Sound recording device

Abstract

To provide a sound recording device that enables recording, including the transmission characteristics from the nose to both ears for a sound source in the front direction, even for a binaural sound recording device without a head structure, thereby improving the quality of the front directional sound image and sound quality.SOLUTION: A sound recording system includes first microphone units 103 placed at both right and left ears, a second microphone 104 placed at the midpoint between both the ears, a filter processing unit 111 that adds the transmission characteristics from the human nose to the eardrum to the audio signal propagating from the frontal sound source detected by the second microphone 104 to the nose, and a signal processing unit 110 including a digital signal processing unit 114 including a summing unit 115 that synthesizes the left and right microphone output signals from the microphone units 103 and the output signal from the filter processing unit 111.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] A binaural sound collection device is a sound collection system that uses microphones that mimic the structure of the left and right human ears. When the collected stereo sound is listened to using stereo headphones, the system allows the listener to hear sound that is more realistic, as if they were actually there, compared to stereo sound collection using a typical two-channel microphone.

[0003] Conventional binaural sound collection devices with pinnae can be roughly divided into two types depending on their shape. The first type is a so-called dummy head microphone, which has not only pinnae 10 on which a pair of left and right microphone units 12 are installed, but also a head 11, i.e., a human head structure such as a nose and face, as shown in Figure 1. In a microphone of this shape, sound propagation from a sound source S in the front direction is divided into propagation of direct waves Hsl from the sound source S to both ears El and Er, as shown in Figure 3. 1、 Since it picks up not only Hsr1 but also Hsdl1 and Hsdr1 propagated by diffracted waves from sound source S that hit nose 1, are diffracted by the nose and face surface, and reach both ears, it is possible to pick up sound with high accuracy, especially from the front direction. On the other hand, since it has a head 11, its shape is large and its shape imitates a real head, which may cause negative emotions such as creepiness to some people, and it has the problem of being difficult to handle.

[0004] Next, Figure 2 shows a second shape. This second shape has only the pinna structure 13 including the pinna 10, and does not have any head structures corresponding to the nose or face. The left and right pinna structures 13 are connected by a connecting part 14, such as a rod-shaped or rectangular case. In this case, by making the connecting part 14 smaller, it is possible to achieve a lightweight and compact design, and it is easy to store and handle. However, as shown in Figure 4, sound propagation from a sound source S in the front direction is dominated by direct waves Hsl2 and Hsr2 from the sound source S to the pinna microphones. The sound wave Hc that reaches the center between the two ears passes almost unchanged. The diffracted waves Hsdl2 and Hsdr2 from the face and other components are relatively low in level or have characteristics completely different from the transmission characteristics of diffraction by the head structure. This results in poor sound pickup accuracy, particularly from a sound source in the front direction, and the sound image in the front direction becomes blurred, resulting in a so-called "hollow sound" phenomenon in sound image localization.

[0005] A common problem with these conventional systems, particularly with regard to the collection of sound sources in the front, is that the localization position, quality, and even timbre of the sound image differ from what a listener hears with their own ears. This difference from what a listener hears with their own ears is related to several factors. For example, one factor is that the binaural sound collection device that collects the sound differs from the shape of the listener's ears or head. Another factor is that the sound collection system of a conventional binaural sound collection device does not cover all of the acoustic propagation paths through which a listener perceives sound.

[0006] To address the issue of binaural sound collection devices and listeners with different ear or head shapes, one method is to attach microphones directly to the listener's ear canals or near their ears. With this method, the transfer characteristics from the sound source to both ears reflect the listener's characteristics directly. Therefore, when the same listener listens to the collected sound using headphones, the sound image localization and sound quality reproduction are excellent, and sound that is close to what the listener actually hears can be captured. However, this method of attaching microphones to the listener themselves has the problem that the microphone position usually moves with head movement, making it difficult to collect sound in a fixed direction and prone to noise contamination due to the listener's movement.

[0007] The latter path of sound waves from a sound source to a listener's ears does not necessarily have to be external to the human body, i.e., through the head and the outside of the pinna, and then to the eardrum. For example, in a type of sound propagation called cartilage conduction, sound vibrations on the skin near the pinna are transmitted to the cartilage near the pinna, propagate through the body, and then radiate from the wall of the ear canal to reach the eardrum. Furthermore, the nostrils are connected to the eardrum through the nasal cavity, Eustachian tube, and tympanic cavity, and sound waves from the nostrils also contribute to perception. Thus, when humans perceive sound, there are various sound propagation paths that propagate within the human body. In particular, the acoustic input signal from the nostrils is primarily sound waves from a frontal sound source, which is thought to significantly affect the reproducibility of a frontal sound source. Recently, with the COVID-19 pandemic and other factors, there has been an increased need to wear masks, and the effects of sound propagation within the human body are being recognized anew. It has been pointed out that wearing a mask reduces sound clarity and the sense of sound localization compared to not wearing a mask, and the propagation of acoustic signals input through the nostrils is thought to be one of the factors, along with differences in nose shape due to masks.

