Microphone

Abstract

To provide a microphone for collecting clear sound in which influence of rubbing or vibration is suppressed.SOLUTION: A microphone 20 includes a microphone capsule 21, a cable 22, and a microphone amplifier 28. The microphone capsule 21 converts mechanical vibration into an electric signal. The cable 22 connects the microphone capsule 21 to one end, and has a high impedance unit 36 having higher mechanical impedance than other section in the section within a predetermined range from the one end. The cable 22 transmits the electric signal, and includes a base line 23 covered with a first covering material made of an insulator and a cushioning material that is externally fitted to the first covering material in a section within a predetermined range at least from the one end and has elasticity more than that of the first covering material. The cable may include a second covering material that covers at least the cushioning material and has a surface smoother than the first covering material so as to be distributed in a longitudinal direction of the cable.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present application relates to a microphone, and more particularly to a technique for picking up clear audio without the microphone being photographed in, for example, an environment where significant noise occurs. [Background technology]

[0002] Recently, a volumetric capture technology has been proposed in Meta Studio. In this technology, a three-dimensional model of a subject is generated by placing multiple cameras so as to surround the subject and photographing the subject. Post-processing of the generated three-dimensional model enables various visual effects. For example, a video in which the subject is observed from a desired viewpoint is produced (Non-Patent Document 1). In the volumetric capture at Metastudio, we are trying to collect sound using microphone arrays placed around the performer, who is the sound source, in the same way as with cameras. The acoustic radiation characteristics of the sound source are analyzed based on the collected sound and the placement of each microphone, and various acoustic effects are being considered based on the analyzed acoustic radiation characteristics.

[0003] In Meta Studio, noise is generated by cameras and other video equipment and other equipment. Therefore, a microphone array installed far from the sound source may be mixed with high levels of noise from the equipment. Even if the acoustic radiation characteristics from the sound source can be obtained, it is not necessarily the case that the sound emitted from the sound source is clearly captured. If clear sound can be captured, the accuracy of the obtained acoustic radiation characteristics can be improved. In the past, in order to capture clear sound in high noise levels, microphones were placed close to the performers, who were the sound sources. Although the quality of the sound captured using these microphones was relatively good, the image of the microphones could sometimes appear in the video of the performers. For this reason, this method of capturing sound may not be suitable for recording in a metastudio.

[0004] Also, a method has been proposed for erasing the reflected microphone image from multiple captured images (Non-Patent Document 2). However, this method causes a processing delay, making it unsuitable for MetaStudio, which requires real-time processing, and also places a heavy load on the image processing. Furthermore, sound collection using a shotgun microphone installed so as not to be included in the field of view of the camera is also possible. It has been reported that a certain degree of effectiveness can be obtained when using a superdirectional shotgun microphone to collect sound from a distance from the sound source (Non-Patent Document 3). However, even this method is insufficient for collecting sound in a metastudio. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Toshie Misu, "MetaStudio" captures the entire feeling of realism, NHK Giken R&D, No. 190, Summer 2022, p. 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), p.155-162, August 2009 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, in order to clearly pick up the sound of the sound source in the Meta Studio, it is practical to use a lavalier microphone that can be stored in the performer's clothing so that it does not appear in the video. However, the microphone may be subjected to vibrations caused by contact between the performer's clothing and the microphone in response to the performer's movements, and friction caused by the movement of the contact position. These vibrations and frictions may cause noise (Non-Patent Document 4).

[0007] The embodiments of the present application have been made to solve the above-mentioned problems, and one of the objectives of the present invention is to provide a microphone that can pick up clear sound while suppressing the effects of friction or vibration. [Means for solving the problem]

[0008] [1] One aspect of this embodiment is a microphone comprising an electro-acoustic transducer that converts mechanical vibrations into an electrical signal, and a cable that connects the electro-acoustic transducer to one end, the cable having a section within a predetermined range from the one end that has a higher mechanical impedance than other sections. According to the configuration of [1], pressure waves caused by vibration or friction in other sections of the cable are reflected at the boundary with the section with higher mechanical impedance, and are suppressed from being transmitted to the electro-acoustic transducer. Since the noise components caused by vibration or friction are reduced in the electrical signal recorded by the electro-acoustic transducer, it is possible to record clear sound with the effects of friction or vibration suppressed.

[0009] [2] One aspect of this embodiment is the microphone described above, wherein the cable may be wound around an axis in a direction intersecting with the longitudinal direction in the section. According to the configuration of [2], the winding of the cable prevents pressure waves caused by vibration or friction in other sections from traveling in a straight line, thereby suppressing the transmission of noise components caused by vibration or friction to the electro-acoustic transducer.

[0010] [3] One aspect of this embodiment is the microphone described above, wherein a part of the cable may be connected to another part of the cable in the section via a connector having a higher mechanical impedance than the cable. According to the configuration of [3], the connector blocks pressure waves caused by vibration or friction in other sections, thereby suppressing the transmission of noise components caused by vibration or friction to the electro-acoustic transducer.

