a result, there is a problem that the sound image in the front direction blurs, that is, the so-called "dropout" phenomenon of sound image localization occurs.

[0012] Also, regardless of the fixed binaural sound collection device, there is a method of directly attaching a microphone inside or near the ear canal of the listener. According to such a method, the sound image and the reproducibility of the sound quality when the listener listens to the sound collected by himself / herself through headphones are good, but there are problems that the position of the microphone moves according to the movement of the head, making it difficult to collect sound with the direction fixed for a long time, and noise is easily mixed in according to the movement of the listener.

[0013] Furthermore, in any conventional binaural sound collection device or method of attaching a microphone directly to the listener's auricle, among the microphones placed on the auricle, only the sound signal that propagates from the outside of the human body to the eardrum position is collected, and the sound signal that propagates from inside the human body, particularly from the nostrils through the nasal cavity, eustachian tube, and tympanic cavity to the eardrum, is not collected. Therefore, there has been a problem that the sound signal caused by internal human body propagation is missing, and particularly, the clarity, sound image localization, and timbre are impaired when collecting and reproducing a sound source in the front direction.

Means for Solving the Problems

[0014] In order to solve the above problems, the sound collection system according to the invention of claim 1 is a sound collection system comprising a pair of left and right auricle structure parts including auricle parts imitating the left and right auricles of a human, a connecting part that holds and connects the left and right auricle structure parts at a certain interval, and a pair of left and right microphones installed on the left and right auricle structure parts, characterized by providing a detection means for detecting a sound signal transmitted from a sound source in the front direction to the midpoint between the left and right of the microphones, a filter processing part for adding the transmission characteristics from the human nose to the eardrum to the detected sound signal, and a synthesis processing part for synthesizing the output signal of the filter processing part with the output signals of the left and right microphones. According to this method, not only the sound collection by the propagation path outside the head from the sound source to the microphones placed on the left and right auricle parts is possible, but also the sound collection reflecting the transmission characteristics of the propagation path inside and outside the head from the sound source through the nose to the eardrum is possible, and particularly, the clarity and sound image localization of the sound collection from the front direction can be improved.

[0015] Also, the sound collection system according to the invention of claim 2 is characterized in that the detection means is a second microphone provided at the midpoint between the left and right of the pair of left and right microphones. According to this method, the sound signal from the sound source to the nose can be accurately detected using a microphone, and by reflecting the transmission characteristics of the propagation path inside and outside the head from the nose to the eardrum through filter processing, particularly, the clarity and sound image localization of the sound collection from the front direction can be improved.

[0016] Also, the sound collection system according to the invention of claim 3 is characterized in that the detection means is a center plane sound source extraction process for extracting a center plane direction sound source signal from the output signals of the pair of left and right microphones. According to this method, even without the second microphone, the voice signal from the sound source in the front direction to the nose can be accurately detected, and by reflecting the transmission characteristics due to the propagation path inside and outside the head from the nose to the eardrum through filter processing, in particular, the clarity and sound image localization of sound collection from the front direction can be improved.

[0017] Also, the sound collection system according to the invention of claim 4 is characterized in that the detection means and the filter processing unit can be detached between the pair of left and right auricle structure parts, is a semi-cylindrical structure having a height longer than the vertical length of the auricle part, and the distance from the front end part in the front direction to the ear hole position in the auricle part is 120 mm or more and 200 mm or less when worn. According to this method, by adding a semi-cylindrical structure or a frustum of a sphere structure and performing filter processing as a front direction sound source detection and acoustic circuit, the transmission characteristics due to diffraction outside the head from the nose to the eardrum are reflected, and in particular, the clarity and sound image localization of sound collection from the front direction can be improved.

[0018] Also, the sound collection system according to the invention of claim 5 is characterized in that the detection means is the first transmission characteristic from the front direction sound source to the pair of left and right microphones, and the filter processing unit is the difference between the first transmission characteristic and the second transmission characteristic from the front direction sound source of the listener to the left and right ear holes of the listener. According to this method, the audio signals input into a pair of left and right microphones from the front direction are respectively divided by the transfer characteristics from the front-direction sound source measured in advance to the pair of left and right microphones, and are detected as signals with the same phase and the same level. Further, by performing filter processing to give the transfer characteristics from the front-direction sound source of the listener to both ears via the nose, accurate sound collection can be performed to give the transfer characteristics to both ears of the listener with respect to the front-direction sound source, and in particular, the clarity and sound image localization of the sound collection from the front direction can be improved.