[0008] However, in conventional binaural sound collection systems, the propagation of such acoustic signals inside the human body was not taken into consideration. For example, Fig. 3 shows the sound propagation path from the sound source S to the microphone unit 12 in the conventional example of Fig. 1. In this example, the sound pressure Pl1Pr1 at both ears is a composite characteristic of the transfer characteristics of the direct wave from the sound source S to both ears, Hsl1Hsr1, and the transfer characteristics of the diffracted wave from the sound source S hitting the nose unit 1, diffracted by the nose and face surface, and reaching the ears, Hsdl1 and Hsdr1. The sound signals actually collected by the microphones placed on the left and right pinna structures are as follows: (Number 1) Pl1 = (Hsl1 + Hsc1) × S (1) (Number 2) Pr1= (Hsr1+Hsc1)×S (2) In this example, the acoustic signal from the frontal sound source S can include diffracted components from the face and nose 1 of the head structure in the picked-up signal, and in particular, the pickup of the frontal sound source is improved compared to the conventional example shown in Figure 2. However, this method only picks up the propagation of acoustic signals outside the human body from the sound source to both ears, and does not pick up acoustic signals that enter through the nostrils and propagate through the body, so it still cannot be said to be sufficient in terms of reproducing sound sources in the front direction.

[0009] Furthermore, in the sound propagation path from sound source S to the microphone in the conventional example of Figure 2 shown in Figure 4, if the transfer characteristics from the frontal sound source S to the microphone are Hsl2 and Hsr2, not only will the acoustic signal that enters from the nostrils and propagates through the body be picked up, but the diffracted waves at the connecting part will also be hardly picked up, and the sound pressure Pl2Pr2 at the binaural microphone will be approximately expressed by the following equation. (Number 3) Pl2 = (Hsl2) × S (3) (Number 4) Pr2= (Hsr2)×S (4) In other words, the sound wave Hc emitted from the sound source S to the midpoint between the left and right microphones of both ears is hardly picked up by the microphones placed on both ears, which causes problems with reproducibility such as a dropout phenomenon of a frontal sound source. Summary of the Invention [Problem to be solved by the invention]

[0010] As mentioned above, binaural sound collection devices with a shape that simulates not only the pinna structure but also the head structure can collect sound from a sound source in the front direction, including diffracted signals from the head, but the inclusion of a head structure not only increases the size and weight of the device, but also makes it difficult to handle due to its spherical shape.Furthermore, because the shape resembles a real head, there is the issue that it may create negative feelings such as an eeriness when used in an audience.

[0011] On the other hand, in binaural sound collection devices that only reproduce the pinna structure and do not have a head structure, when collecting sound from a sound source in the front direction, they can faithfully collect the direct waves from the sound source to both ears, but they cannot faithfully collect the diffracted waves from the face and nose, resulting in a problem where the sound image in the front direction becomes blurred, causing a so-called ``hollow center'' phenomenon in sound image localization.

[0012] Another method is to attach microphones directly to the ear canals or near the ears of the listener, rather than using a fixed binaural sound collection device. This method provides good sound image and sound quality reproduction when the listener listens to the collected sound through headphones, but it has problems such as the microphone position moving with head movement, making it difficult to collect sound from a fixed direction for long periods of time, and noise caused by the listener's movement being easily mixed in.

[0013] Furthermore, in any type of conventional binaural sound collection device or in the method of directly attaching microphones to the pinna of the listener, the microphone placed on the pinna only picks up sound signals that propagate from outside the human body to the eardrum, and does not pick up sound signals that propagate inside the human body, particularly from the nostrils through the nasal cavity, Eustachian tube, and tympanic cavity to the eardrum. As a result, there is a problem that sound signals due to propagation inside the human body are lost, and clarity, sound image localization, and tone quality are impaired, especially when collecting and reproducing sound from a sound source in the front. [Means for solving the problem]

[0014] In order to solve the above problem, the sound collection system according to the invention of claim 1 comprises: 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 connects and holds the left and right auricle structures at a fixed distance, and a pair of left and right microphones installed on the left and right auricle structures, This system is characterized by comprising a detection means for detecting an audio signal transmitted from a front direction sound source to the midpoint between the left and right of the microphone, 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. This method allows for sound pickup that reflects the transmission characteristics of the propagation path from the sound source to the microphones placed on the left and right ears, as well as the propagation path from the sound source through the nose to the eardrums, both inside and outside the head. This improves the clarity of sound pickup from the front and the sense of sound localization.

[0015] The sound collection system according to claim 2 is as follows: The detecting means is a second microphone provided at the midpoint between the pair of left and right microphones. This method allows accurate detection of the sound signal from the sound source to the nose 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, it is possible to improve the clarity of sound pickup from the front direction and the sense of sound image localization.

[0016] The sound collection system according to claim 3 is as follows: The detecting means is characterized in that it is a median plane sound source extraction process that extracts a median plane direction sound source signal from the output signals of the pair of left and right microphones. This method makes it possible to accurately detect the sound signal from the sound source in the front direction to the nose, even without a second microphone. By using filter processing to reflect the transmission characteristics of the propagation path inside and outside the head from the nose to the eardrum, it is possible to improve the clarity of sound pickup from the front direction and the sense of sound image localization.

[0017] The sound collection system according to claim 4 of the present invention is as follows: The detection means and the filter processing unit are semi-cylindrical structures that can be attached and detached between the pair of left and right auricle structures, have a height greater than the vertical length of the auricle, and when attached, the distance from the front tip to the ear canal position in the auricle is 120 mm or more and 200 mm or less. According to this method, by adding a semi-cylindrical structure or a spherical truncated structure to detect sound sources in the front direction and by filtering the sound as an acoustic circuit, the transmission characteristics due to diffraction outside the head from the nose to the eardrum can be reflected, and the clarity of sound pickup from the front direction and the sense of sound image localization can be improved.

