Sound pickup device

Abstract

To enable pickup of clear audio with the effects of vibration suppressed.SOLUTION: A sound pickup device includes a first sound collection unit, a second sound collection unit, and an adder. The first sound collection unit includes a first electro-acoustic transducer connected to one end of a first cable, the second sound collection unit includes a second electro-acoustic transducer connected to one end of a second cable. The first electro-acoustic transducer and the second electro-acoustic transducer are arranged in parallel in opposite directions between one end of the first cable and one end of the second cable. The adder adds a first acoustic signal output from the other end of the first cable and a second acoustic signal output from the other end of the second cable.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application relates to a sound collection device, and more particularly to a technology for collecting clear sound in, for example, an environment where significant noise occurs. [Background technology]

[0002] In recent years, attempts have been made to create content using volumetric capture technology. Volumetric capture technology is a technology that acquires spatial information about an object in three-dimensional space and enables spatial presentation. To acquire video, multiple cameras are placed around the subject to capture the subject, and a three-dimensional model of the subject is generated. Post-processing is then performed on the generated three-dimensional model to realize various presentations. For example, a video is created in which the three-dimensional shape of the subject is observed from a desired viewpoint (Non-Patent Document 1).

[0003] In audio capture, similar to video capture, attempts are being made to capture sound using a microphone array placed around the performer, who is the sound source. The acoustic radiation characteristics of the sound source are obtained based on the captured sound and the placement of each microphone. The obtained acoustic radiation characteristics are then used to consider acoustical effects.

[0004] However, in MetaStudio, noise is generated from cameras and other video equipment, and other devices. Therefore, microphone arrays installed far from the sound source may be subject to relatively high levels of noise. Even if the acoustic radiation characteristics from the sound source can be obtained, it is not guaranteed that the sound emitted from the sound source will be clearly captured. If clear sound can be captured, the accuracy of the acquired acoustic radiation characteristics can be expected to improve.

[0005] In the past, in order to capture clear sound in high noise levels, microphones placed very close to the performers were used. While the sound quality of the audio captured using these microphones was relatively good, the image of the microphone could sometimes appear in the video of the performers. For this reason, recording using microphones placed very close to the performers is not suitable for MetaStudio.

[0006] Furthermore, a method has been proposed for eliminating the image of a microphone reflected in multiple captured images (Non-Patent Document 2). However, this method causes processing delays, making it unsuitable for MetaStudio, which requires real-time processing, and also places a heavy load on the image processing. Another option is to use a shotgun microphone placed so that it is not within the camera's field of view. It has been reported that using a superdirectional shotgun microphone can improve the clarity of sounds picked up from a distance (Non-Patent Document 3). However, even this method is insufficient for capturing sound in a metastudio. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Toshie Misu, "MetaStudio: Capture the Reality of Everything," NHK Giken R&D, No. 190, Summer 2022, pp. 42-49, published August 15, 2022 [Non-patent document 2] Rumsey, Francis, Audio for Cinema, Journal of the Audio Engineering Society, Volume 66, Issue 3, p.182-185, March 19, 2018 [Non-patent document 3] Sasaki, Yo and Ono, Kazuho, ​​Shotgun Microphone with High Directivity by Extra-Long Acoustic Tube and Digital Noise Reduction, Audio Engineering Society Convention 145, Paper 10097, October 7, 2018 [Non-patent document 4] Akihiro Suzuki, Basic Course on Microphone Use (5th Lecture) Practical Examples in Documentaries, Broadcasting Technology, Kenrokukan Publishing, 62 (8), pp.155-162, August 2009 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, in order to clearly capture the sound of sound sources in MetaStudio, it is considered practical to use lavalier microphones that can be stored in the performer's clothing so that they do not appear in the video. However, the lavalier microphone cable can vibrate in the width direction as it attaches to and detaches from the performer's clothing in response to their movements, and in the axial direction as the contact point moves. These vibrations can cause noise (Non-Patent Document 4).