[0011] [4] One aspect of this embodiment is the microphone described above, comprising: an electro-acoustic transducer that converts mechanical vibrations into an electrical signal; and a cable connected to one end of the electro-acoustic transducer, wherein the cable comprises a base line that transmits the electrical signal and is covered with a first covering material made of an insulator; and a cushioning material that is more elastic than the first covering material and that is fitted over the first covering material at least in a section within a predetermined range from the one end. A second covering material that covers at least the cushioning material and has a smoother surface than the first covering material is provided and distributed in the longitudinal direction of the cable. According to the configuration of [4], friction caused by contact with the second covering material that covers the cable is reduced, so pressure waves caused by vibration or friction are suppressed. In addition, pressure changes are mitigated by the buffer material, so the transmission of pressure waves caused by vibration or friction to the electroacoustic transducer is suppressed. Noise components caused by vibration or friction are reduced in the electrical signal recorded by the electroacoustic transducer, making it possible to record clear audio with the effects of vibration or friction suppressed.

[0012] [5] One aspect of this embodiment is the microphone described above, wherein the cable further has the cushioning material in a second section within a predetermined range from the other end, and the second covering material may continuously cover the side of the cable. According to the configuration of [5], the second covering material is stably supported by multiple cushioning materials at different positions, and friction caused by contact with the second covering material at the contact position with the cable is reduced or eliminated. Therefore, pressure waves caused by vibration or friction are more reliably suppressed.

[0013] [6] One aspect of this embodiment is the microphone described above, wherein the cable includes a plurality of the cushioning materials distributed in the longitudinal direction of the cable, and the second covering material is divided into sections for each of the cushioning materials and covers each of the cushioning materials. According to the configuration of [6], the cable is provided with second covering materials that cover each of the multiple buffer materials. Pressure waves generated in some of the second covering materials do not directly propagate to other second covering materials or buffer materials. This more reliably suppresses the propagation of pressure waves caused by vibration or friction to the electroacoustic transducer.

[0014] [7] One aspect of this embodiment is the microphone described above, wherein in a third section that is closer to the electro-acoustic transducer than the first section, the baseline may have a portion having a higher mechanical impedance than the other sections. According to the configuration of [7], pressure waves caused by vibration or friction in other sections of the baseline are reflected at the boundary with the third section, and are prevented from being transmitted to the electroacoustic transducer. Therefore, the noise components caused by vibration or friction in the electrical signal recorded by the electroacoustic transducer can be further reduced. Effect of the Invention

[0015] According to the above configuration, it is possible to pick up clear sound while suppressing the effects of friction or vibration. [Brief description of the drawings]

[0016] [Figure 1] 1 is a configuration diagram showing an example of the external configuration of a microphone according to a first embodiment. [Diagram 2] 4 is a configuration diagram showing another example of the external configuration of the microphone according to the first embodiment. FIG. [Diagram 3]10 is a diagram showing an example of the external configuration of a microphone according to a second embodiment. FIG. [Figure 4] FIG. 11 is a plan view illustrating an example of a high impedance portion according to the second embodiment. [Diagram 5] 13 is a side view showing an example of a high impedance section according to the second embodiment. FIG. [Figure 6] FIG. 11 is a configuration diagram showing another example of the high impedance section according to the second embodiment. [Figure 7] FIG. 1 is a perspective view showing an example of the configuration of a microphone capsule according to an embodiment of the present application. [Figure 8] FIG. 2 is a cross-sectional view showing an example of the configuration of a base line according to an embodiment of the present application. [Figure 9] FIG. 11 is a diagram showing an example of the external configuration of a microphone according to a modified example of the present application. [Figure 10] FIG. 13 is a diagram showing frequency characteristics of an audio signal recorded in a preliminary experiment. [Figure 11] FIG. 1 is a diagram showing an experimental system used in a vibration experiment. [Figure 12] FIG. 1 shows an experimental system used in a rubbing experiment. [Figure 13] FIG. 13 is a diagram showing a part of the measurement results in a vibration experiment. [Figure 14] FIG. 11 is a diagram showing another part of the measurement results in the vibration experiment. [Figure 15] FIG. 13 is a diagram showing some of the measurement results in a rubbing experiment. [Figure 16] FIG. 13 is a diagram showing another part of the measurement results in the rubbing experiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] First Embodiment Hereinafter, the embodiments of the present application will be described with reference to the drawings. First, an overview of the first embodiment will be described. FIG. 1 is a configuration diagram showing an example of the external configuration of a microphone 20 according to this embodiment. The microphone 20 is configured as a lavalier microphone. A lavalier microphone is a small microphone also called a tie-pin microphone. The microphone 20 includes a microphone capsule 21, a cable 22, and a microphone amplifier 28. A typical microphone capsule 21 has a diameter of 2.5 to 10 mm and a length of about 12 to 30 mm.

[0018] In the example of FIG. 1, the case of the microphone capsule 21 has an elongated cylindrical shape whose length is longer than its diameter. The microphone 20 is usually used with an attachment (holder clip, not shown) attached. The attachment is formed by engaging a support (holder) with a fastener (clip). The support is pressed against the side of the microphone capsule 21 to fix the position and orientation of the microphone capsule 21. The fastener clamps another member (e.g., clothing) to fix the position of itself and, ultimately, the microphone capsule 21. One end of the cable 22 is connected to the base end of the microphone capsule 21. A windshield may be attached to the tip of the microphone capsule 21.