[0018] The sound collection system according to claim 5 of the present invention is as follows: the detection means detects a first transfer characteristic from a front direction sound source to the pair of left and right microphones, The filter processing unit is characterized in that it is a difference between the first transfer characteristic and a second transfer characteristic from a sound source in a direction in front of the listener to the left and right ear canals of the listener. According to this method, the audio signals input from the front direction to a pair of left and right microphones are detected as signals with the same phase and level by dividing them by the transfer characteristics from the front direction sound source to the pair of left and right microphones, which have been measured in advance. Furthermore, by performing a filter process that gives the transfer characteristics from the sound source in front of the listener to both ears via the nose, accurate sound pickup is possible that gives the transfer characteristics to both ears of the listener for the front direction sound source, and this can improve the clarity of sound pickup from the front direction and the sense of sound image localization in particular.

[0019] The sound collection system according to the invention of claim 6 is The system is characterized in that a measurement unit is provided which comprises an external microphone unit which can be attached to and detached from the left and right ear canals of the listener, an audio output unit which outputs a test signal to an external speaker, and a measurement means which measures the transfer characteristic from the external speaker to the external microphone, and the second transfer characteristic is determined by the measurement unit. This method makes it possible to change the transmission characteristics from a sound source directly in front of the listener to both ears within the sound collection system, thereby providing a sound collection system that improves the clarity of sound collection from a sound source directly in front of the listener and the sense of sound image positioning for any listener.

[0020] The sound collection system according to the invention of claim 7 comprises the following components: The transmission characteristics from the human nose to the eardrum include at least the transmission characteristics due to diffracted waves on the face surface from the nose to the ear canal. According to this method, even if the binaural sound collection device does not have a diffraction section due to the head as an acoustic circuit, it is possible to collect sound from a binaural sound collection device with a head structure, or from a sound source in the front direction equivalent to that of a listener, making it possible to provide a sound collection system that improves the clarity of sound collection from the front direction and the sense of sound image positioning.

[0021] The sound collection system according to the invention of claim 8 is the sound collection system according to claims 1 to 6. 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 Eustachian tube, and the tympanic cavity. This method makes it possible to collect sound signals propagating through the body from the nostrils, providing a sound collection system that improves the clarity of sound collected from the front and the sense of sound image positioning.

[0022] In addition, the sound collection system according to the invention of claim 9 is In a sound collection system using a pair of in-ear microphones inserted into the left and right ear canals of a human, This system is characterized by comprising a detection means for detecting an audio signal transmitted from a frontal sound source to the midpoint between 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. With this method, the propagation path outside the head from the sound source to the microphones placed on the listener's left and right earlobes is the listener's actual head, which not only enables optimal sound collection for the listener, but also makes it possible to collect sound that reflects the transmission characteristics of the internal and external propagation path from the frontal sound source through the nose to the eardrum, thereby improving the clarity of sound collection from the front and the sense of sound image positioning in particular.

[0023] In addition, the sound collection system according to the invention of claim 10 is A sound collection device 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 left and right auricle structures, and a pair of left and right microphones installed on the left and right auricle structures, The connecting part is characterized by being expandable. This method allows the microphone's inter-ear length to be adjusted to match the listener's inter-ear length, bringing the transfer function from a frontal sound source to both ears closer together, improving the clarity of sound pickup from the frontal sound source and the sense of sound image positioning. [Effects of the Invention]

[0024] According to the present invention, even a fixed microphone system that has only an auricle and no head structure can collect sound that reflects the transfer characteristics of a microphone device with a head structure or a real head. In addition to sound pickup via the propagation path outside the head from the sound source to the microphones placed in the left and right auricle structures, it is also possible to pick up sound that reflects the transmission characteristics of the internal body path from the sound source through the nostrils, Eustachian tubes, and tympanic cavity to the eardrum, thereby improving the clarity of sound pickup from the front and the sense of sound image positioning in particular. [Brief explanation of the drawings]

