Electroacoustic transducer

Abstract

An object of the technology of the present disclosure is to measure a capacitance in which a fluctuation according to a change in a mounted state is suppressed.SOLUTION: An electroacoustic transducer includes a hollow housing attached to an ear of a user, a tubular external auditory canal insertion unit that is a part of the housing and is provided in a portion of the housing on an external auditory canal side, a signal output driver that is provided inside the external auditory canal insertion unit and has a tubular metal casing, and a measurement unit that measures a capacitance using the metal casing as an electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology of the present disclosure relates to an electro-acoustic transducer. [Background technology]

[0002] Earphones that have the added function of a capacitance sensor have been known.

[0003] For example, it is known to have a cover formed of an electrically conductive material that forms an electrode, receive a signal from the electrically conductive material, and measure capacitance using the electrically conductive material (Patent Document 1).

[0004] It is also known that a metal shell of a speaker is connected to a main board by a metal clip to form a touch electrode, which is then connected to a capacitance detection interface of the main board (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US2011 / 0007908A1 [Patent Document 2] CN102802099B Summary of the Invention [Problem to be solved by the invention]

[0006] There is a problem in that if the wearing state of the earphones changes due to vibration or other reasons, the capacitance fluctuates, resulting in erroneous sensing.

[0007] In consideration of the above, the technique of the present disclosure aims to provide an electroacoustic transducer that can measure capacitance with reduced fluctuations caused by changes in the wearing state. [Means for solving the problem]

[0008] One aspect of the present disclosure is an electro-acoustic transducer that includes a hollow housing that is worn on a user's ear, a cylindrical ear canal insertion portion that is a part of the housing and is provided on the ear canal side of the housing, a driver for signal output that has a cylindrical metal casing that is provided inside the ear canal insertion portion, and a measuring portion that measures capacitance using the metal casing as an electrode. [Effects of the Invention]

[0009] As described above, the electroacoustic transducer according to the technique of the present disclosure can measure capacitance with reduced fluctuations caused by changes in the wearing state. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an overall configuration of an electro-acoustic transducer according to an embodiment of the technique of the present disclosure. [Figure 2] FIG. 10 is an exploded perspective view of a driver portion according to an embodiment of the disclosed technique. [Figure 3] FIG. 10 is an exploded perspective view of a driver portion according to an embodiment of the disclosed technique. [Figure 4] FIG. 2A is a top view of the driver, and FIG. 2B is a side view of the driver. [Figure 5] FIG. 10 is a cross-sectional view illustrating a driver portion according to an embodiment of the disclosed technique. [Figure 6A] FIG. 10 is a diagram showing a mounting method for measuring capacitance using a metal housing as an electrode. [Figure 6B] FIG. 10 is a diagram showing a mounting method for measuring capacitance using a metal housing as an electrode. [Figure 6C] FIG. 10 is a diagram showing a mounting method for measuring capacitance using a metal housing as an electrode. [Figure 6D] FIG. 10 is a diagram showing a mounting method for measuring capacitance using a metal housing as an electrode. [Figure 7] 10 is a graph showing data recorded on the fluctuation of capacitance in a comparative example. [Figure 8]10 is a graph showing data recording fluctuations in capacitance in a method described in an embodiment of the technique of the present disclosure. [Figure 9] 1 is a cross-sectional view showing the overall configuration of an electro-acoustic transducer according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the technology of the present disclosure will be described in detail with reference to the drawings.

[0012] <Outline of embodiments of the technology of the present disclosure> When adding capacitance sensing functionality to earphones, the layout of the capacitance sensor pad is a major constraint for earphones, which require compact size.

[0013] Furthermore, in devices like conventional earphones, where capacitance sensor pads are laid out on the surface of the auricle or outside the ear canal (near the tragus), when the earphones vibrate or the wearing state changes due to body movement or user operation, even a small change can cause large fluctuations in capacitance, resulting in incorrect detection of whether the earphones are being worn or removed.