[0019] The microphone capsule 21 includes a transducer 21t and a case 21c. An inner chamber covered with an insulator is formed on the inner surface of the case 21c. The transducer 21t (FIG. 7) is stored in the inner chamber. The transducer 21t converts vibrations in the surrounding air into an electric signal corresponding to the vibrations, and transmits the obtained electric signal to the cable 22. The transducer 21t may operate on any principle.

[0020] The transducer 21t illustrated in FIG. 7 is configured as a back electret capacitor based on the electret capacitor method. The back electret capacitor includes a diaphragm (vibration membrane) 21d and a fixed pole 21b facing each other via a spacer 21s. The diaphragm 21d is a thin film made of a conductor such as metal. The periphery of the diaphragm 21d is supported by a case 21c. Therefore, the diaphragm 21d vibrates according to the time change in air pressure that constitutes the incoming sound wave. The fixed pole 21b is made of a polymer film having an electric charge and is fixed to the case 21c. The diaphragm 21d serves as a movable pole, and a direct current voltage (for example, 44 to 52 V) is applied between both poles due to the effect of the electric charge of the fixed pole. The voltage between both poles fluctuates according to the amplitude of the diaphragm 21d, and an electric signal having the fluctuated voltage is generated as an audio signal. In the example of FIG. 7, the main surface of diaphragm 21d is disposed parallel to the longitudinal direction of microphone capsule 21, but may be disposed in a direction perpendicular to the longitudinal direction of microphone capsule 21.

[0021] Returning to Fig. 1, cable 22 transmits an electrical signal supplied from transducer 21t housed in microphone capsule 21 to microphone amplifier 28. One end of cable 22 is connected to microphone capsule 21, and the other end of cable 22 is connected to microphone amplifier 28. A typical length of cable 22 is about 1 to 4 m.

[0022] The microphone amplifier 28 adjusts the electrical signal input from the cable 22 according to a predetermined gain, and outputs the amplitude-adjusted electrical signal to another device. The microphone amplifier 28 has an impedance matching circuit (not shown). The impedance matching circuit converts the electrical impedance of the electrical signal input from the cable 22 so that it matches the electrical impedance of the electrical signal output from the microphone amplifier 28 to another device. The microphone amplifier 28 may include a wireless transmitter (not shown) and may be configured as a transmitter. The wireless transmitter transmits an electric signal with an adjusted amplitude as a radio wave having a predetermined carrier frequency. The wireless transmitter may use a short-distance wireless communication method, such as that specified in IEEE802.15.1, for transmitting the electric signal.

[0023] In the case where a capacitor-type transducer 21t other than the electret capacitor type as exemplified in Fig. 7 is employed, the microphone amplifier 28 may include a phantom power supply (not shown). The phantom power supply generates a phantom voltage between two terminals and applies it to both poles of the transducer 21t. The two terminals of the phantom power supply are electrically connected to the core 23a and the shield 23s (Fig. 8) at the other end of the cable 22. The core 23a and the shield 23s are electrically connected to the diaphragm 21d and the fixed pole 21b of the transducer 21t, respectively.

[0024] Next, the noise components caused by contact with the cable 22 will be described. When the microphone 20 is worn while surrounded by clothes, a bag, and other objects, the movement of the performer who is the sound source may cause the cable 22 to come into contact with other objects, or the contact position may move while the contact continues. The cable 22 generates one or both of vibrations 24 caused by contact with other objects and friction 25 caused by the movement of the contact position. Pressure waves caused by the generated vibrations 24 and friction 25 are propagated to the transducer 21t (FIG. 7) stored in the microphone capsule 21 via the cable 22. The transducer 21t detects the vibrations caused by the arriving pressure waves as noise components. Therefore, the noise components are mixed into the audio signal of the collected sound. The cable 22 according to this embodiment has the configuration described below, thereby suppressing the propagation of pressure waves caused by the vibrations 24 or friction 25 to the microphone capsule 21.

[0025] Next, a configuration example of the cable 22 according to this embodiment will be described. The cable 22 includes a base line 23, a buffer material 26, and a second covering material 27. The base line 23 outputs an audio signal input from the microphone capsule 21 to a microphone amplifier 28. As illustrated in FIG. 8, the base line 23 includes a core wire 23a, an insulating layer 23i, a shield 23s, and a first covering material (sheath) 23c, which are superimposed in this order. The core wire 23a is a conductor that transmits an audio signal. The core wire 23a is made of a conductor such as copper or aluminum. The insulating layer 23i is a layer made of an insulator that covers the periphery of the core wire 23a. The material of the insulating layer 23i is an insulator having pressure resistance such as vinyl chloride or polyethylene.

[0026] The shield 23s is a layer made of a conductor that covers the periphery of the insulating layer 23i. The shield 23s blocks electromagnetic waves coming from the outside to the core 23a and suppresses the radiation of electromagnetic waves generated by an electric signal flowing through the core 23a. The shield 23s can function as a reference potential line by being electrically connected to a reference point of potential. The material of the shield 23s is made of a conductor such as copper or aluminum. The first covering material 23c forms a layer made of an insulator that covers the periphery of the shield 23s. The material of the first covering material 23c is an insulator that has high resistance to bending fatigue, such as polyvinyl chloride or polyethylene.