[0019] Also, the sound collection system according to the invention of claim 6 is as described in claim 5 A measurement unit is provided that includes an external microphone unit that can be detached and attached inside the left and right ear canals of the listener, an audio output unit that outputs a test signal to an external speaker, and a measurement means that measures the transfer characteristics from the external speaker to the external microphone. The second transfer characteristic is obtained by the measurement unit. According to this method, the transfer characteristics from the front-direction sound source of the listener to both ears can be changed within this sound collection system, and it becomes possible to provide a sound collection system that improves the clarity and sound image localization of the sound collection from the front direction for any listener.

[0020] Also, the sound collection system according to the invention of claim 7 is as described in claims 1 to 6 The transfer characteristics from the human nose to the eardrum include at least the transfer characteristics due to the diffraction wave on the face surface from the nose to the ear canal part. According to this method, even a binaural sound collection device that does not have a diffraction part by the head as an acoustic circuit, a binaural sound collection device having a head structure, or sound collection from a front-direction sound source equivalent to the listener becomes possible, and it becomes possible to provide a sound collection system that improves the clarity and sound image localization of the sound collection from the front direction.

[0021] Also, the sound collection system according to the invention of claim 8 is as described in claims 1 to 6 The transfer characteristics from the human nose to the eardrum include at least the transfer characteristics inside the body from the human nostril part, via the nasal cavity, eustachian tube, and tympanic cavity, to the eardrum. According to this method, it becomes possible to pick up the sound of the voice signal propagating through the body from the nostrils, and it becomes possible to provide a sound collection system that improves the clarity and sound image localization feeling of sound collection from the front direction.

[0022] In addition, the sound collection system according to the invention of claim 9 In a sound collection system using a pair of earplug microphones inserted into the left and right ear canals of a human, detection means for detecting a voice signal transmitted from a front direction sound source to the midpoint between the left and right ear canals, a filter processing unit for adding a transmission characteristic from the nose to the eardrum of a human to the detected voice signal, and an output signal of the filter processing unit are synthesized with the output signals of the left and right microphones It is characterized by having a combining processing unit. According to this method, since the propagation path outside the head from the sound source to the microphones placed on the left and right auricles of the listener is the actual head of the listener, not only can optimal sound collection be achieved for the listener, but also the sound collection can reflect the transmission characteristics of the in-vivo and in-vitro propagation path from the front direction sound source through the nose to the eardrum. In particular, the clarity and sound image localization feeling of sound collection from the front direction can be improved.

[0023] In addition, the sound collection system according to the invention of claim 10 A sound collection device comprising a pair of left and right auricle structure parts including auricle parts imitating the left and right auricles of a human, a connecting part for holding and connecting the left and right auricle structure parts, and a pair of left and right microphones installed on the left and right auricle structure parts, The connecting part is characterized in that it can be expanded and contracted. According to this method, since the inter-aural length of the microphones can be adjusted to the inter-aural length corresponding to the listener's both ears, the transfer function from the front direction sound source to both ears can be made closer, and the clarity and sound image localization feeling of sound collection from the front direction sound source can be improved.

Effect of the Invention

[0024] According to the present invention, even a fixed microphone system having only an auricle portion and no head structure can achieve sound collection with a microphone device having a head structure or reflecting the sound transmission characteristics of a real head. In addition to sound collection by the propagation path outside the head from the sound source to the microphones placed in the left and right auricle structures, sound collection can also reflect the transmission characteristics of the internal body path from the sound source through the nostrils, eustachian tubes, tympanic cavities to the eardrums, and in particular, the clarity and sound image localization of sound collection from the front direction can be improved.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0026] Hereinafter, embodiments of the sound collection device and method according to the present invention will be described with reference to the drawings. As shown in the conventional example of FIG. 4, in a binaural sound collection system having no conventional head structure, the sound propagation path from a front direction sound source to the microphones placed at both auricle portions is mainly due to the direct waves Hsl2 and Hsr2 from the sound source to both ears. The sound wave Hc heading toward the center between both ears passes directly through the center between both ears and is hardly collected, or even if it is collected, the level is small and completely different from the diffraction wave of the listener's head. Therefore, when the transfer functions of the direct waves are Hsl2 and Hsr2, the sound pressures Pl2 and Pr2 at the binaural microphone portions 12 placed at the left and right auricle structure portions from the front direction sound source S are approximately expressed by the following equations. (Equation 5) Pl2 = (Hsl2) × S ···(5) (Equation 6) Pr2 = (Hsr2) × S ···(6)