[0009] The embodiments of the present application have been made to solve the above-mentioned problems, and one of the objectives is to provide a microphone that can pick up clear sound with the effects of vibration suppressed. [Means for solving the problem]

[0010] [1] One aspect of this embodiment is a sound collection device comprising a first sound collection unit having a first electro-acoustic transducer connected to one end of a first cable, a second sound collection unit having a second electro-acoustic transducer connected to one end of a second cable, and an adder, wherein the first electro-acoustic transducer and the second electro-acoustic transducer are arranged in parallel in opposite directions at one end of the first cable and one end of the second cable, and the adder adds a first acoustic signal output from the other end of the first cable and a second acoustic signal output from the other end of the second cable. According to the configuration of [1], the main component of the vibration component generated by the vibration of the first cable or the second cable is in opposite phase between the first acoustic signal and the second acoustic signal. In contrast, the signal components from the sound source are in phase between the first acoustic signal and the second acoustic signal picked up by the first electro-acoustic transducer and the second electro-acoustic transducer, which are located close to each other. In the output signal obtained by adding the first acoustic signal and the second acoustic signal, the vibration components are canceled out while the signal components are emphasized. As a result, it is possible to pick up sound coming from the sound source with clear sound quality.

[0011] [2] One aspect of this embodiment is a sound collection device comprising a first sound collection unit having a first electro-acoustic transducer connected to one end of a first cable, a second sound collection unit having a second electro-acoustic transducer connected to one end of a second cable, and a subtractor, wherein the first electro-acoustic transducer and the second electro-acoustic transducer are arranged in parallel with one end of the first cable and one end of the second cable in the same direction, and the subtractor obtains the difference between one of a first acoustic signal output from the other end of the first cable and a second acoustic signal output from the other end of the second cable. According to the configuration of [2], the main component of the vibration component generated by the vibration of the first cable or the second cable is in phase between the first acoustic signal and the second acoustic signal. In contrast, the signal components from the sound source are in phase between the first acoustic signal and the second acoustic signal picked up by the first electro-acoustic transducer and the second electro-acoustic transducer, which are located close to each other. In the output signal obtained by subtracting the first acoustic signal and the second acoustic signal, the vibration components cancel each other out, while a differential component resulting from the difference in the positions of the first electro-acoustic transducer and the second electro-acoustic transducer is obtained. Therefore, the first and second sound pickup units have relatively high sensitivity to sounds arriving from distant directions, making it possible to pick up sounds arriving from those directions with clear sound quality.

[0012] [3] One aspect of this embodiment is the above-mentioned sound collection device, wherein the first electro-acoustic transducer is housed in a first container, the second electro-acoustic transducer is housed in a second container, and a side surface of the first container and a side surface of the second container are joined. According to the configuration of [3], even if irregular vibrations are applied due to the movements of the performer, the first electroacoustic transducer and the second electroacoustic transducer can maintain a stable positional relationship without coming into direct contact with each other.

[0013] [4] One aspect of this embodiment is the sound collection device described above, wherein the first container and the second container may be arranged in parallel and bonded together. According to the configuration of [4], the positional relationship between the first electroacoustic transducer and the second electroacoustic transducer is maintained parallel even when irregular vibrations are applied due to the movements of the performer.

[0014] [5] One aspect of the present embodiment is the above-described sound collection device, wherein the first cable and the second cable may have the same size. According to the configuration of [5], the mechanical characteristics of the first and second cables are similar, so the vibration components propagating through the first and second cables are similar. This reduces the difference in the vibration components contained in the output signal, resulting in clearer sound quality. [Effects of the Invention]

[0015] According to the above configuration, it is possible to pick up clear sound with the influence of vibrations suppressed. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram showing a first configuration example of a sound collection device according to the present embodiment. [Figure 2] 1 is a diagram showing a first configuration example of a microphone capsule according to the present embodiment. FIG. [Figure 3] 1 is a diagram illustrating an example of the configuration of a cable according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a second configuration example of a microphone capsule according to the present embodiment. [Figure 5] 10A and 10B are diagrams illustrating an example of measurement of an acoustic signal in a first measurement pattern. [Figure 6] 10A and 10B are diagrams illustrating an example of measurement of an acoustic signal in a second measurement pattern. [Figure 7] 10A and 10B are diagrams illustrating an example of measurement of an acoustic signal in a third measurement pattern. [Figure 8] FIG. 10 is a diagram showing a measurement system for a second measurement pattern. [Figure 9] FIG. 2 is a diagram showing a second configuration example of the sound collection device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present application will be described with reference to the drawings. First, an outline of this embodiment will be described. FIG. 1 is a diagram showing an example of the configuration of a sound collection device 1 according to this embodiment. The sound collection device 1 includes two sound collection units 10 and 20, an adder 32, and an output interface 34.