[0027] A buffer material 26 is fitted around the base line 23 covered with the first covering material 23c at least in a section close to one end within a predetermined range. In the example of FIG. 1, two buffer materials 26-1 and 26-2 are circumscribed on the side of the cable 22 at a position close to one end within a predetermined range and a position close to the other end within a predetermined range. The buffer material 26 is made of an insulator having greater elasticity than the first covering material. Here, "elastic" means that the elastic modulus is low, that is, the amount of deformation caused by a certain external force is large, and the buffer material has the property of returning to its original shape when the external force is released. The material of the buffer material 26 is, for example, synthetic rubber having insulating properties such as styrene butadiene rubber and silicone rubber.

[0028] In addition, the base line 23 and the buffer material 26 are covered with the second covering material 27 so as to be distributed between both ends of the cable 22, including the section where the buffer material 26 is fitted. In the example of FIG. 1, the entire side of the cable 22, including the buffer materials 26-1 and 26-2 and the section where they are not fitted, is covered with the second covering material 27. From another perspective, the base line 23 is supported on the inner surface of the second covering material 27 via the buffer materials 26-1 and 26-2. As the second covering material 27, a pipe made of an insulator with a smoother surface than the first covering material is used. A material with a high surface smoothness is generally less susceptible to plastic deformation and has a high elastic modulus. The material of the second covering material 27 is, for example, an insulator having pressure resistance and abrasion resistance, such as polyamide or polyimide.

[0029] This configuration suppresses rubbing 25 caused by contact with the side surface of cable 22. In addition, vibration 24 caused by pressure applied to the side surface of cable 22 and displacement caused by rubbing 25 are mitigated by buffer material 26. This suppresses transmission of pressure waves caused by vibration 24 and rubbing 25 to transducer 21t. This reduces the noise components caused by vibration 24 or rubbing 25 and detected by transducer 21t. Typically, the diameter of the base wire 23 is about 1.4 to 4.2 mm, the diameter of the core wire 23a is about 0.2 to 0.6 mm, the thickness of the insulating layer 23i, the thickness of the shield 23s, and the thickness of the first covering material 23c are each about 0.2 mm to 0.6 mm. The thickness of the buffer material 26 is about 1 to 3 mm, and the thickness of the second covering material 27 is about 0.5 to 1.5 mm.

[0030] In the microphone 20 illustrated in FIG. 1, two buffer materials 26-1 and 26-2 are arranged at both ends of the cable 22, but the number n of buffer materials 26 may be three or more. The n buffer materials 26-1 to 26-n may be arranged at different positions between both ends of the base line 23 and fitted around the base line 23. A gap is provided between adjacent buffer materials 26-i and 26-i+1 (i is an integer between 1 and n-1) so that they do not contact each other. This prevents a pressure wave applied to a specific buffer material 26-i from directly propagating to the adjacent buffer material 26-(i+1). This reduces the noise components carried by the pressure waves arriving at the transducer 21t.

[0031] In the example of FIG. 1, the second covering material 27 covers the base line 23 collectively between both ends of the cable 22, but may be divided into n second covering materials 27-1 to 27-n and distributed. In the microphone 20 illustrated in FIG. 2, n buffer materials 26-1 to 26-n are distributed at different positions between both ends of the base line 23 and fitted around the base line 23. The second covering material 27 is divided into individual buffer materials 26, and the divided second covering materials 27-1 to 27-n cover the corresponding buffer materials 26-1 to 26-n, respectively. A gap is provided between adjacent second covering materials 27-i and 27-(i+1) so that they do not contact each other. This prevents a pressure wave caused by vibration 24 or friction 25 generated in a part of the second covering material 27-i from directly propagating to the adjacent second covering material 27-(i+1). This in turn reduces the noise components carried by the pressure waves arriving at the transducer 21t.

[0032] The configuration and composition of each of the buffer materials 26-1 to 26-n and the second covering materials 27-1 to 27-n are the same as those of the buffer material 26 and the second covering material 27 illustrated in FIG. 1, except for their lengths. Here, "length" refers to the dimension in the longitudinal direction of the cable 22. In the example of FIG. 2, the length of the buffer material 26-i and the length of the corresponding second covering material 27-i are approximately equal. Similarly, the interval between the buffer materials 26-i and 26-(i+1) and the interval between the corresponding second covering materials 27-i and 27-(i+1) are approximately equal.

[0033] The lengths of the n buffer materials 26-1 to 26-n and the intervals between adjacent buffer materials 26-i and 26-(i+1) may not be constant, but may be set randomly according to a pseudorandom number sequence. This makes the distribution of mechanical impedance in cable 22 spatially irregular, thereby making it possible to avoid the occurrence of standing waves (natural vibrations). The corners of the end faces of the second coating materials 27-1 to 27-n may be chamfered to be rounded (R chamfering). The larger the radius of curvature of the end faces, the more preferable. The radius of curvature of the end faces may be set equal to the thickness of the second coating material 27-i, for example. This radius of curvature corresponds to the maximum value. By removing sharp parts, friction with an object that comes into contact with the end face of the second coating material 27-i can be reduced, and noise components due to rubbing can be reduced.