[0027] However, as shown in Fig. 5, the sound propagation from the actual front - direction sound source to the positions of the eardrums of both ears of the listener includes not only the direct waves (a) Hsl3 and Hsr3 but also the head diffraction waves (b) Hsdl3 and Hsdr3 from the listener's nose 56. Furthermore, there are also internal - path sounds such as (c) Hsnr3 and Hsnr3 that propagate from the nostrils 50 of the nose 56, through the nasal cavity 51, the eustachian tube 52, the tympanic cavity 53, and then inside the eardrum 54. Therefore, generally in a binaural sound - collecting device, in order to improve the clarity and sound - image localization of sound collection from a front - direction sound source, which is considered difficult to reproduce, it is necessary to further consider the transfer functions from the nose 56 to the positions of both eardrums. In Fig. 5, let the left - and - right transfer functions due to the direct wave from the front - direction sound source S be Hsl3 and Hsr 3、 Let the left - and - right transfer functions due to head diffraction be Hsdl 3、 Hsdr 3、 Let the left - and - right transfer functions due to the internal path be Hsnl 3、 If we set them as Hsnr3, the left - and - right sound pressures Pl3 and Pr3 at the eardrum positions are expressed by the following equations. (Equation 7) Pl3 = (Hsl3 + Hsdl3 + Hsnl3)×S ···(7) (Equation 8) Pr3 = (Hsr3 + Hsdr3 + Hsnr3)×S ···(8)

[0028] Therefore, in order to achieve sound - collection characteristics similar to those of sound collection by the listener's ears for a front - direction sound source using a binaural sound - collecting device without a head structure, it is necessary to make the transfer functions in (5) and (6) approach those in (7) and (8). The present invention provides a transfer function that combines not only the direct wave but also the transfer functions (Hsdl3 + Hsnl3) and (Hsdr3 + Hsnr3) from the nose 56 to the eardrum 53 for a front - direction sound source S. Furthermore, the transfer functions Hsl2 and Hsr2 of the microphone device itself from the front - direction sound source S are combined with the external - path transfer functions Hsl 3、 Hsr3 or Hsl3 + Hsdl including the diffraction part 3、By converting to Hsr3+Hsdr3, a binaural sound collection system with good forward sound image localization and sound quality can be realized even with a binaural sound collection device without a head structure.

Embodiment

[0029] Fig. 7 shows a first embodiment of the sound collection system according to the present invention. The configuration having a pair of left and right auricle parts 102, a pair of left and right auricle structure parts 100 that hold the auricle parts 102, a connecting part 101 that connects the left and right auricle structure parts at a certain length, and a pair of left and right first microphone parts 103 installed on each of the left and right auricle parts is the same as the conventional example shown in Fig. 2. In the present invention, further, a second microphone 104 is provided at an intermediate position between the left and right auricle parts, and a signal processing part 110 that performs signal processing on the output signals of the first and second microphones is provided. Note that the installation position of the first microphone part 103 inside the auricle part is originally the eardrum position at the deepest part of the external auditory canal. However, since the transmission characteristics of the external auditory canal are included in its propagation characteristics during reproduction with headphones, considering reproduction with headphones, it may be installed at the entrance of the external auditory canal. Also, here, it is assumed that the transmission characteristics from the headphones to the microphone position are compensated to be flat or flat.

[0030] Details of the signal processing part 110 in this embodiment are shown in Fig. 8. In Fig. 8, the output signals of the first microphone parts 103 placed on both the left and right ears and the second microphone 104 placed at the intermediate part between both ears are input to the signal processing part 110. The signal processing part 110 includes an amplifier 112 that amplifies each microphone signal, an A / D converter 113 that converts the amplified analog signal into a digital signal, and a digital signal processing part 114 that performs digital signal processing on the input microphone signals. Further, the digital signal processing part is provided with a filter processing part 111 that performs filter processing on the second microphone signal and an adder 115 that adds the output of the filter processing part to the left and right first microphone signals.

[0031] The details of the filter processing unit 111 are shown in FIG. 9. The filter processing unit 111 is composed of a head diffraction part filter 116, a body path part filter 117, delay devices 118 and 119 that give a delay time to the output of each filter, attenuators 120 and 121 that adjust the output signal levels of the respective delay devices, and an adder 122 that adds the outputs of the respective attenuators. Either both or one of the head diffraction part filter 116 and the body path part filter 117 is included. Further, in the head diffraction part filter 116, a filter is configured to simulate the transmission characteristics from the nose of a dummy head microphone having a head structure, diffracting through the face surface and reaching the eardrum part. The transmission characteristics from the nose to the eardrum part due to diffraction by the head surface are obtained as the difference in the transmission characteristics from the sound source to the positions of both ear holes with and without a head structure, either by simulation or as measured values. An example of the diffraction characteristics obtained in this way is shown in FIG. 10. In this characteristic, there is a peak value around 5 kHz to 6 kHz, and the level is -20 dB to -15 dB with respect to the direct wave at 1 kHz. Therefore, the level of the diffracted wave with respect to the direct wave is small, and the difference due to diffraction only needs to be considered in the above peak frequency band.