[0018] The sound collection device 1 is configured as a lavalier microphone. A lavalier microphone is a small microphone also known as a tie-pin microphone. The sound collection device 1 is typically used with a mounting device (holder clip, not shown) attached. The mounting device is made up of a support (holder) and a fastener (clip) engaged together. The support is pressed against the side of the microphone capsules 11 and 21 provided in the sound collection units 10 and 20, fixing the position and orientation of the microphone capsules 11 and 21. The fastener clamps another member (e.g., clothing) to fix the position of itself and, ultimately, the microphone capsules 11 and 21. A windshield may be attached to the microphone capsules 11 and 21.

[0019] The sound collection unit 10 includes a microphone capsule 11, a cable 12, and a microphone amplifier 18. The microphone capsule 11 includes a transducer 11t (FIG. 2). A transducer (electroacoustic transducer) 11t is connected to one end of the cable 12. The transducer 11t is housed in a case 11c (FIG. 2) of the microphone capsule 11 so that its axial direction, i.e., its longitudinal direction, is oriented along an extension line from one end of the cable 12. Therefore, at one end of the cable 12, the longitudinal direction of the microphone capsule 11 is oriented along the extension direction of the cable 12. The cable 12 transmits the electrical signal output from the transducer 11t to a microphone amplifier 18 as an acoustic signal. A typical length of the cable 12 is about 1 to 4 m.

[0020] The microphone amplifier 18 adjusts the amplitude of the acoustic signal output from the other end of the cable 12 and outputs the amplitude-adjusted acoustic signal to the adder 32. The microphone amplifier 18 has an impedance matching circuit (not shown). The impedance matching circuit converts the electrical impedance of the acoustic signal output from the cable 12 so that it matches the electrical impedance of the electrical signal output to the adder 32.

[0021] The sound collection unit 20 has the same configuration and functions as the sound collection unit 10. That is, the sound collection unit 20 includes a microphone capsule 21, a cable 22, and a microphone amplifier 28. The microphone capsule 21 includes a transducer 21t (not shown). The transducer 21t is connected to one end of the cable 22. The transducer 21t is housed in a case 21c of the microphone capsule 21 so that its axial direction is directed along an extension line from one end of the cable 22 (not shown). The microphone amplifier 28 amplifies the acoustic signal output from the other end of the cable 22 and outputs the amplified acoustic signal to the adder 32. The microphone amplifier 28 has amplification characteristics equivalent to those of the microphone amplifier 18. In this application, the acoustic signals output from the other ends of the cables 12 and 22 may be referred to as the "first acoustic signal" and the "second acoustic signal," respectively.

[0022] The microphone capsules 11 and 21 each have a thin, cylindrical shape with a length greater than a width. The microphone capsules 11 and 21 are mechanically joined at their respective sides. The microphone capsules 11 and 21 are joined via an insulating material that is permeable to mechanical vibrations. For example, an adhesive containing cyanoacrylate as a main component is used to join the microphone capsules 11 and 21. For joining the microphone capsules 11 and 21, a jig for bundling the two capsules, such as a binder, may be used instead of an adhesive. The microphone capsules 11 and 21 are arranged in parallel in opposite directions along the longitudinal direction. One end of the cable 12 connected to the microphone capsule 11 and one end of the cable 22 are oriented in opposing directions.

[0023] The adder 32 adds (mixes) the first acoustic signal output from the sound collection unit 10 and the second acoustic signal output from the sound collection unit 20, and outputs the acoustic signal obtained by the addition to the output interface 34 as an output signal.

[0024] The output interface 34 outputs the output signal from the adder 32 to the outside of the sound collection device 1. The output interface 34 may include a wireless transmitter (not shown) and may be configured as a transmitter, or may include an output plug that is detachable from other devices. The wireless transmitter transmits the amplitude-adjusted electrical signal as radio waves having a predetermined carrier frequency. The wireless transmitter can use a short-range wireless communication method specified in, for example, IEEE802.15.1 to transmit the electrical signal.

[0025] Next, a description will be given of an example configuration of the microphone capsule 11. The microphone capsule 21 (FIG. 1) has a shape and configuration similar to those of the microphone capsule 11. The following description will be used to cite the configuration of the microphone capsule 21. FIG. 2 is a diagram showing an example of the configuration of microphone capsule 11. Microphone capsule 11 includes transducer 11t and case 11c. An inner chamber covered with an insulator is formed on the inner surface of case 11c. Transducer 11t is housed in the inner chamber. Transducer 11t converts vibrations of the surrounding air into an electric signal and transmits the obtained electric signal to cable 12 as an acoustic signal. The operating principle of transducer 11t may be any. A typical microphone capsule 11 has a diameter of 2.5 to 10 mm and a length of about 12 to 30 mm.