[0014] Furthermore, when adding a sensing function to earphones, there are many restrictions, particularly with regard to attachment / detachment and pulse sensing, and it is necessary to select an appropriate earphone according to the intended use or purpose.

[0015] When sensing whether the device is being worn or removed, the IR (infra-red) method requires that the transparent window and sensor be placed in a location that is less susceptible to external light and can properly capture reflections. The capacitive method requires that the capacitive sensor pad be placed in a location that comes into close contact with the skin when the device is worn. In both cases, the size of the window and pad is a few millimeters. 2 This required a space of about 100 mm, which was a constraint that made design difficult for earphones, which are becoming increasingly miniaturized.

[0016] When it comes to pulse sensing, the photoplethysmographic method is subject to the same "restrictions on placement" as the detachable IR method, and the passive acoustic sensing method has the restriction that "sensing is not possible unless the ear canal is securely sealed."

[0017] Therefore, in an embodiment of the technique of the present disclosure, in an ear canal insertion type electroacoustic transducer, in order to use the metal housing of the driver as a capacitance sensor pad, a part of the metal housing is shaped like a terminal, thereby imparting the function of a capacitance sensor that can be inserted into the ear canal, thereby enabling the capacitance fluctuations in the ear canal to be acquired.

[0018] <Configuration of electroacoustic transducer according to embodiment of technique of the present disclosure> 1, an electroacoustic transducer 100 according to an embodiment of the technique of the present disclosure has a hollow housing 40 that houses various functional components and is worn on a user's ear. The electroacoustic transducer 100 also has a cylindrical ear canal insertion portion 42 that is part of the housing 40 and has a hollow portion 42A and is provided on the ear canal side of the housing 40 when worn on the user's ear.

[0019] The electroacoustic transducer 100 also has a driver 1 for signal output that is provided inside the ear canal insertion portion 42. It is sufficient that at least a portion of the driver 1 is provided inside the ear canal insertion portion 42, and it is preferable that half or more of the driver 1 is provided inside the ear canal insertion portion 42.

[0020] The electroacoustic transducer 100 also includes a playback unit 50 that outputs a signal from the driver 1, a measurement unit 48 that measures capacitance using the metal casing of the driver 1 as an electrode, a calculation unit 52 that calculates bioinformation based on the capacitance measured by the measurement unit 48, and an output unit 53 that outputs the calculation results by the calculation unit 52.

[0021] The measurement unit 48, the reproduction unit 50, the calculation unit 52, and the output unit 53 are mounted on a printed wiring board (not shown) disposed inside the housing 40.

[0022] Next, a specific configuration of the driver 1 will be described.

[0023] Fig. 2 is an exploded perspective view of the driver 1 according to the embodiment of the disclosed technique as seen from one side in the direction of the central axis O, Fig. 3 is an exploded perspective view of the driver 1 according to the embodiment of the disclosed technique as seen from the other side in the direction of the central axis O, Fig. 4 (a) is a top view of the driver 1, (b) is a side view of the driver 1, and Fig. 5 is a cross-sectional view along line IV-IV. The configuration of the driver 1 will be described below with reference to these figures.

[0024] The driver 1 mainly comprises a cylindrical metal housing 2 that forms the outer shell, inside which are provided a diaphragm assembly 3, a magnetic circuit 4 that drives the diaphragm assembly 3, a plate member 5 that is connected to the magnetic circuit 4, a screen 6 that is provided within the plate member 5, and a terminal 7 that is provided on the outer surface of the plate member 5. The metal housing 2 is made of a conductive material that forms an electrode.

[0025] Specifically, the cylindrical metal casing 2 has an outer shape in which the diameter of one end in the direction of the central axis O gradually decreases toward the tip, and a sound emitting opening 2a is formed in one end face, while the other end face of the metal casing 2 is left open.