[0032] Next, in FIG. 9, the body path part filter 117 is the transmission characteristic of the body path part filter that reaches the eardrum part via the nasal cavity, the eustachian tube, and the tympanic cavity from the nostril part, and an example of the characteristic is shown in FIG. 11. The characteristic is calculated by placing a speaker as a sound source at the nostril part of a human and measuring with a microphone placed near the eardrum in the external auditory canal or by simulation. Here, it has a band-pass characteristic with a peak characteristic around 3 kHz, that is, a band from 3 kHz to 5 kHz. That is, a signal in the band from 3 kHz to 5 kHz is input to the eardrum from the tympanic cavity side of the eardrum. Therefore, in the filter part, the signal that has passed through the band-pass filter in this band is inverted in phase and added at the adder 122. Also, the level at the attenuator 119 is adjusted using the original sound comparison method or the like. Further, in the delay devices 118 and 119, a delay time corresponding to the time difference between the transmission time from the sound source directly to both ears and the transmission time from the sound source via the nose to the eardrum, for example, a delay time of about 150 μs is added.

[0033] A filter having the characteristics shown in FIGS. 10 and 11 above is provided in the filter unit 111. The filter characteristics are configured by a FIR filter, or by a peak filter or a band-pass filter that matches the frequency characteristic shape in the vicinity of the peak frequency as shown in FIGS. 12 and 13. Here, an example of the in-body path filter is shown. Also, the present invention can be applied to a dummy head microphone system having a head structure as shown in FIG. 1. The difference from the microphone system in FIG. 2 is the presence or absence of the head diffraction signal of the sound wave coming from the front direction in the head. Therefore, since the head diffraction part is already included in the sound collection data, the same configuration as in FIG. 7 can be adopted, and in the filter processing unit in FIG. 9, only the in-body path unit filter 117 needs to be provided. As described above, by adding the transmission characteristics from the nose to the eardrum position to the output signal of the second microphone 104 placed in the middle part between the two ears by the filter processing unit 111 and synthesizing it with the output signals of the pair of left and right first microphones 103, even a binaural sound collection device without a head structure can perform sound collection having head diffraction and in-body path characteristics for a front direction sound source.

[0034] FIG. 14 shows a second embodiment of the sound collection device according to the present invention. A configuration having a pair of left and right auricle parts 102, a pair of left and right auricle structure parts 100 that hold the auricle parts 102, a connecting part 101 that connects the left and right auricle structure parts at a certain length, and a pair of left and right first microphone parts 103 installed on each of the left and right auricle parts is the same as the conventional example shown in FIG. 2, and a signal processing unit 150 that performs signal processing on the output signal of the microphone part 103 is provided. FIG. 15 shows the details of the signal processing unit 150. The left and right input signals from the microphone unit 103 are amplified and digitized by an amplifier 152 and an A / D converter 153, and then input to a digital signal processing unit 154. In the digital signal processing 154, a front sound source extraction processing unit 156 that extracts a front direction sound source by comparing the amplitudes and phases of the left and right input signals, and a filter processing unit 151 that adds the transmission characteristics of the propagation path from the nose to the left and right eardrums to the detected front direction sound source signal are provided.

[0035] The difference from the first embodiment is that the front-direction sound source is not picked up by the second microphone from the front-direction sound source signal, but is extracted from the correlation between the left and right signals of the microphone units 103 placed on the left and right ears. FIG. 16 shows the details of the front sound source extraction unit 156. The digital signals from the left and right two-channel microphones 103 are converted into the frequency domain by the FFT processing 157. The left and right audio signals converted into the frequency domain are input to the phase comparison processing 158 and the level comparison processing 159. Here, the input signal from the front-direction sound source can be estimated by the phase difference and the level difference. From the relationship between the interaural phase difference and the level difference from the sound source to both ears, the sound source from the dead front is almost the same level and in-phase on the left and right. For example, taking the sound source within the range of ±10° from the front as the front direction as an example, from the relationship between the interaural time difference and the interaural level difference regarding the well-known sound image localization, when there is a sound source direction angle difference of 10°, the interaural time difference is about 50 μs, the interaural level difference is about 3 dB, and at this time the interaural phase difference is about 18° at 1 kHz, for example. Therefore, in the phase comparison processing 128, for each frequency bin in the frequency domain, a signal with a phase difference that can be regarded as the front direction, here a signal with a phase difference within 18° between the left and right as an example, is extracted. Further, for the extracted frequency bin signal, the level difference is compared in the level comparison processing 129. Here, a signal with a level difference within 3 dB between the left and right is extracted. By performing inverse FFT processing on the frequency bins extracted in this way by the IFFT unit 160, the front-direction sound source signal can be extracted from the left and right microphone signals. In addition, according to this extraction method, not only the front direction but also the sound sources in all directions of the median plane are extracted. However, since the sensitivity of the rear sound source to sound image localization and sound quality is lower than that of the front sound source, by processing the median plane sound source as the front sound source and improving the sound pickup accuracy of the front sound source, the advantages of improving the sound image localization and the sound quality are greater.