[0026] However, the transducer 11t illustrated in FIG. 2 is configured as a back electret capacitor based on the electret capacitor system. The back electret capacitor includes a diaphragm (vibration membrane) 11d and a fixed electrode 11b that face each other via a spacer 11s. The diaphragm 11d is a thin film made of a conductor such as metal. The periphery of the diaphragm 11d is supported by a case 11c. The case 11c has an opening 11e at one end. Therefore, sound waves arriving from a sound source enter the case 11c through the opening 11e. The diaphragm 11d vibrates in response to changes in air pressure over time caused by the sound waves entering through the opening 11e. The fixed electrode 11b is made of a charged polymer film and is fixed to the case 11c. The diaphragm 11d serves as a movable electrode, and a DC voltage (e.g., 44 to 52 V) is applied between the two electrodes due to the effect of the charge on the fixed electrode. The voltage between the electrodes fluctuates according to the amplitude of diaphragm 11d, and an electrical signal having the fluctuating voltage is generated as an acoustic signal. Note that, although the main surface of diaphragm 11d is arranged parallel to the longitudinal direction of microphone capsule 11 in the example of Fig. 2, it may be arranged in a direction perpendicular to the longitudinal direction of microphone capsule 11.

[0027] Next, an example of the configuration of cable 12 will be described. Cable 22 (FIG. 1) has a configuration similar to that of cable 12. In other words, the dimensions of cables 12 and 22, i.e., the length, width, and thickness of each layer, are the same. Therefore, cables 12 and 22 have equivalent mechanical properties. The following description of cable 22 is used for reference. FIG. 3 is a diagram showing an example of the configuration of cable 12. Cable 12 includes a core 12a, an insulating layer 12i, a shield 12s, and a covering material (sheath) 12c, which are stacked in this order. Core 12a is a conductor that transmits acoustic signals. Core 12a is made of a conductor such as copper or aluminum. Insulating layer 12i is a layer made of an insulator that covers the periphery of core 12a. The material of insulating layer 12i is a pressure-resistant insulator such as vinyl chloride or polyethylene.

[0028] The shield 12s is a layer made of a conductor that covers the periphery of the insulating layer 12i. The shield 12s shields the core 12a from electromagnetic waves coming from the outside and suppresses radiation of electromagnetic waves generated by electrical signals flowing through the core 12a. The shield 12s functions as a reference potential line by being electrically connected to a potential reference point. The shield 12s is made of a conductor such as copper or aluminum. The covering material 12c is a layer made of an insulator that covers the periphery of the shield 12s. The covering material 12c is made of an insulator that has high resistance to bending fatigue, such as polyvinyl chloride or polyethylene. The diameter of a typical cable 12 is approximately 1.4 to 4.2 mm, the diameter of the core 12a is approximately 0.2 to 0.6 mm, and the thickness of the insulating layer 12i and the shield 12s are each approximately 0.2 to 0.6 mm.

[0029] The above description has been given with reference to an example in which the side of the case 11c (FIG. 2) housing the transducer 11t is joined to the side of the case 21c (not shown) housing the transducer 21t, but this is not limiting. As illustrated in FIG. 4, the case 11c may be configured to house another transducer 21t in addition to the transducer 11t. In this case, the case 21c is omitted, and the transducer 11t and the transducer 21t are housed in parallel and facing in opposite directions in the single case 11c. Here, one end of the cable 12 and one end of the cable 22 are arranged facing in opposite directions with respect to the axial direction of the case 11c or the transducers 11t and 21t. The case 11c is attached to the performer's clothing using an attachment.

[0030] When the sound collection device 1 is attached to the clothing of the performer who is the user, the cables 12 and 22 come into contact with the clothing. The performer's movements cause widthwise vibrations 14 and 24 and axial vibrations 15 and 25 of the cables 12 and 22, respectively, between the clothing and the cables 12 and 22. The axial component of the vibrations generated in the cables 12 and 22 is more dominant than the widthwise component. The sensitivity of the transducers 11t and 21t to the vibrations generated in the cases 11c and 21c also tends to be higher for the axial component than for the widthwise component of the cases 11c and 21c.