[0026] In the diaphragm assembly 3, the periphery of a diaphragm 10 made of pulp, film, or the like is supported by an annular frame 11. Diaphragm 10 has a flat, circular central surface 10a in the center, and an annular edge portion 10b that rises to one side in the direction of central axis O is formed on the periphery of central surface 10a. A voice coil 12 (coil) wound in a cylindrical shape coaxial with central axis O is connected to the back surface (the surface on the other side in the direction of central axis O) of the peripheral portion of central surface 10a of diaphragm 10, and vibrations of voice coil 12 are transmitted to diaphragm 10. Two lead wires 12a of a wire that forms a coil extend outward from voice coil 12.

[0027] The magnetic circuit 4 is made up of a magnet 20, a pole piece 21 connected to one polarity of the magnet 20, and a yoke 22 connected to the other polarity. The pole piece 21 and the yoke 22 are made of a magnetic material.

[0028] The magnet 20 has a cylindrical shape with a diameter larger than that of the voice coil 12, and is disposed coaxially with the voice coil 12. The magnet 20 has polarities in the direction of the central axis O, with one polarity (e.g., S pole) on one side of the direction of the central axis O and the other polarity (e.g., N pole) on the other side of the direction of the central axis O.

[0029] The pole piece 21 has an annular shape and is disposed on the outer periphery of the voice coil 12. A stepped portion 21a is formed on the peripheral edge of one surface of the pole piece 21 in the direction of the central axis O, with which the frame 11 of the diaphragm assembly 3 engages. The pole piece 21 also has cutouts 21b formed therein for passing the two lead wires 12a of the voice coil 12 therethrough.

[0030] The yoke 22 is composed of a center pole 30 whose tip is positioned on the inner periphery of the voice coil 12 and extends along the central axis O, and a disk-shaped flat plate portion 31 that extends radially outward from the base of the center pole 30 and is connected to the magnet 20.

[0031] The center pole 30 is formed of a cylindrical portion 30a on the tip side and a conical portion 30b on the base side. The diameter of the conical portion 30b increases from the tip, which is the boundary with the cylindrical portion 30a, toward the base side (the other side in the direction of the central axis O) along the central axis O.

[0032] Specifically, the diameter of the conical portion 30b increases from the tip side to the base side, and is larger than the diameter of the voice coil 12, but is inclined within a range that prevents interference between the voice coil 12 and the center pole 30 even when the voice coil 12 vibrates due to current flow. More specifically, as shown in FIG. 5 , the tip of the conical portion 30b is located at approximately the same position as the other end of the voice coil 12 in the direction of the central axis O. Note that the tip position of the conical portion 30b is not limited to this position, and it may be located at a position radially opposite the inner peripheral surface of the voice coil 12. The diameter of the base of the conical portion 30b is formed on the outer periphery side of the outer peripheral surface of the voice coil 12, and particularly in this embodiment, it is formed close to the inner diameter of the magnet 20.

[0033] The flat plate portion 31 is disk-shaped with a diameter slightly larger than the outer diameter of the magnet 20. Three air vents 31a are formed in the flat plate portion 31 at three locations spanning the base of the center pole 30. The air vents 31a connect space A on one side of the flat plate portion 31 connected to the magnet 20 (one side in the direction of the central axis O) with space B on the other side (the other side in the direction of the central axis O) opposite the one side. Each air vent 31a is a circular hole, and the base of the center pole 30 is partially cut out to fit the shape of each air vent 31a. The opening on one side of each air vent 31a is partially blocked by the magnet 20.

[0034] In addition, a circular arc-shaped notch 31b is formed in a part of the periphery of the flat plate portion 31, through which two lead wires 12a of the voice coil 12 are passed.

[0035] Plate member 5 is disk-shaped with a stepped periphery and is attached to the other side of flat plate portion 31 of yoke 22. As a result, plate member 5 defines space B on the other side of flat plate portion 31 of yoke 22, which communicates with each vent hole 31a. A vent hole 5a that communicates the internal space with the outside is formed at the center of plate member 5. In addition, arc-shaped notches 5b are formed in part of the periphery of plate member 5, through which two lead wires 12a of voice coil 12 pass.