[0034] <Second embodiment> Next, a second embodiment will be described. In the description of this embodiment, differences from the first embodiment will be mainly described, and the description of the microphone 20 according to the first embodiment will be used unless otherwise specified. FIG. 3 is a diagram showing an example of the external configuration of the microphone 20 according to this embodiment. The microphone 20 includes a microphone capsule 21, a cable 22, and a microphone amplifier 28. The cable 22 includes a base line 23. The base line 23 has a section within a predetermined range from one end thereof, in which the mechanical impedance is higher than in other sections (hereinafter, may be referred to as a "high impedance section"). Therefore, pressure waves due to vibration 24 and friction 25 from the other end are reflected in the high impedance section 36 rather than the high impedance section 36, and pressure waves penetrating the microphone capsule 21 are eliminated or reduced. Therefore, noise components detected by the transducer are reduced. The cable 22 according to this embodiment does not necessarily need to include the buffer material 26 and the second covering material 27.

[0035] One end of cable 22 may be covered with a reinforcing material mainly for the purpose of preventing microphone capsule 21 from falling off or mitigating bending fatigue. The mechanical impedance of cable 22 at the portion covered with the reinforcing material is different from the mechanical impedance at other portions of cable 22. High impedance section 36 according to this embodiment is provided separately from the reinforcing material, and its main purpose is to suppress the propagation of pressure waves caused by vibration or friction generated in other portions of cable 22 to transducer 21t.

[0036] Next, a specific example of the high impedance section 36 according to the present embodiment will be described. Fig. 4 is a plan view showing an example of the high impedance section according to the present embodiment. Fig. 5 is a side view showing an example of the high impedance section 36. In Figs. 4 and 5, the left-right direction indicates the longitudinal direction of the cable 22, with the microphone amplifier 28 connected to the left end and the microphone capsule 21 connected to the right end. High impedance section 36 is formed by wrapping (looping) base line 23 around rotation axis A. The direction of the wrapping rotation axis A is a direction intersecting the longitudinal direction of base line 23 (for example, a direction perpendicular to the longitudinal direction). The radius of curvature in the section in which base line 23 wraps around (hereinafter sometimes referred to as the "wraparound section") is typically about 2 to 5 times the diameter of base line 23.

[0037] A cushioning material 37 is fitted onto the other end of the circulating section, and is in contact with one end of the circulating section via the cushioning material 37. The shape of the circulating section is stabilized by pressing one end and the other end of the circulating section together via the cushioning material 37. At this time, since the one end and the other end of the circulating section are not in direct contact with each other, a short circuit of the pressure wave from one end of the circulating section to the other end is avoided. Note that the cushioning material 37 may be made of the same material as the cushioning material 26 (FIGS. 1 and 2). Therefore, the pressure wave traveling straight from the portion close to the other end of the cable 22 is reflected and diffracted in the circulating section, and the pressure wave arriving at the microphone capsule 21 is suppressed.

[0038] Next, another example of the high impedance section 36 according to the present embodiment will be described. Fig. 6 is a configuration diagram showing another example of the high impedance section 36 according to the present embodiment. The high impedance section 36 is formed by including a pair of connectors 38 (38-1, 38-2). The connectors 38-1, 38-2 have shapes that fit together, and have a structure that allows them to maintain a mutually coupled state even when a certain external force is applied.

[0039] The base line 23 is divided into two sections. One end of one of the two sections is connected to the connector 38-1, and the other end is connected to the microphone amplifier 28. One end of the other section is connected to the microphone capsule 21, and the other end is connected to the connector 38-2. When the connectors 38-1 and 38-2 are connected, the one section and the other section of the base line 23 are electrically connected via the connectors 38-1 and 38-2, respectively. On the other hand, even in the connected state, the mechanical impedance of the connectors 38-1 and 38-2 is higher than the mechanical impedance of each section of the base line 23. Therefore, the pressure waves arriving from one section of the base line 23 are reflected and diffracted by the connectors 38-1 and 38-2, so that the pressure waves arriving at the microphone capsule 21 are suppressed.

[0040] The mechanical impedance of connector 38-1 may be higher than the mechanical impedance of connector 38-2. This makes it possible to suppress transmission of pressure waves from one section of base line 23 through connector 38-1, and also suppress transmission of pressure waves to the other section of base line 23 due to the difference in mechanical impedance with connector 38-2.

[0041] In addition, the technical features of one or both of the first and second embodiments may be combined in any manner as long as no contradiction occurs, some may be omitted, some may be replaced with other technical features, or other technical features may be added. The microphone 20 illustrated in Fig. 1 and Fig. 2 may include a high impedance section 36 illustrated in any one of Figs. 3 to 6 in the cable 22. For example, the microphone 20 illustrated in Fig. 9 is configured by including a high impedance section 36 illustrated in Fig. 3 in the cable 22 of the microphone 20 illustrated in Fig. 1. The section in which the high impedance section 36 is provided is set to be closer to the microphone capsule 21 than the section in which the buffer material 26 and the second covering material 27 are provided. This makes it possible to further suppress the arrival of pressure waves due to vibration or rubbing at the transducer 21t.