[0025] [Figure 1] This is a conventional binaural sound pickup device with a head and auricle. [Figure 2] This is a conventional binaural sound pickup device that has only the pinna. [Figure 3] This shows the sound propagation path of a conventional binaural sound pickup device that has a head and auricles. [Figure 4] 1 shows the sound propagation path of a conventional binaural sound pickup device that has only the pinna. [Figure 5] This is the sound propagation path from a sound source in front to the eardrum. [Figure 6] This is the internal path that sound takes from the nostrils to the eardrum. [Figure 7] 1 is an overall system diagram of a sound collection system according to a first embodiment of the present invention. [Figure 8] 1 shows a signal processing unit of a sound collection system according to a first embodiment of the present invention. [Figure 9] 3 shows a filter processing unit of the sound collection system according to the first embodiment of the present invention. [Figure 10] 3 shows head diffraction characteristics of the sound collection system according to the first embodiment of the present invention. [Figure 11] 3 shows the propagation characteristics within the body of the sound collection system according to the first embodiment of the present invention. [Figure 12] 3 is an example of peak filter characteristics of the sound collection system according to the first embodiment of the present invention. [Figure 13]3 is an example of bandpass filter characteristics of the sound collection system according to the first embodiment of the present invention. [Figure 14] FIG. 10 is an overall system diagram of a sound collection system according to a second embodiment of the present invention. [Figure 15] 10 is a signal processing unit of a sound collection system according to a second embodiment of the present invention. [Figure 16] 10 is a diagram showing a front direction sound source extraction unit of a sound collection system according to a second embodiment of the present invention. [Figure 17] FIG. 10A is a three-sided view of a sound collection system according to a third embodiment of the present invention, showing the state in which a detachable part is not attached, and FIG. 10B is a perspective view of the detachable part and a three-sided view showing the state in which the detachable part is attached. [Figure 18] FIG. 10A is a three-sided view of a sound collection system according to a third embodiment of the present invention, showing the state in which the detachable part is not attached, and FIG. 10B is a schematic view of the detachable part and a three-sided view showing the state in which the detachable part is attached. [Figure 19] FIG. 10 is an overall system diagram of a sound collection system according to a fourth embodiment of the present invention. [Figure 20] 10 is a signal processing unit of a sound collection system according to a fourth embodiment of the present invention. [Figure 21] In the sound collection system according to the fourth embodiment of the present invention, (a) is a filter processing unit that does not include an internal propagation unit, and (b) is a filter processing unit that includes an internal propagation unit. [Figure 22] FIG. 10 is an overall system diagram of a sound collection system according to a fifth embodiment of the present invention. [Figure 23] 10 shows a signal processing unit of a sound collection system according to a fifth embodiment of the present invention. [Figure 24] 10 is a diagram showing a measurement section of a sound collection system according to a fifth embodiment of the present invention. [Figure 25] 10A is a diagram showing the entire sound collection system according to the sixth embodiment of the present invention, and FIG. 10B is a diagram showing a state in which an in-ear microphone is fitted in an ear canal. [Figure 26] FIG. 10(a) is a diagram showing another sound collection system according to a sixth embodiment of the present invention, and FIG. 10(b) is a diagram showing a state in which an in-ear microphone is fitted in an ear canal. [Figure 27] 13A is an overall view of a sound collection device according to a seventh embodiment of the present invention, and FIG. 13B is a detailed view of a connecting portion. [Figure 28] FIG. 13 is a diagram showing the transfer characteristics when the interaural distance is long (a) and when the interaural distance is short (b) according to the seventh embodiment of the present invention. [Figure 29] FIG. 10(a) is a diagram showing the connection part when a large external recorder is attached, and FIG. 10(b) is a diagram showing the connection part when a small external recorder is attached, according to the seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of a 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 Figure 4, in a conventional binaural sound pickup system without a head structure, the sound propagation path from a sound source in the front direction to the microphones placed in the pinnae parts is mainly due to direct waves Hsl2 and Hsr2 from the sound source to both ears, and the sound wave Hc heading towards the center between the ears passes directly through the center between the ears and is hardly picked up, or even if it is picked up, the level is low and completely different from the diffracted waves from the listener's head. Therefore, if the transfer functions of the direct waves are Hsl2 and Hsr2, the sound pressure Pl2Pr2 at the binaural microphone parts 12 placed in the left and right pinnae parts from the front sound source S can be approximately expressed by the following equation: (Number 5) Pl2 = (Hsl2) × S (5) (Number 6) Pr2= (Hsr2)×S (6)

[0027] However, as shown in Figure 5, sound propagation from an actual sound source in the front direction to the position of the listener's eardrums is not only a direct wave (a) Hsl3, Hsr3, but also includes head-diffracted waves (b) Hsdl3, Hsdr3 from the listener's nose 56 as an important element, and there is also an internal body path 55 (c) Hsnr3, Hsnr3, as shown in Figure 6, which enters from nostrils 50 in nose 56, passes through nasal cavity 51, Eustachian tube 52, and tympanic cavity 53, and propagates from the inside of eardrum 54. Therefore, in order to improve the clarity and sound image localization of sound picked up from a sound source in the front direction, which are generally considered difficult to reproduce in a binaural sound collection device, it is necessary to further consider the transfer function from nose 56 to the position of the eardrums. In Fig. 5, the left and right transfer functions of the direct wave from the front sound source S are Hsl3 and Hsr 3、 The left-right transfer function due to head diffraction is Hsdl 3、 Hsdr 3、 The left-right transfer function by the internal pathway is Hsnl 3、 If Hsnr3, the left and right sound pressures Pl3Pr3 at the eardrum position are expressed by the following equations. (Number 7) Pl3= (Hsl3+Hsdl3+Hsnl3)×S...(7) (Number 8) Pr3= (Hsr3+Hsdr3+Hsnr3)×S...(8)

[0028] Therefore, in order to achieve sound collection characteristics similar to those of the listener's ears for a frontal sound source using a binaural sound collection device that does not have a head structure, the transfer functions (5) and (6) must be made closer to (7) and (8). In the present invention, for a sound source S in the front direction, not only the direct wave but also the transfer function obtained by combining the transfer functions (Hsdl3 + Hsnl3) and (Hsdr3 + Hsnr3) from the nose 56 to the eardrum 53 is provided, and further, the transfer functions Hsl2 and Hsr2 from the sound source S in the front direction that are inherent to the microphone device are combined into the extracorporeal path transfer function Hsl 3、 Hsr3 or Hsl3+Hsdl including the diffraction part 3、By converting to Hsr3+Hsdr3, it is possible to realize a binaural sound recording system with good forward sound image positioning and sound quality, even if the binaural sound recording device does not have a head structure. [Example]