[0036] The screen 6 is a circular, membrane-shaped, breathable acoustic resistance material, and is provided so as to cover the ventilation holes 5a within the space formed by the plate member 5. An annular double-sided tape 6a is attached to the other side of the screen 6, and the screen 6 is attached to the plate member 5 via the double-sided tape 6a.

[0037] The terminal 7 is a circular plate material with a central hole 7a formed therein, and one surface of the terminal 7 in the direction of the central axis O is bonded to the plate member 5, and an electrode 7b is formed on the surface of the terminal 7 in the direction of the central axis O. In addition, an arc-shaped notch 7c is formed in part of the periphery of the terminal 7 to allow two lead wires 12a of the voice coil 12 to pass through.

[0038] The notch 21b of the pole piece 21, the notch 31b of the flat portion 31 of the yoke 22, the notch 5b of the plate member 5, and the notch 7c of the terminal 7 are all positioned on approximately the same line parallel to the central axis O, and the two lead wires 12a of the voice coil 12 pass through the notches 21b, 31b, 5b, and 7c to connect to the electrode 7b of the terminal 7. Although not shown, a UV adhesive is applied along the circumferential direction to the annular gap between the metal housing 2 and the plate member 5, sealing the gap between the metal housing 2 and the plate member 5. The two lead wires 12a passing through the notch 5b of the plate member 5 are also bonded with the UV adhesive. Therefore, in the driver 1 configured in this manner, the space on the back side of the diaphragm 10 is closed up to the air vent 5a of the plate member 5 via the screen 6.

[0039] When an electrical signal is sent to the electrode 7b of the terminal 7 of the driver 1 configured as described above, current is passed through the voice coil 12 via the lead wire 12a, and the voice coil 12 vibrates in response to the electrical signal, causing the diaphragm 10 to vibrate, and sound is emitted from the sound-emitting opening 2a.

[0040] Next, a mounting method for measuring capacitance using the metal casing 2 as an electrode will be described.

[0041] 6A, in the first mounting method, a lug 60 that can be soldered to the metal casing 2 is formed. In this case, the measuring unit 48 measures the capacitance by the self-capacitance method, using the metal casing 2 as an electrode.

[0042] In the second mounting method, as shown in FIG. 6B, in addition to the first mounting method,

[0043] An attachment board 62 has an insertion hole for inserting the driver 1, and electrodes 64 are printed around the insertion hole. In this case, the measurement unit 48 measures the capacitance using a mutual capacitance method in which the metal housing 2 is used as RX and the electrodes 64 printed on the attachment board 62 are used as TX.

[0044] 6C, in addition to the first mounting method, the third mounting method involves printing electrodes 66 on a flexible substrate 65, and wrapping the flexible substrate 65 around a portion of the circumferential surface of the metal casing 2. As a result, the electrodes 66 are formed over a portion of the circumferential surface of the metal casing 2. In this case, the measuring unit 48 measures the capacitance by a mutual capacitance method using the metal casing 2 as RX and the electrodes 66 printed on the flexible substrate 65 as TX.

[0045] In the fourth mounting method, as shown in Fig. 6D, the metal housing 2 mounted by the first mounting method is divided in the circumferential direction. A lug 60 that can be soldered is formed on each of the divided metal housings 68. In this case, the measuring unit 48 measures the capacitance by a mutual capacitance method using the multiple metal housings 68 as TX and RX.

[0046] The calculation unit 52 calculates biological information based on the capacitance measurement results by the measurement unit 48. For example, blood flow rate and sweat rate are calculated as biological information.

[0047] The output unit 53 outputs the calculation results or measurement results of the biological information. For example, the calculation results or measurement results of the biological information are transmitted to another terminal via wireless communication. Alternatively, the calculation results or measurement results of the biological information are output as audio from the driver 1. Alternatively, the calculation results or measurement results of the biological information are transmitted to an external output device via wireless communication, and the calculation results or measurement results of the biological information are output as audio or displayed from the external output device.