[0042] In the above description, the transducer provided in the microphone capsule 21 is a condenser microphone based on the electret condenser system, but this is not limiting. The transducer may be a microphone based on another system, such as a dynamic microphone. A dynamic microphone does not require the application of a DC voltage such as the phantom voltage from the phantom power supply.

[0043] The number of base lines 23 or core wires 23a in cable 22 is not limited to one, and may be two or more. The number may be preset depending on the number of channels of the electrical signal transmitted from microphone capsule 21 to microphone amplifier 28. Also, the core wires 23a may be used differently depending on the polarity of the electrical signal to be transmitted.

[0044] <Preliminary experiment> Next, a verification example for the above embodiment will be described. First, as a preliminary experiment, an existing microphone was attached to the clothes worn by the performer at a position that was not visible from the outside, and an audio signal was recorded. The clothes worn by the performer were a shirt and a suit. The configuration of the existing microphone corresponds to the microphone 20 illustrated in FIG. 3 with the high impedance section 36 omitted. The microphone 20 to be verified was attached to the chest surface of the shirt. The microphone 20 attached at this position is covered by the suit jacket. Therefore, since the suit swings relative to the microphone 20 due to the performer's movements, vibration due to contact with the suit and rubbing due to movement of the contact position tend to occur. There are three recording conditions. Pattern A: A state in which the performer is made to dance without vocalizing. In this state, noise components due to the performer's movements are mainly recorded. Pattern B: A state in which the performer is made to sing while standing still. In this state, audio components due to the performer's singing are mainly recorded. Pattern C: A state in which the performer is made to stand still but not vocalize. In this state, background noise and intrinsic noise are recorded.

[0045] Fig. 10 shows the frequency characteristics of the audio signal recorded in this experiment. Curves 10a-10c show the levels of the audio signals obtained with patterns AC, respectively. According to Fig. 10, the levels of patterns A and B are 30-40 dB higher than the level of pattern C at each frequency. This shows that the levels of noise components caused by vibrations and friction due to contact with clothes are almost the same as the recorded singing.

[0046] <Vibration experiment> Next, a vibration experiment was performed to investigate the effect of vibration on the microphone. FIG. 11 is a diagram showing an experimental system used in the vibration experiment. In the vibration experiment, a rod 52 was attached to a vibrator 50, and the cable 22 of the microphone 20 was brought into contact with the surface of the rod 52. In addition, the vibrator 50 was surrounded by a soundproof box 54, except for the part where the rod 52 protrudes. The soundproof box 54 suppresses leakage of the operating sound of the vibrator 50. The contact position between the cable 22 and the rod 52 was set at a position 20 cm away from the microphone capsule 21. The vibration direction was set to a direction perpendicular to the longitudinal direction of the cable 22. In this experiment, an audio signal that forms a linear response to each contact was recorded, and the average value of the obtained linear responses for five contacts was calculated.

[0047] The following microphone 20 was used as the measurement subject. a. Existing microphone 20a (comparison example) b. Microphone 20b (FIG. 1) including buffer material 26 and one second covering material 27 according to the first embodiment c. Microphone 20c (FIG. 2) including a plurality of cushioning materials 26-1 to 26-n according to the first embodiment and second covering materials 27-1 to 27-n divided for each of the cushioning materials 26-1 to 26-n d. Microphone 20d (Comparative Example) having cable 22 in which buffer material 26 and second covering material 27 are arranged side by side so as not to overlap and cover base line 23 e. Microphone 20e having connector 38 according to the second embodiment on cable 22 (base line 23) (FIGS. 3 and 6) f. Microphone 20f wound around one end of cable 22 (base line 23) according to the second embodiment (FIGS. 3-5) g. Microphone 20g (comparative example) in which the longitudinal direction of the microphone capsule 21 is connected perpendicular to the longitudinal direction of the existing cable 22 (base line 23) h. Microphone 20h (comparative example) having a cable 22 with a thinner baseline than the baseline 23 of the existing microphone 20a

[0048] 13 and 14 are diagrams showing the measurement results in this experiment. FIG. 13 shows the linear responses obtained from the microphones 20a-20d as curves 13a-13d, respectively. According to FIG. 13, the microphones 20b-20d increase the noise components due to vibration more than the existing microphone 20a. The increase in noise components due to the microphones 20b-20d is more noticeable in the frequency band below 3 kHz than in the higher bands. This suggests that the provision of the buffer material 26 and the second covering material 27 causes the cable 22 to vibrate more significantly.

[0049] FIG. 14 shows the linear responses obtained from the microphones 20a and 20e-20h in the curves 14a and 14e-14h, respectively. According to FIG. 14, the microphones 20e-20g reduce noise components caused by vibration more than the existing microphone 20a. The reduction in noise components by the microphones 20e and 20f is remarkable in a frequency band higher than 500 Hz. In the microphone 20g, a significant reduction in noise components is observed in a frequency band from 1 kHz to 5 kHz. However, the reduction effect of the noise components by the microphone 20g is not as remarkable as that of the microphones 20e and 20f. In addition, in the microphone 20h, a significant reduction in noise components was not observed. These experimental results show that the mechanism for blocking vibration from the cable 22 to the microphone capsule 21 as in the second embodiment is effective in reducing noise components caused by vibration.