[0036] By performing filter processing on the front-direction sound source signal extracted from the left and right microphone signals in this way by the filter unit 151 in FIG. 15, a binaural sound pickup device with improved front-direction localization feeling and tone color can be realized. The processing in the filter unit 151 is the same as that in FIG. 9 in the first embodiment.

[0037] FIG. 17 shows a third embodiment of the sound collection device according to the present invention. The conventional example microphone device shown in FIG. 2 has a detachable portion 200 formed by a detachable semi-cylindrical structure. FIG. 17(a) is a front view, a top view, and a side view in an uninstalled state, and FIG. 17(b) shows the detachable portion 200 and the front view, the top view, and the side view after installation. As seen in the side view, the detachable portion 200 has a height dimension that is at least higher than the auricle portion. Also, the surface distance 203 from the tip portion 201 where sound waves from a front sound source first reach to the ear hole portion 202 where the microphone is attached is set to be 120 mm or more and 200 mm or less, which corresponds to the distribution of the distance from the human nose tip to the ear hole. Sound waves coming from the front sound source of this microphone device are detected without passing through at least the sound waves reaching from in front of the auricle portion by attaching the detachable portion 200, and a transfer function of diffraction propagation is added by diffracting on the surface of the detachable portion and input to both ears. That is, this structure functions as a detection means for detecting a front direction sound source, and at the same time, the transfer characteristics due to diffraction propagation on the surface of the structure serve as an acoustic filter, functioning as a filter means. As a result, it is possible to collect the diffracted wave of the front direction sound source and improve sound image localization and sound quality.

[0038] In the present invention, the detachable portion 200 has been described as a cylindrical structure, but as long as it has a structure that provides the above surface distance from the front direction tip portion to the ear hole portion, it can be replaced with a structure such as a barrel-shaped frustum or a structure imitating the face of a person with a nose. Also, a second microphone can be provided inside the nose portion to add the sound collection function of the body path shown in the first embodiment. Also, by adopting a detachable structure, it is possible to select a surface distance close to both ears of the listener, that is, a diffraction distance, and it is possible to give characteristics close to the diffraction characteristics of the listener. FIG. 18 shows another example of the present invention. This is a more lightweight example in which the detachable portion 300 is formed as a face mask structure made of a film-like plastic plate and is attached by elastic rubbers 301 that can be stretched and contracted to both auricle portions. By changing the lateral width of the plastic plate, it is also possible to adjust according to the diffraction distance of the listener.

[0039] FIG. 19 shows a fourth embodiment of the sound collection device according to the present invention. The configuration having a pair of left and right auricle portions 102, a pair of left and right auricle structure portions 100 that hold the auricle portions 102, a connecting portion 101 that connects the left and right auricle structure portions at a certain length, and a pair of left and right first microphone portions 103 installed on each of the left and right auricle portions is the same as the conventional example shown in FIG. 2. In the present invention, a signal processing unit 400 that performs signal processing on the output signal of the microphone is provided. FIG. 20 shows the details of the signal processing unit 400. In the signal processing unit 400, the input voice signal from the microphone unit 103 is amplified and converted into a digital signal through an amplifier 401 and an A / D converter 402, and then passed to a filter processing unit 404 in a digital signal processing unit 403. The details of the filter processing unit 404 are shown in FIG. 21. In the example of FIG. 21(a), in the first transfer characteristic 405, for each of the left and right input signals, the reciprocals 1 / Hsl2 and 1 / Hsr2 of the transfer functions from the front direction sound source of the present microphone device to the left and right microphones 103 are convolved. These transfer functions are the same as those shown in the conventional example of FIG. 4 and are Hsl2 and Hsr2. Here, by using the transfer functions Hsl2 and Hsr2 from the front direction sound source to the microphones 103 placed on both auricle portions as the transfer functions, only the front direction sound source is detected as a sound source with the same phase, the same level, and flat on the left and right. That is, the transfer functions Hsl2 and Hsr2 function as detection means for the front direction sound source.