[0048] <Operation of the electroacoustic transducer according to the embodiment of the technique of the present disclosure> When the housing 40 of the electroacoustic transducer 100 is worn on the ear of a user and an instruction to measure biological information is received via wireless communication from the user's terminal (not shown), the measurement unit 48 measures the capacitance using the metal casing 2 as an electrode. Then, the calculation unit 52 calculates the biological information based on the measurement result of the capacitance by the measurement unit 48, and the output unit 53 outputs the calculation result of the biological information.

[0049] <Example> First, as a comparative example, an electroacoustic transducer was constructed so that a capacitance sensor pad formed from a flexible substrate was located outside the ear canal insertion portion. Data recording the capacitance fluctuations resulting from the attachment, vibration, and removal of the electroacoustic transducer for this comparative example are shown in Figure 7. In this data, the pressure and vibration during attachment appear as relatively large fluctuations in capacitance.

[0050] Specifically, in the comparative example, when the electroacoustic transducer moves, the ear canal insertion part moves as a fulcrum, and the distance between the capacitance sensor pad and the auricle changes, resulting in large fluctuations in the output value from the capacitance sensor.

[0051] Next, Fig. 8 shows the change in capacitance due to the attachment of the electroacoustic transducer 100, the vibration of the electroacoustic transducer 100, and the removal of the electroacoustic transducer 100, in the method described in the embodiment of the technique of the present disclosure. The operations for acquiring data are generally the same as those in Fig. 7.

[0052] A comparison between FIG. 7 and FIG. 8 also shows that the method described in the embodiment of the technique of the present disclosure is less affected by fluctuations in capacitance due to pressure or vibration when attached.

[0053] Specifically, even if the electroacoustic transducer 100 moves, the fulcrum and the metal housing are the same, so no large fluctuation in distance occurs. Also, even if the position of the metal housing displaces within the ear canal, if one side of the metal housing moves closer to the human body, the other side of the metal housing displaces away, so ultimately the displacements are canceled out and no large fluctuation occurs.

[0054] Table 1 also shows the amount of change in the proximity sensor output value when worn for the method of the comparative example and the method described in the embodiment of the technique of the present disclosure.

[0055] [Table 1]

[0056] From Table 1, it can be seen that the method described in the embodiment of the technique of the present disclosure measures capacitance closer to the human body and has smaller individual differences.

[0057] As described above, according to the electroacoustic transducer according to the embodiment of the technique of the present disclosure, a driver for signal output having a cylindrical metal housing is provided inside the cylindrical ear canal insertion portion, and capacitance is measured using the metal housing as an electrode. This makes it possible to measure capacitance with reduced fluctuations caused by changes in the wearing state.

[0058] Furthermore, the metal housing that functions as a capacitance sensor pad can be positioned in a location that allows for reliable sensing, and the space occupied by the capacitance sensor pad can be eliminated. This makes it possible to minimize fluctuations in capacitance even when the wearing state changes due to vibration, etc. Furthermore, by using an ear tip as shown in the examples below, the ear tip fits tightly against the inner surface of the ear canal, preventing the electro-acoustic transducer from changing its position within the ear canal, allowing the metal housing that functions as a capacitance sensor pad to be stably positioned in a location that allows for reliable sensing.

[0059] Furthermore, in electroacoustic transducers whose primary purpose is to hear sound, the fit of the cylindrical ear canal insertion portion inserted into the ear canal is a priority consideration in achieving the primary purpose. In this embodiment, by providing the metal housing of the driver placed inside the cylindrical ear canal insertion portion with the function of a capacitance sensor pad, it is possible to position the metal housing functioning as a sensor pad in a location that is expected to be inserted reliably into the ear canal. Furthermore, there is no need to allocate a dedicated space for the capacitance sensor pad. Furthermore, because no optical attachment / detachment sensor / pulse wave sensor is used, there is no need to consider the placement of these optical windows or sensor ICs.