[0029] FIG. 7 shows a first embodiment of a sound collection system according to the present invention. The configuration is the same as that of the conventional system shown in FIG. 2, with a pair of left and right auricles 102, a pair of left and right auricle structures 100 that hold the auricles 102, a connecting portion 101 that connects the left and right auricle structures at a fixed length, and a pair of left and right first microphones 103 installed on each auricle. The present invention further includes a second microphone 104 located midway between the left and right auricles, and a signal processing portion 110 that processes the output signals of the first and second microphones. The first microphone 103 is normally located at the eardrum deep inside the ear canal. However, since the transfer characteristics of the ear canal are included in the propagation characteristics when sound is reproduced through headphones, it may be located at the entrance of the ear canal, taking into account headphone reproduction. It is assumed that the transfer characteristics from the headphones to the microphones are flat or compensated to be flat.

[0030] Details of signal processing unit 110 in this embodiment are shown in Fig. 8. In Fig. 8, output signals from first microphone units 103 placed on both the left and right ears and second microphone 104 placed midway between the ears are input to signal processing unit 110. Signal processing unit 110 comprises amplifier 112 that amplifies each microphone signal, A / D converter 113 that converts the amplified analog signal into a digital signal, and digital signal processing unit 114 that performs digital signal processing on the input microphone signal, and further comprises filter processing unit 111 that performs filter processing on the second microphone signal and adder unit 115 that adds the filter processing unit output to each of the left and right first microphone signals.

[0031] The details of the filter processing unit 111 are shown in Figure 9. The filter processing unit 111 is composed of a head diffraction filter 116, an internal path filter 117, delays 118 and 119 that apply delay times to the outputs of the filters, attenuators 120 and 121 that adjust the output signal levels of the delays, and an adder 122 that adds the outputs of the attenuators. The head diffraction filter 116 and / or the internal path filter 117 may be included. Furthermore, the head diffraction filter 116 includes a filter that simulates the transfer characteristics of sound diffracted from the nose of a dummy head microphone with a head structure through the face surface to the eardrum. The transfer characteristics from the nose to the eardrum due to diffraction by the head surface can be calculated as a simulation or actual measurement value, representing the difference between the transfer characteristics from the sound source to the positions of both ear canals when a head structure is present and when it is not. An example of the diffraction characteristics calculated in this manner is shown in Figure 10. This characteristic has a peak value around 5kHz to 6kHz, and the level is -20dB to -15dB compared to the direct wave at 1kHz. Therefore, the level of the diffracted wave compared 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, internal path filter 117 represents the transfer characteristics of the internal path filter from the nostrils to the eardrum via the nasal cavity, Eustachian tube, and tympanic cavity. An example of the characteristics is shown in FIG. 11. The characteristics are calculated by measuring a speaker placed at the human nostrils as a sound source and using a microphone placed in the ear canal near the eardrum, or by simulation. In this example, the filter has a 3 kHz to 5 kHz bandpass characteristic with a peak characteristic near 3 kHz. That is, signals in the 3 kHz to 5 kHz band are input to the eardrum from the tympanic cavity side. Therefore, in the filter section, signals that have passed through this bandpass filter are inverted in phase and added in adder 122. The level in attenuator 119 is adjusted using an original sound comparison method or the like. Furthermore, delay devices 118 and 119 add a delay time, for example, a delay time of approximately 150 μs, corresponding to the time difference between the propagation time from the sound source directly to both ears and the propagation time from the sound source via the nose to the eardrum.

[0033] 10 and 11 are provided in the filter unit 111. The filter characteristics are configured by an FIR filter, or by a peak filter or bandpass filter that matches the frequency characteristic shape near the peak frequency as shown in Figures 12 and 13. Here, an example of an internal body path filter is shown. The present invention can also 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 a head diffraction signal at the head for sound waves coming from the front direction. Therefore, since the head diffraction signal is already included in the collected sound data, it is sufficient to use the same configuration as in Fig. 7, and to provide only the internal body path filter 117 in the filter processing unit in Fig. 9. As described above, by adding the transfer characteristics from the nose to the eardrum position to the output signal of the second microphone 104 placed midway between the two ears in the filter processing unit 111 and synthesizing it with the output signals of the pair of first microphones 103 on the left and right, even a binaural sound collection device that does not have a head structure can collect sound with head diffraction and internal body path characteristics for a frontal sound source.

[0034] FIG. 14 shows a second embodiment of the sound collecting device according to the present invention. The configuration is the same as the conventional example shown in Figure 2, with 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 fixed length, and a pair of left and right first microphone parts 103 installed on each of the left and right auricle parts, and is provided with a signal processing part 150 that performs signal processing on the output signal of the microphone part 103. 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. The digital signal processing unit 154 includes a front sound source extraction processing unit 156 that compares the amplitude and phase of the left and right input signals to extract a front direction sound source, and a filter processing unit 151 that adds the transfer characteristics of the propagation path from the nose to the left and right eardrums to the extracted front direction sound source signals.