[0040] Next, in the second transfer characteristic 406, the transfer function from the front direction sound source of the listener to both ears of the listener is convolved with each output signal. Here, the transfer functions are the same as those shown in FIG. 5 and are Hsl3 and Hsr3. Through the above processing, the original transfer characteristics of the microphone device are canceled, and a conversion is performed to the listener transfer characteristics including the head diffraction signal and further including the transfer function from the front direction sound source to the auricle of the listener. However, here, only the front direction sound source is accurately reproduced, and the effect on sound sources in other directions becomes smaller as the distance from the front direction increases. However, in human hearing, accuracy is required to correctly reproduce sound image localization and sound quality in the front direction, and the auditory effect due to the improvement of the front sound image is significant.

[0041] As described above, in the filter processing unit, a method of adding a head diffraction signal to a front-direction sound source and further giving the transmission characteristics by the direct wave from the sound source to both ears of the listener has been described. Also in the present invention, the in-body transfer functions Hsnl3 and Hsnr3 by the in-body path 55 from the nasal cavity 50 through the nasal cavity 51, the eustachian tube 52, and the tympanic cavity 53 to the eardrum 54 in FIG. 6 can also be added. In the example of FIG. 21(b), an example of the filter processing unit 404 including the in-body transfer functions Hsnl3 and Hsnr3 is shown. The in-body transfer functions Hsnl3 and Hsnr3 are inserted in parallel with the transfer functions Hsl3 and Hsr3 by the out-of-body path from the sound source to both ears of the listener in the second transfer characteristic 407. However, here too, accurate reproduction is only for the front-direction sound source, and the effect of the in-body transfer function for sound sources in other directions becomes smaller as the distance from the front direction increases. In this way, even a binaural sound collection device without a head structure can faithfully collect the propagation of the audio signal from the front-direction sound source of the listener to the eardrum position in a form including the in-body path, and in particular, it is possible to perform highly faithful sound collection and reproduction with headphones for the front-direction sound source.

[0042] FIG. 22 shows a fifth embodiment of the sound collection device according to the present invention. A configuration having a pair of left and right auricle parts 102, a pair of left and right auricle structure parts 100 that hold the auricle parts 102, a connecting part 101 that connects the left and right auricle structure parts at a certain length, and a pair of left and right first microphone parts 103 installed on each of the left and right auricle parts is the same as the conventional example shown in FIG. 2. In the present invention, a signal processing unit 500 that performs signal processing on the output signal of the microphone is provided. Further, a transfer function from the sound source to the microphone is measured, and a measurement unit 505 that stores filter data 507 in the signal processing unit 500 is provided according to the measurement result. FIG. 23 shows the details of the signal processing unit 500. Inside the signal processing unit 500, the input voice signal from the microphone unit 103 is amplified and converted into a digital signal through an amplifier 501 and an A / D converter 502, and then passed to a filter processing unit 504 in a digital signal processing unit 503. The filter processing unit 504 is the same as the filter processing unit 404 in FIG. 21 of the fifth embodiment.

[0043] Next, the details of the measurement unit 505 are shown in FIG. 24. The measurement unit 505 has an insert ear type microphone input unit 506 that inputs the voice signal from an insert ear type microphone 510 that can be attached to both ear holes of the listener, and a speaker output unit 512 that outputs a test signal to an external speaker 511. With the insert ear type microphone 510 attached to the ear hole of the listener, the speaker 511 is placed in the front direction, the test signal is output from the speaker output unit 512, and the test signal is reproduced by the speaker 511, so that the transfer function from the speaker 511, which is the sound source in the front direction, to both ears of the listener can be measured. The measured transfer function is directly substituted into the second transfer characteristics Hsl3 and Hsr3 shown in FIG. 21 in the filter unit 504 through the filter data 507. By providing the measurement unit 505, the second transfer characteristics Hsl3 and Hsr3 can be replaced with the transfer function of any listener, and a sound collection system capable of achieving good front sound source sound collection for any listener can be realized.

[0044] A sixth embodiment of the sound collection device according to the present invention is shown in Fig. 25(a). It consists of a pair of left and right insert ear type microphone units 600 that collect acoustic signals outside the auricle inserted into the left and right ear canals of the listener, and a second microphone 601 that collects voice signals in the middle part between the left and right auricles and reaches the front intermediate point of the listener. Each collected sound signal is input to a signal processing unit 602. The insert ear type microphone 600 is inserted into the left and right ear canals of the listener, for example, as shown in Fig. 25(b). In addition, output signal cables 604 of the same length are provided for the left and right insert ear type microphones 600 inserted into the left and right ear canals, and by installing the second microphone 601 at the connection part 603, the second microphone 601 can be installed at almost the intermediate point between the left and right auricles. The configuration in the signal processing unit 602 is the same as that of the signal processing unit 110 in Fig. 8 of the first embodiment, and its effect is also the same as that of the first embodiment.