[0031] The cases 11c and 21c are arranged in opposite directions relative to the longitudinal direction, and therefore, the vibration components detected by the transducers 11t and 21t housed in the cases 11c and 21c are dominated by components that are in opposite phase to each other. On the other hand, the transducers 11t and 21t are installed close to each other. The distance between the transducers 11t and 21t is typically set so that the distance between the openings 11e and 21e through which sound waves arrive from the sound source is 1 to 2 cm or less. Therefore, air pressure waves radiated from the sound source arrive at the transducers 11t and 21t in phase as sound. Therefore, in the output signal obtained by adding the first acoustic signal and the second acoustic signal, noise components caused by vibration cancel each other out, and the signal components representing sound are relatively emphasized.

[0032] Next, a description will be given of an example of measuring an acoustic signal using the sound collection device 1. The applicant measured a first acoustic signal and a second acoustic signal for each of the following three measurement patterns. Pattern 1: The experimenter rubbed the side of cable 12 with his / her hand, and no sound was presented from the sound source. Pattern 2: The side of the cable 12 is brought into contact with the side of the turntable 56 that rotates at a constant speed, and no sound is presented from the sound source (see FIG. 8). Pattern 3: Without applying vibration to the cable 12, a measurement sweep signal was presented to the microphone capsule 11 from a speaker placed in front of the microphone capsule 11. The front direction of the microphone capsule 11 is the longitudinal direction in which it is not connected to the cable 12, i.e., the direction in which the microphone capsule 21 and the cable 22 are connected. In the example of FIG. 1, pattern 3 corresponds to the case in which a speaker is placed to the right of the microphone capsule 11. For comparison, a measurement sweep sound was presented to a standalone microphone capsule 11 not connected to the microphone capsule 21 from a speaker placed in front of it. Similarly, a sweep sound was presented to a standalone microphone capsule 21 from a speaker placed in front of it.

[0033] In the measurements, a first acoustic signal (Mic. 10) obtained from sound collection unit 10 and a second acoustic signal (Mic. 20) obtained from sound collection unit 20 were recorded. For patterns 1 and 2, the first acoustic signal and the second acoustic signal, as well as the sum signal and difference signal, were evaluated. The sum signal corresponds to the signal obtained by adding the first acoustic signal and the second acoustic signal (Mic. 10 + Mic. 20). The difference signal corresponds to the signal obtained by subtracting the second acoustic signal from the first acoustic signal (Mic. 10 - Mic. 20). For pattern 3, the sum signal of the first acoustic signal and the second acoustic signal (Mic. 10 + Mic. 20) was evaluated, as were the first acoustic signal and the second acoustic signal (Mic. 10 and Mic. 20) obtained by recording using individual microphone capsules 11 and 21, respectively.

[0034] Next, the measurement results will be described. FIG. 5 shows an example of measurement in Pattern 1. In FIG. 5, the vertical axis indicates relative level (unit: dB) and the horizontal axis indicates frequency (unit: Hz). The higher the frequency, the closer the level of the sum signal is to the level of the first acoustic signal or the second acoustic signal, and the lower the frequency, the greater the difference between the level of the first acoustic signal or the second acoustic signal. Specifically, in frequency bands higher than 4 kHz, the level of the sum signal is equivalent to the level of the first acoustic signal or the second acoustic signal, and in frequency bands lower than 2 kHz, the level of the sum signal is approximately 10 dB lower than the level of the first acoustic signal or the second acoustic signal. The level of the difference signal is higher than the levels of the first acoustic signal and the second acoustic signal over the entire frequency band from 200 Hz to 10 kHz.

[0035] FIG. 6 shows an example of measurements made in Pattern 2. In FIG. 6 as well, in the low frequency band below 4 kHz, the level of the sum signal tends to approach the level of the first acoustic signal or the second acoustic signal as the frequency increases, and the difference between the level of the sum signal and the level of the first acoustic signal or the second acoustic signal tends to increase as the frequency decreases. Specifically, in the frequency band above 4 kHz, the level of the sum signal is equivalent to the level of the first acoustic signal or the second acoustic signal, but in the frequency band below 2 kHz, the level of the sum signal is approximately 10 dB or more lower than the level of the first acoustic signal or the second acoustic signal. The level of the difference signal is higher than the levels of the first acoustic signal and the second acoustic signal across the entire frequency band from 200 Hz to 10 kHz.