[0035] The difference from the first embodiment is that instead of collecting the signal from the front direction sound source by the second microphone, the front direction sound source is extracted from the correlation between the left and right signals of the microphone unit 103 placed on the left and right ears. FIG. 16 shows details of the front sound source extraction unit 156. Digital signals from the two left and right microphones 103 are converted into the frequency domain by FFT processing 157. The left and right audio signals converted into the frequency domain are input to phase comparison processing 158 and level comparison processing 159. Here, the input signal from the front direction sound source can be estimated from the phase difference and level difference. From the relationship between the interaural phase difference and level difference from the sound source to the two ears, a sound source from directly in front has approximately the same level and phase on the left and right. For example, if a sound source within a range of ±10° from the front is considered to be in the front direction, from the well-known relationship between the interaural time difference and interaural level difference related to sound image localization, when there is a 10° sound source directional angle difference, the interaural time difference is approximately 50 μsec and the interaural level difference is approximately 3 dB. In this case, the interaural phase difference is approximately 18° at 1 kHz, for example. Therefore, in the phase comparison process 128, for each frequency bin in the frequency domain, signals with a phase difference that can be considered to be in the front direction, for example, a phase difference of within 18° left and right, are extracted, and the level difference of the extracted frequency bin signals is then compared in the level comparison process 129. Here, signals with a level difference of within 3 dB left and right are extracted. By performing inverse FFT processing on the extracted frequency bins in the IFFT unit 160, sound source signals in the front direction can be extracted from the left and right microphone signals. Note that this extraction method extracts sound sources not only in the front direction but also in all directions in the median plane. However, since rear sound sources have lower sensitivity to sound image localization and sound quality than front sound sources, processing median plane sound sources as front sound sources and improving the sound pickup accuracy of the front sound sources has the advantage of improving sound image localization and sound quality.

[0036] In this way, by filtering the front direction sound source signals extracted from the left and right microphone signals using the filter unit 151 in Fig. 15, it is possible to realize a binaural sound collection device with improved front direction localization and timbre. The processing in the filter unit 151 is the same as that in Fig. 9 in the first embodiment.

[0037] Figure 17 shows a third embodiment of a sound collection device according to the present invention. This device differs from the conventional microphone device shown in Figure 2 in that it has a detachable semi-cylindrical structure called a detachable part 200. Figure 17(a) shows the front, top, and side views of the device when not attached, while Figure 17(b) shows the detachable part 200 and the front, top, and side views of the device when attached. As seen in the side view, the detachable part 200 has a height dimension that is at least higher than the pinna, and the surface distance 203 from the tip 201, where sound waves from a front sound source first arrive, to the ear canal part 202 where the microphone is attached is set to between 120 mm and 200 mm, which corresponds to the distribution of distances from the tip of the human nose to the ear canal. By wearing the detachable part 200, sound waves coming from a sound source in front of the microphone device are detected without passing through, at least sound waves arriving from in front of the pinna. Diffraction on the surface of the detachable part adds a transfer function of diffraction propagation to the sound waves, which are then input to both ears. In other words, this structure functions as a detector for detecting sound sources in the front direction, and at the same time, functions as a filter, as the transfer characteristics due to diffraction propagation on the structure surface act as an acoustic filter. As a result, diffracted waves from a sound source in the front direction are picked up, making it possible to improve sound image localization and sound quality.

[0038] In the present invention, the detachable part 200 has been described as a cylindrical structure, but it can also be replaced with a barrel-shaped spherical base or a structure that resembles a human face with a nose, as long as it has a structure that provides the above-mentioned surface distance from the front tip to the ear canal. Furthermore, a second microphone can be provided inside the nose portion to add a function of collecting sound from the internal body passage shown in the first embodiment. Furthermore, by using a detachable structure, it is possible to select a surface distance close to the listener's ears, i.e., a diffraction distance, and it is possible to provide characteristics close to the diffraction characteristics of the listener. Figure 18 shows another example of the present invention. The detachable part 300 has a face mask structure made of a film-like plastic plate, and is attached to both auricles with elastic rubber 301, making it even lighter. By changing the width of the plastic plate, it can be adjusted to match the diffraction distance of the listener.

[0039] FIG. 19 shows a fourth embodiment of the sound collecting device according to the present invention. The configuration, which includes a pair of left and right auricles 102, a pair of left and right auricle structures 100 that hold the auricles 102, a connecting portion 101 that connects the left and right auricle structures at a fixed length, and a pair of left and right first microphone portions 103 installed on each of the left and right auricles, is the same as the conventional example shown in FIG. 2. The present invention includes a signal processing portion 400 that processes the microphone output signal. FIG. 20 shows the details of the signal processing portion 400. In the signal processing portion 400, the audio signal input from the microphone portion 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 portion 404 within the digital signal processing portion 403. FIG. 21 shows the details of the filter processing portion 404. In the example of FIG. 21(a), in the first transfer characteristic 405, the reciprocals 1 / Hsl2 and 1 / Hsr2 of the transfer functions from the front direction sound source of this microphone device to the left and right microphones 103 are convolved with the left and right input signals. These transfer functions are Hsl2 and Hsr2, the same as those shown in the conventional example in Fig. 4. Here, by using the transfer functions Hsl2 and Hsr2 from the front direction sound source to the microphones 103 placed on both pinnae as the transfer functions, only the front direction sound source is detected as a sound source with the same phase, level and flatness on the left and right. In other words, 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 functions from the sound source in front of the listener to both ears of the listener are convoluted 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 conversion is performed to listener transfer characteristics that include head diffraction signals and the transfer function from the sound source in the front to the listener's pinna. However, here, only the sound source in the front direction is accurately reproduced, and the effect on sound sources in other directions becomes smaller the further away from the front direction. However, in human hearing, the accuracy required for correctly reproducing sound image positioning and sound quality is in the front direction, and improving the sound image in the front direction has a significant effect on the auditory sense.