[0045] Fig. 26 shows another form of the sixth embodiment of the sound collection device according to the present invention. It consists of a pair of left and right insert ear type microphone units 700 that collect acoustic signals outside the auricle inserted into the left and right ear canals of the listener, and a signal processing unit 701. The configuration in the signal processing device 701 is the same as that of the signal processing unit 150 in Fig. 15 of the second embodiment, and its effect is also the same as that of the second embodiment.

[0046] A seventh embodiment of the sound collection device according to the present invention is shown in Fig. 27. In this embodiment, the connection part 14 in the overall system diagram (a) is configured to be able to expand and contract. The connection part details (b) show an example of the structure inside the connection part. The connection part 14 consists of a thick pipe connection part 802, a thin pipe connection part 803, and a spring part 801 that is inside the thick pipe connection part 802 and connects one end inside the thick pipe and the thin pipe connection part. The thick pipe connection part 802 is connected to one auricle structure part 13, and the thin pipe connection part 803 is connected to the other auricle structure part 13. The spring 801 has a natural length in the most contracted state, and the distance between the left and right auricle structure parts 13 is minimized in the initial state. Further, a rubber ring-shaped stopper part 804 for fixing the connection part length in the extended state is provided on the thin pipe connection part 803.

[0047] Next, Fig. 28 shows the differences in transmission characteristics due to the differences in the inter-aural length. In both cases, the audio signal from the front-direction sound source is input as a same-phase and same-level signal by the microphones placed at El and Er. However, due to the auricle structure, the transmission characteristics Hsl4, Hsl4 and Hsl5, Hsl5 are different according to the incident angle of the sound wave, and particularly a difference occurs in the frequency characteristics. Also, for sound sources other than the front-direction sound source, the arrival time difference from the sound source to the left and right auricle parts is also different, and particularly the difference with respect to the sound image localization position becomes large. Therefore, by making the length of the connecting part variable and adapting it to the inter-aural length of the listener, it becomes possible to improve the sound image localization and the sound quality not only from the front-direction sound source but also from sound sources in all directions. Furthermore, the present invention can further improve the accuracy with respect to the front sound source by adding the transmission characteristics from the nose part to the eardrum described in the first embodiment and the second embodiment. In this case, since the distance from the nose part to the eardrum position also changes according to the length of the inter-aural length, it is also possible to give more appropriate transmission characteristics according to the set inter-aural length by changing the delay amounts of the filter part delayers 118 and 119 shown in Fig. 9.

[0048] Also, another application example of the present invention is shown in Fig. 29. Here, it is used as a holder for holding a recording device such as a smartphone between the ears. There are many smartphones having a size close to the average inter-aural length of humans, which is 150 mm. Fig. 29 shows a state in which an external recording device 810 such as a wide-width smartphone and a narrow external recording device 811 are respectively attached to this sound collection device. Each of the external recording devices 810 and 811 is held by the restoring force of a spring part 801 provided in the connecting part 14. Here, since it is held by the restoring force of the spring part 801, the stopper part 804 is not used. With such a configuration, it becomes possible to use an external recording device such as a smartphone integrally with this sound collection device, and furthermore, by adding the external recording device between the ears, it can also contribute to the improvement of the through-hole phenomenon in which the sound wave from the front-direction sound source passes through the connecting part.

Industrial Applicability

[0049] The technology disclosed in this specification has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions to the embodiments without departing from the gist of the technology disclosed in this specification.

[0050] Although the present invention has been described as a sound source sound collection system, the present microphone system can be applied as a data measurement system for a virtual sound source reproduction system that measures the transfer function from the sound source to the microphone output signal and reproduces the measured transfer function with a signal processing device to reproduce any sound source placed at the sound source position in headphone reproduction.

[0051] Although the present invention has been described as a sound source sound collection system, in a virtual sound source reproduction system that measures the transfer function from the sound source to both ears of the listener and reproduces the measured transfer function with a signal processing device to reproduce any sound source placed at the sound source position in headphone reproduction, the in-body path filter disclosed in the present microphone system can be applied as a correction means for the measured transfer function data.