[0050] <Rubbing experiment> Next, a rubbing experiment was conducted to investigate the effect of rubbing on the microphone 20. FIG. 12 shows the experimental system used in the rubbing experiment. In the rubbing experiment, a piece of fabric was attached to the side of a turntable 56, and was brought into contact with the side of the cable 22 of the microphone 20. At this time, both ends of the cable 22 were pulled straight by fixing one end and tying a weight to the other end. Thus, by rotating the turntable 56, rubbing was applied at the contact position between the cable 22 and the side of the turntable 56. A record player for playing analog records, designed to minimize abnormal noise and vibration due to rotation, was used as the turntable 56.

[0051] In this experiment, the turntable 56 was rotated at 100 / 3 revolutions per minute, and audio signals were recorded for 20 seconds for each microphone 20, and the level of the recorded audio signal for each octave band (octave band level) was obtained. However, for the microphone 20c, audio signals were recorded when the contact position with the turntable 56 was one end of the second covering material 27-2 (contact position 1) and when the contact position was the center of the second covering material 27-2 (contact position 2). The end face of the second covering material 27-2 was not chamfered. Therefore, in the microphone 20c in which multiple second covering materials 27-i are distributed on the cable 22, the effect of rubbing differs depending on the contact position of the second covering material 27-i.

[0052] 15 and 16 are diagrams showing the measurement results in this experiment. In FIG. 15, the octave band levels of the audio signals obtained from the microphones 20a-20d are shown by broken lines 15a-15d, respectively. However, for the microphone 20c, the level obtained at the contact position 1 is shown by broken line 15c1, and the level obtained at the contact position 2 is shown by broken line 15c2. According to FIG. 15, the microphone 20b reduces noise components by 10-20 dB over the entire frequency band compared to the existing microphone 20a. The microphone 20d reduces noise components significantly more than the existing microphone 20a, although not as much as the microphone 20b. However, the effect of reducing noise components in the microphone 20c varies greatly depending on the contact position. At the contact position 2, the noise components are reduced over the entire frequency band compared to the existing microphone 20a.

[0053] The reduction in noise components of microphone 20c compared to microphone 20a is small in frequency bands below 3 kHz or equal to or higher than 5 kHz, but is significant in frequency bands between 3 kHz and less than 5 kHz. At contact position 1, noise components increase more than that of existing microphone 20a in frequency bands below 2 kHz, and noise components decrease in frequency bands of 3 kHz and higher. This is thought to be due to friction noise generated by friction between the end points of second covering material 27-2 and the side surface of turntable 56, even if the surface of second covering material 27-2 is smooth.

[0054] FIG. 16 shows the octave band levels of the audio signals obtained from the microphones 20a, 20e-20h, as broken lines 16a, 16e-16h, respectively. According to FIG. 16, the microphones 20e-20g reduce noise components due to friction more than the existing microphone 20a. The reduction in noise components by the microphones 20e, 20f is remarkable in a frequency band higher than 500 Hz. The microphone 20g reduces noise components in almost the entire band. However, the microphone 20h does not reduce noise components, and rather increases noise components in a frequency band higher than 500 Hz. These experimental results show that the noise components due to friction are suppressed by smoothing the surface as in the first embodiment. However, when the contact position is an end point of the second covering material 27, the noise components increase. Even in that case, the noise components are expected to be reduced by smoothing the end points of the second covering material 27 by chamfering. It is also shown that the mechanism for blocking vibration from cable 22 to microphone capsule 21 as in the second embodiment is effective in reducing noise components due to friction.

[0055] As described above, the microphone 20 according to the embodiment of the present application includes an electroacoustic converter (e.g., the transducer 21t) that converts mechanical vibrations into an electric signal, and a cable 22 that connects one end of the electroacoustic converter. The cable 22 has a portion (e.g., a high impedance portion 36) in a section within a predetermined range from the one end, the portion having a higher mechanical impedance than other sections. With this configuration, pressure waves caused by vibration or friction in other sections of the cable 22 are reflected at the boundary with the section with higher mechanical impedance, and transmission to the electroacoustic transducer is suppressed. Since noise components caused by vibration or friction are reduced in the electrical signal recorded by the electroacoustic transducer, it becomes possible to pick up clear sound with vibration or the effects of vibration suppressed.

[0056] The cable 22 may be wound around an axis in a direction intersecting with the longitudinal direction in a section within a predetermined range from one end. According to this configuration, the winding of the cable 22 prevents pressure waves caused by vibration or friction occurring in other sections from traveling in a straight line, thereby suppressing the propagation of noise components caused by vibration or friction to the electro-acoustic transducer.

[0057] A portion of the cable 22 may be connected to another portion of the cable 22 via connectors 38-1, 38-2 having a higher mechanical impedance than the cable 22 in a section within a predetermined range from one end. According to this configuration, the connectors 38-1 and 38-2 block pressure waves caused by vibration or friction occurring in other sections, thereby suppressing the propagation of noise components caused by vibration or friction to the electro-acoustic transducer.