[0041] The above describes a method in which a head-diffracted signal is added to a sound source in the frontal direction in the filter processing section, and furthermore, a transfer characteristic of a direct wave from the sound source to the listener's ears is added. However, in the present invention, it is also possible to add the internal body transfer functions Hsnl3 and Hsnr3 of the internal body path 55 from the nostrils 50 through the nasal cavity 51, the auditory tube 52, and the tympanic cavity 53 to the eardrum 54 in FIG. 6 . The example in FIG. 21( b) shows an example of a filter processing section 404 including the internal body transfer functions Hsnl3 and Hsnr3. The internal body transfer functions Hsnl3 and Hsnr3 are inserted in parallel with the transfer functions Hsl3 and Hsr3 of the external body path from the sound source to the listener's ears in the second transfer characteristic 407. However, even here, only the sound source in the frontal direction is accurately reproduced, and the effect of the internal body transfer functions on sound sources in other directions decreases with distance from the frontal direction. In this way, even a binaural sound collection device that does not have a head structure can faithfully collect the propagation of audio signals from a sound source in front of the listener to the eardrum position, including the path through the body, making it possible to collect sound with high fidelity, especially for sound sources in the front, and play it back through headphones.

[0042] FIG. 22 shows a fifth embodiment of the sound collecting device according to the present invention. The configuration of the present invention, which includes a pair of left and right auricles 102, a pair of left and right auricle structures 100 that hold the auricles 102, a connecting portion 101 that connects the left and right auricle structures at a fixed length, and a pair of left and right first microphone portions 103 installed on each auricle, is the same as the conventional example shown in FIG. 2. The present invention further includes a signal processing portion 500 that processes the microphone output signal, and a measurement portion 505 that measures the transfer function from the sound source to the microphone and stores filter data 507 in the signal processing portion 500 based on the measurement results. FIG. 23 shows the details of the signal processing portion 500. Within the signal processing portion 500, the audio signal input from the microphone portion 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 portion 504 within a digital signal processing portion 503. The filter processing portion 504 is the same as the filter processing portion 404 in the fifth embodiment shown in FIG. 21.

[0043] Next, details of measurement unit 505 are shown in Fig. 24. Measurement unit 505 has an in-ear microphone input unit 506 that inputs an audio signal from in-ear microphone 510 that can be worn in both ear canals of a listener, and a speaker output unit 512 that outputs a test signal to an external speaker 511. By placing speaker 511 in front of a listener who has in-ear microphone 510 worn in their ear canals, outputting the test signal from speaker output unit 512 and reproducing it through speaker 511, it is possible to measure the transfer function from speaker 511, which is a sound source in the front direction, to both ears of the listener. The measured transfer function is passed through filter data 507 and directly substituted into second transfer characteristics Hsl3 and Hsr3 shown in Fig. 21 in filter unit 504. By providing the measuring unit 505, the second transfer characteristics Hsl3 and Hsr3 can be replaced with the transfer functions of any listener, and a sound collection system that can collect good sound from a front sound source 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 comprises a pair of left and right in-ear microphone units 600 that are inserted into the left and right ear canals of the listener to collect acoustic signals from outside the auricles, and a second microphone 601 that is located midway between the left and right auricles to collect audio signals that reach a midpoint in front of the listener. Each collected signal is input to a signal processing unit 602. 25(b), the in-ear microphones 600 are inserted into the left and right ear canals of the listener. By providing output signal cables 604 of the same length to the left and right in-ear microphones 600 inserted into the left and right ear canals and installing a second microphone 601 at a connecting part 603 of the cables, the second microphone 601 can be installed at approximately the midpoint between the left and right auricles. The internal configuration of the signal processing unit 602 is similar to that of the signal processing unit 110 of the first embodiment shown in FIG. 8, and the effects thereof are also similar to those 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 comprises a pair of left and right in-ear microphone units 700 that are inserted into the left and right ear canals of a listener to collect acoustic signals outside the pinna, and a signal processing unit 701. The internal configuration of signal processing unit 701 is the same as that of signal processing unit 150 in Fig. 15 of the second embodiment, and its effects are also the same as those of the second embodiment.

[0046] FIG. 27 shows a seventh embodiment of a sound collection device according to the present invention. In this embodiment, the connecting section 14 in the overall system diagram (a) is configured to be extendable. The connecting section details (b) show an example of the structure within the connecting section. The connecting section 14 comprises a thick pipe connecting section 802, a thin pipe connecting section 803, and a spring section 801 located within the thick pipe connecting section 802 and connecting one end of the thick pipe to the thin pipe connecting section. The thick pipe connecting section 802 connects to one pinna structure section 13, and the thin pipe connecting section 803 connects to the other pinna structure section 13. The spring 801 reaches its natural length when fully compressed, and the distance between the left and right pinna structures 13 is minimized in the initial state. Furthermore, the thin pipe connecting section 803 is provided with a stopper section 804, e.g., a rubber ring, that fixes the length of the connecting section when extended.