[0036] The measurement examples in Figures 5 and 6 confirm that, among the vibration components generated in cables 12 and 22, low frequency components below 4 kHz are recorded in antiphase between sound pickup units 10 and 20, and are canceled out by adding the first acoustic signal and the second acoustic signal.

[0037] FIG. 7 shows a measurement example for Pattern 3. However, the sum signal is shown at a 6 dB reduction across the entire frequency range. The difference signal is omitted in FIG. 7. According to FIG. 7, the first acoustic signal recorded by microphone capsule 11 alone, the second acoustic signal recorded by microphone capsule 21 alone, and the sum signal of the first and second acoustic signals obtained by sound collection device 1 all have equivalent frequency characteristics. Over the entire frequency band from 200 Hz to 10 kHz, the level difference between the sum signal of the first and second acoustic signals (after a 6 dB reduction), the first acoustic signal recorded by microphone capsule 11 alone, and the second acoustic signal recorded by microphone capsule 21 alone was all less than 1 dB. This indicates that there is an extremely small difference between the frequency characteristics of the sum signal obtained from sound collection device 1 and the frequency characteristics of the signal components contained in the first acoustic signal and the second acoustic signal obtained by sound collection units 10 and 20 alone.

[0038] The applicant installed speakers on the side and rear sides of the microphone capsule 11 and recorded the sum signal of the first acoustic signal and the second acoustic signal in the same manner as in Pattern 3, and also recorded the first acoustic signal and the second acoustic signal from the microphone capsule 11 and the microphone capsule 21 alone. The first acoustic signal and the sum signal of the second acoustic signal recorded from the sound collection device 1 when the sound source is installed on the side or rear side of the microphone capsule 11, the first acoustic signal recorded from the microphone capsule 11 alone, and the second acoustic signal recorded from the microphone capsule 21 alone all have frequency characteristics similar to those of Pattern 3 (not shown). This indicates that in Pattern 3, the sum signal of the first acoustic signal and the second acoustic signal obtained from the transducers 11t and 21t, which are sufficiently closer than the wavelength, mainly contains signal components, and there is no significant difference in sound quality between the first acoustic signal and the second acoustic signal recorded individually from the transducers 11t and 21t.

[0039] As described above, the sound collection device 1 of this embodiment comprises a first sound collection unit (e.g., sound collection unit 10) having a first electroacoustic transducer (e.g., transducer 11t) connected to one end of a first cable (e.g., cable 12), a second sound collection unit (e.g., sound collection unit 20) having a second electroacoustic transducer (e.g., transducer 21t) connected to one end of a second cable (e.g., cable 22), and an adder 32. The first electro-acoustic transducer and the second electro-acoustic transducer are arranged in parallel with one end of a first cable and one end of a second cable in opposite directions, and an adder 32 adds a first acoustic signal output from the other end of the first cable and a second acoustic signal output from the other end of the second cable.

[0040] With this configuration, the main component of the vibration component generated by the vibration of the first cable or the second cable is out of phase with the first acoustic signal and the second acoustic signal. In contrast, the signal components from the sound source are in phase with the first acoustic signal and the second acoustic signal picked up by the first electro-acoustic transducer and the second electro-acoustic transducer, which are located close to each other. In the output signal obtained by adding the first acoustic signal and the second acoustic signal, the vibration components are canceled out while the signal components are emphasized. As a result, sound coming from the sound source can be picked up with clear sound quality.

[0041] Alternatively, the first electroacoustic transducer may be housed in a first container (e.g., case 11c), the second electroacoustic transducer may be housed in a second container (e.g., case 21c), and the side surfaces of the first container and the second container may be joined together. With this configuration, even if irregular vibrations are applied due to the movements of the performer, the first electroacoustic transducer and the second electroacoustic transducer can maintain a stable positional relationship without coming into direct contact with each other.

[0042] The first container and the second container may also be arranged in parallel and bonded together. With this configuration, the positional relationship between the first and second electroacoustic transducers is maintained parallel even when irregular vibrations are applied due to the movements of the performer. Furthermore, the first cable and the second cable may have the same dimensions (for example, width and length). With this configuration, the mechanical characteristics of the first and second cables are similar, so the vibration components propagating through the first and second cables are similar, reducing the difference in vibration components contained in the output signal and resulting in clearer sound quality.