[0058] A microphone 20 according to an embodiment of the present application includes an electroacoustic converter (e.g., transducer 21t) that converts mechanical vibrations into an electric signal, and a cable 22 that connects one end of the electroacoustic converter. The cable 22 includes a base line 23 that transmits an electric signal and is covered with a first covering material 23c made of an insulator, and a buffer material 26 that is fitted over the first covering material 23c at least in a section within a predetermined range from one end of the cable 22 and has more elasticity than the first covering material 23c. The microphone 20 includes a second covering material 27 that covers at least the buffer material 26 and has a smoother surface than the first covering material 23c, and is distributed in the longitudinal direction of the cable 22. This configuration reduces friction caused by contact with the second covering material 27 that covers the cable 22, thereby suppressing pressure waves caused by vibration or friction. In addition, pressure changes are mitigated by the buffer material 26, thereby suppressing the propagation of pressure waves caused by vibration or friction to the electroacoustic transducer. Noise components caused by vibration or friction are reduced in the electrical signal recorded by the electroacoustic transducer, making it possible to pick up clear audio with the effects of vibration or friction suppressed.

[0059] The cable 22 may further have a buffer material 26-2 in a second section within a predetermined range from the other end, and the second covering material 27 may cover the side surface of the cable 22 continuously. According to this configuration, the second covering material 27 is stably supported by the multiple cushioning materials 26-1, 26-2 at different positions, and friction caused by contact between the cable 22 and the second covering material 27 is reduced or eliminated. Therefore, pressure waves caused by vibration or friction are more reliably suppressed.

[0060] Cable 22 may include a plurality of buffer materials 26-1 to 26-n distributed in the longitudinal direction of cable 22, and second covering materials 27-1 to 27-n may be divided for each of buffer materials 26-1 to 26-n and cover each of buffer materials 26-1 to 26-n. According to this configuration, second covering materials 27-1 to 27-n that cover the multiple buffer materials 26-1 to 26-n, respectively, are distributed in the cable 22. Pressure waves generated in some second covering materials 27-i do not propagate directly to other second covering materials 27-j (j is an integer between 1 and n and different from i) or to buffer materials 26-j. Therefore, the propagation of pressure waves due to vibration or friction to the electroacoustic transducer is more reliably suppressed.

[0061] In the microphone 20, in a third section that is closer to the electro-acoustic transducer than the section within a predetermined range from one end, the base line 23 may have a portion (e.g., a high impedance portion 36) having a higher mechanical impedance than other sections. According to this configuration, pressure waves caused by vibration or friction occurring in other sections of the base line 23 are reflected at the boundary with the third section, and transmission to the electroacoustic transducer is suppressed, so that noise components caused by vibration or friction can be further reduced in the electrical signal recorded by the electroacoustic transducer.

[0062] One embodiment of the present invention has been described in detail above with reference to the drawings, but the features of the first embodiment and the features of the second embodiment can be combined as described above. Since the former is effective against rubbing and the latter is effective against both rubbing and vibration, it is possible to select either embodiment according to the purpose. Furthermore, the specific configuration is not limited to the above, and various design changes and the like are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0063] 20... microphone, 21... microphone capsule, 22... cable, 23... baseline, 23c... first covering material, 26 (26-1 to 26-n)... buffer material, 27 (27-1 to 27-n)... second covering material, 28... microphone amplifier, 36... high impedance section, 37... buffer material, 38 (38-1, 38-2)... connector

Claims

1. an electroacoustic transducer that converts mechanical vibrations into an electrical signal; a cable connecting one end of the electroacoustic transducer; The cable includes: The section within a predetermined range from the one end has a portion having a higher mechanical impedance than other sections. Microphone.

2. The cable includes: In the above section, the wire is wound around an axis in a direction perpendicular to the longitudinal direction.

2. The microphone of claim 1.

3. The portion of the cable includes: In the section, the cable is connected to another part of the cable via a connector having a higher mechanical impedance than the cable.

2. The microphone of claim 1.

4. an electroacoustic transducer that converts mechanical vibrations into an electrical signal; a cable connecting one end of the electroacoustic transducer; The cable includes: a base line that transmits the electrical signal and is covered with a first covering material made of an insulator; a cushioning material that is fitted onto the first covering material at least in a section within a predetermined range from the one end and has greater elasticity than the first covering material; A second covering material that covers at least the buffer material and has a smoother surface than the first covering material is provided so as to be distributed in the longitudinal direction of the cable. Microphone.

5. The cable includes: The cushioning material is further provided in a second section within a predetermined range from the other end, The second covering material continuously covers the side surface of the cable.

5. The microphone according to claim 4.

6. The cable includes: A plurality of the buffer materials are provided so as to be distributed in the longitudinal direction of the cable, The second covering material is divided into sections for each of the buffer materials and covers each of the buffer materials.

5. The microphone according to claim 4.

7. In a third section closer to the electro-acoustic transducer than the first section, The baseline is Has a section with a higher mechanical impedance than other sections 5. The microphone according to claim 4.

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