[0047] Next, Figure 28 shows the difference in transfer characteristics due to differences in interaural distance. In both cases, audio signals from a frontal sound source are input as in-phase level signals to the microphones placed at El and Er. However, the transfer characteristics Hsl4, Hsl4 and Hsl5, Hsl5 differ depending on the angle of incidence of the sound waves due to the structure of the pinna, resulting in differences in frequency characteristics in particular. Furthermore, for sound sources other than frontal sound sources, the difference in arrival time from the sound source to the left and right pinna also differs, resulting in significant differences in sound image localization position. Therefore, by making the connecting section length variable and adjusting it to the listener's interaural distance, it is possible to improve sound image localization and sound quality not only from frontal sound sources but also from sound sources in all directions. Furthermore, the present invention can further improve accuracy for frontal sound sources by adding the transfer characteristics from the nose to the eardrum, as described in the first and second embodiments. In this case, the distance from the nose to the eardrum position changes depending on the interaural distance, so by changing the delay amount of the filter section delay devices 118 and 119 shown in Figure 9, it is possible to provide a more appropriate transfer characteristic depending on the set interaural distance.

[0048] Another application example of the present invention is shown in Figure 29. Here, a recorder such as a smartphone is used as a holder to hold a recorder between the ears. Many smartphones have dimensions close to the average human ear-to-ear distance of 150 mm. Figure 29 shows two external recorders, such as a wide smartphone 810 and a narrow external recorder 811, attached to the sound collection device. Each external recorder 810 and 811 is held in place by the restoring force of spring 801 attached to connecting portion 14. Because the external recorders are held in place by the restoring force of spring 801, stopper 804 is not used. This configuration allows an external recorder such as a smartphone to be used in conjunction with the sound collection device. Furthermore, placing an external recorder between the ears can help reduce the "blindness" phenomenon, where sound waves from a sound source directly in front of the device pass through the connecting portion. [Industrial Applicability]

[0049] Although the technology disclosed in this specification has been described in detail with reference to specific embodiments, it is obvious that those skilled in the art can modify or substitute the embodiments without departing from the spirit of the technology disclosed in this specification.

[0050] Although the present invention has been described as a sound source pickup system, this microphone system can also be applied as a data measurement system for a virtual sound source reproduction system that reproduces any sound source placed at the sound source position through headphone reproduction by measuring the transfer function from the sound source to the microphone output signal and reproducing the measured transfer function using a signal processing device.

[0051] The present invention has been described as a sound source pickup system, but 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 using a signal processing device to reproduce any sound source placed at the sound source position through headphone reproduction, the internal body path filter disclosed in this microphone system can be applied as a means for correcting the measured transfer function data. [Explanation of symbols]

[0052] 1 nose part, 10 pinna part, 11 head, 12 microphone part, 13 pinna structure part, 14 connection part, 50 nostril, 51 nasal cavity, 52 Eustachian tube, 53 tympanic cavity, 54 tympanic membrane, 55 internal body path, 56 nose part, 100 pinna structure part, 101 connection part, 102 pinna 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 adder part, 116 head diffraction part filter, 117 internal body path part filter, 118 delay, 119 delay, 120 attenuator, 121 attenuator, 122 adder, 150 signal processing part, 151 filter processing part, 152 amplifier, 153 A / D converter, 154 digital signal processing unit, 155 addition unit, 156 front sound source extraction processing unit, 157 FFT processing, 158 phase comparison processing, 159 level comparison processing, 160 inverse FFT processing, 200 detachable unit, 201 tip unit, 202 ear canal unit, 203 surface distance, 300 detachable unit, 301 tip unit, 302 ear canal unit, 303 surface distance, 400 signal processing unit, 401 amplifier, 402 A / D converter, 403 digital signal processing unit, 404 filter processing unit, 405 first transfer characteristic, 406 second transfer characteristic, 407 second transfer characteristic, 500 signal processing unit, 501 amplifier, 502 A / D converter, 503 digital signal processing unit, 504 filter processing unit, 505 measurement unit, 506 in-ear microphone input unit, 507 Filter data, 510 in-ear microphone, 511 external speaker, 512 speaker output section, 513 audio output section, 600 in-ear microphone, 601 second microphone, 602 signal processing section, 603 connection section, 604 output cable, 700 in-ear microphone, 701 signal processing section, 801 spring section, 802 thick pipe connection section, 803 thin pipe connection section, 804 stopper section, 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 connects and holds the left and right auricle structures at a fixed distance, and a pair of left and right microphones installed on the 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 of the microphone; 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.

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 pickup system according to claim 1, wherein the detection means is a front sound source extraction process for extracting 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 and the filter processing unit are semi-cylindrical structures that can be attached and detached between the pair of left and right auricle structure parts, have a height greater than the vertical length of the auricle parts, and when attached, the distance from the front tip to the ear canal position in the auricle parts is 120 mm or more and 200 mm or less.

5. the detection means detects a first transfer characteristic from a front direction sound source to the pair of left and right microphones, 2. The sound collection system according to claim 1, wherein the filter processing section is a difference between the first transfer characteristic and a second transfer characteristic from a sound source in front of the listener to the left and right ear canals of the listener.

6. 6. The sound collection system of claim 5, further comprising 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 wherein 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 frontal sound source to the midpoint between 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.

10. 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 for holding and connecting the left and right auricle structures, and a pair of left and right microphones installed on the left and right auricle structures, This sound pickup system is characterized by its extendable connecting parts.

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