[0043] 9, the first container (case 11c in the example of FIG. 9) that houses the first sound collection unit and the second container (case 21c in the example of FIG. 9) that houses the second collection unit may be joined together while being arranged in the same direction. The first container and the second container do not have to be perfectly parallel, and may be offset in the axial direction of the transducers 11t and 21t. In the example of FIG. 9, the axial offset between the opening 11e and the opening 21e is, for example, about 1 cm. The sound collection device 1 also includes a subtractor 36 instead of the adder 32. The subtractor 36 outputs the difference between the first acoustic signal and the second acoustic signal as an output signal to the output interface 34. The subtractor 36 illustrated in FIG. 9 subtracts the second acoustic signal from the first acoustic signal. In this case, the vibration components contained in the first acoustic signal and the second acoustic signal are in phase, and therefore, by taking the difference between the first acoustic signal and the second acoustic signal, the vibration components cancel each other out. On the other hand, signal components from the sound source propagating as pressure waves are collected as the differential component between the sound waves arriving at opening 11e and the sound waves arriving at opening 21e. In other words, the sound collection device 1 functions as a pressure gradient microphone as a whole. Therefore, the sensitivity to sounds arriving from the axial direction of the first and second containers, which is approximately the direction in which the first and second containers are separated, can be relatively increased. In this case, by mounting the sound collection device 1 with the axial direction of the first and second containers facing the performer's mouth, clear sound can be collected. In the example of Figure 9, since the sound collection device 1 is configured as a pressure gradient microphone, the output signal from subtractor 36 contains amplitude characteristics proportional to frequency. Furthermore, when the sound collection device 1 functioning as a pressure gradient microphone is installed near the sound source, the proximity effect adds amplitude characteristics inversely proportional to frequency to the output signal in relatively low frequency bands. To avoid or suppress these effects, the sound collection device 1 may be provided with a filtering circuit (not shown) for correcting the frequency characteristics of the differential signal obtained by the subtractor 36, and the output signal from the filtering circuit may be output to the output interface 34.

[0044] In the above description, the transducers 11t, 21t provided in the microphone capsules 11, 21 are condenser microphones based on the electret condenser system, but this is not limiting. The transducers 11t, 21t may be microphones based on other systems, such as dynamic microphones. A dynamic microphone does not require the application of a DC voltage such as a phantom voltage from a phantom power supply.

[0045] Although the present embodiment has been described above with reference to the drawings, the specific configuration is not limited to the above. Various design modifications can be made to the above embodiment without departing from the spirit of the present invention. [Explanation of symbols]

[0046] 1...sound collection device, 10, 20...sound collection unit, 11, 21...microphone capsule, 11b, 21b...fixed pole, 11c, 21c...case, 11d, 21d...diaphragm, 11e, 21e...opening, 11t, 21t...transducer, 12, 22...cable, 12a, 22a...core wire, 12c, 22c...coating material, 12i, 22i...insulating layer, 12s, 22s...shield, 18, 28...microphone amplifier, 32...adder, 34...output interface, 36...subtractor, 56...turntable

Claims

1. a first sound collection unit having a first electroacoustic transducer connected to one end of a first cable; a second sound collecting unit having a second electroacoustic transducer connected to one end of a second cable; an adder; The first electro-acoustic transducer and the second electro-acoustic transducer are arranged in parallel with one end of the first cable and one end of the second cable in opposite directions, The adder A first acoustic signal output from the other end of the first cable and a second acoustic signal output from the other end of the second cable are added together. Sound pickup device.

2. a first sound collection unit having a first electroacoustic transducer connected to one end of a first cable; a second sound collecting unit having a second electroacoustic transducer connected to one end of a second cable; a subtractor; The first electro-acoustic transducer and the second electro-acoustic transducer are arranged in parallel with one end of the first cable and one end of the second cable facing in the same direction, The subtractor A difference between a first acoustic signal output from the other end of the first cable and a second acoustic signal output from the other end of the second cable is obtained. Sound pickup device.

3. the first electroacoustic transducer is housed in a first container; the second electroacoustic transducer is housed in a second enclosure; The side surface of the first container and the side surface of the second container are joined together. The sound pickup device according to claim 1 or 2.

4. The first container and the second container are arranged in parallel and bonded together. The sound pickup device according to claim 3.

5. The first cable and the second cable have the same dimensions. The sound pickup device according to claim 1 or 2.

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