Explanation of Reference Numerals

[0052] 1 Nose part, 10 Auricle part, 11 Head part, 12 Microphone part, 13 Auricle structure part, 14 Connecting part, 50 Nostril, 51 Nasal cavity, 52 Eustachian tube, 53 Middle ear cavity, 54 Eardrum, 55 Internal body path, 56 Nose part, 100 Auricle structure part, 101 Connecting part, 102 Auricle part, 103 Microphone part, 104 Second microphone, 110 Signal processing part, 111 Filter processing part, 112 Amplifier, 113 A / D converter, 114 Digital signal processing part, 115 Addition part, 116 Head diffraction part filter, 117 Internal body path part filter, 118 Delay unit, 119 Delay unit, 120 Attenuator, 121 Attenuator, 122 Adder, 150 Signal processing part, 151 Filter processing part, 152 Amplifier, 153 A / D converter, 154 Digital signal processing part, 155 Addition part, 156 Front sound source extraction processing part, 157 FFT processing, 158 Phase comparison processing, 159 Level comparison processing, 160 Inverse FFT processing, 200 Detachable part, 201 Tip part, 202 Ear hole part, 203 Surface distance, 300 Detachable part, 301 Tip part, 302 Ear hole part, 303 Surface distance, 400 Signal processing part, 401 Amplifier, 402 A / D converter, 403 Digital signal processing part, 404 Filter processing part, 405 First transmission characteristic, 406 Second transmission characteristic, 407 Second transmission characteristic, 500 Signal processing part, 501 Amplifier, 502 A / D converter, 503 Digital signal processing part, 504 Filter processing part, 505 Measurement part, 506 Insert ear type microphone input part, 507 Filter data, 510 Insert ear type microphone, 511 External speaker, 512 Speaker output part, 513 Voice output part, 600 Insert ear type microphone, 601 Second microphone, 602 Signal processing part, 603 Connecting part, 604 Output cable, 700 Insert ear type microphone, 701 Signal processing part, 801 Spring part, 802 Thick pipe connecting part, 803 Thin pipe connecting part, 804 Stopper part, 810 External recorder, 811 External recorder

Claims

1. A sound collection system comprising a pair of left and right auricle structures including auricle parts simulating the left and right auricles of a human being, a connecting part that holds and connects the pair of left and right auricle structures at a fixed distance, and a pair of left and right microphones installed on the pair of left and right auricle structures, A sound collection system comprising: a detection means for detecting an audio signal transmitted from a front direction sound source to the midpoint between the left and right pair of microphones; a filter processing section for adding a transmission characteristic from the human nose to the eardrum to the detected audio signal; and a synthesis processing section for synthesizing the output signal of the filter processing section with the output signals of the left and right pair of microphones.

2. 2. The sound collection system according to claim 1, wherein the detection means is a second microphone provided at a midpoint between the pair of left and right microphones.

3. 2. The sound collection system according to claim 1, wherein the detection means is a front sound source extraction processing section that extracts a front direction sound source signal from the output signals of the pair of left and right microphones.

4. The sound collection system of claim 1, wherein the detection means is a semi-cylindrical structure that can be attached and detached between the pair of left and right auricle structures, has a height greater than the vertical length of the auricles, detects sound waves coming from the front direction by diffraction on its surface, and inputs the sound waves into the pair of left and right microphones; the filter processing unit is the semi-cylindrical structure, and when attached, the distance from the front tip to the ear canal position in the auricles is 120 mm or more and 200 mm or less, and adds the transmission characteristics due to surface diffraction propagation as an acoustic filter.

5. the detection means is a first transfer characteristic processing unit that detects and outputs a frontal sound source signal as an in-phase, same-level signal for left and right by convolving an inverse of a first transfer characteristic from a frontal sound source to the pair of left and right microphones, the first transfer characteristic being measured in advance, with respect to an input signal from the sound source to the pair of left and right microphones; The sound collection system of claim 1, wherein the filter processing unit is a second transfer characteristic processing unit that convolves the transfer characteristic from the sound source to the listener's both ears and the combined transfer characteristic from the listener's nose to the both ears with respect to the detected front direction sound source signal, and the synthesis processing unit is a second transfer characteristic processing unit that convolves the second transfer characteristic with respect to a pair of sound source signals input from microphones and synthesizes them.

6. The sound collection system of claim 5 further comprises a measurement unit comprising an external microphone unit that can be attached to and detached from the left and right ear canals of a listener, a speaker output unit that outputs a test signal to an external speaker, and a measurement means that measures the transfer characteristics from the external speaker to the external microphone, and the second transfer characteristic is determined by the measurement unit.

7. 7. The sound collection system according to claim 1, wherein the transfer characteristics from the human nose to the eardrum include at least the transfer characteristics due to diffracted waves on the face surface from the nose to the ear canal.

8. The sound collection system according to any one of claims 1 to 6, characterized in that the transfer characteristics from the human nose to the eardrum include transfer characteristics within the human body from at least the human nostrils to the eardrum via the nasal cavity, the auditory tube, and the tympanic cavity.

9. In a sound collection system using a pair of in-ear microphones inserted into the left and right ear canals of a human, A sound collection system comprising: a detection means for detecting an audio signal transmitted from a sound source in the front direction to the midpoint of the left and right ear canals; a filter processing section for adding a transmission characteristic from the human nose to the eardrum to the detected audio signal; and a synthesis processing section for synthesizing the output signal of the filter processing section with the output signals of the left and right microphones.

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