[0060] In addition, since the metal housing of the driver is inserted into the ear canal and the entire outer circumference is covered by the human body, it is possible to minimize fluctuations in capacitance value caused by changes in the wearing condition (changes in position relative to the human body).

[0061] As a method of sensing pulse waves, there is an acoustic sensing method that uses intra-aural sounds, which is different from the method that uses light. In this acoustic sensing method, it is necessary to sense extremely low-frequency pressure fluctuations, so it is necessary to seal the ear canal. In the method of this embodiment, the pulse wave is sensed based on changes in electrostatic capacitance, so the seal required in the acoustic sensing method is not necessary, and it is also possible to sense pulse waves using a semi-canal-type electro-acoustic transducer that is well-ventilated.

[0062] Furthermore, because fluctuations caused by changes in the wearing state are kept small, it is possible to acquire biometric information with high accuracy. This makes it possible to acquire minute fluctuations in capacitance due to changes in blood flow (see Non-Patent Document 1), and to estimate heart rate, stress level, brain activity, etc.

[0063] [Non-Patent Document 1]: "Capacitive Sensing for Pulse Rate Monitoring." Conference: BIODEVICES 2010 - Proceedings of the Third International Conference on Biomedical Electronics and Devices, Valencia, Spain, January 20-23, 2010

[0064] <Example> An example of the electroacoustic transducer according to the embodiment of the technique of the present disclosure will be described below. As shown in Fig. 9, the housing 40 of the electroacoustic transducer of this example is formed by fitting a main housing 101a and a front housing 101b together.

[0065] Main housing 101a is a hollow member having an overall cylindrical shape, and its rear opening is closed by cover 102. A printed wiring board 103 is disposed inside main housing 101a, facing the opening. Printed wiring board 103 is a board on which electronic components that function as measurement unit 48, reproduction unit 50, calculation unit 52, and output unit 53 are mounted.

[0066] A battery 106 is disposed in front of the printed wiring board 103 via a battery cushion 107 and a battery cap 108 .

[0067] 9, housing rubber 109 is provided on the outer periphery of main housing 101a. Housing rubber 109 is a cylindrical elastic member fitted onto the outer periphery of main housing 101a, which reduces contact with the ear and prevents water from entering housing 40.

[0068] 9, front housing 101b is disposed so as to close the front opening of cylindrical main housing 101a. Front housing 101b has an overall oblique truncated cone shape, with part of the periphery slightly raised toward the eardrum.

[0069] An ear canal insertion portion 42 is provided in front of the front housing 101b, protruding from the apex of the oblique truncated cone toward the eardrum. The ear canal insertion portion 42 is cylindrical and provided in a portion of the front housing 101b. It is open at both the front and rear, allowing communication between the inside and outside of the front housing 101b. A driver 1 having a cylindrical case is installed inside the ear canal insertion portion 42. Therefore, a positioning portion 111 for the driver 1 is provided near the front opening of the ear canal insertion portion 42, and the front end of the driver 1 engages with this positioning portion 111, thereby fixing the driver 1 to the inner surface of the ear canal insertion portion 42. The rear end of the driver 1 is positioned near the front end of the front housing 101b. The driver 1 includes a magnetic circuit for generating an output signal, a diaphragm, and the like, within a cylindrical case, and an appropriate well-known structure is used.

[0070] As shown in FIG. 9 , an earpiece 113 is fixed to the outer periphery of the ear canal insertion portion 42. The earpiece 113 is also called an eartip, earpad, or earcap, and is made of an elastic material such as silicone rubber. The earpiece 113 has a cylindrical portion 113b that fits around the outer periphery of the ear canal insertion portion 42, and a hemispherical portion 113a at the tip of the cylindrical portion 113b that fits around the ear canal wall. An earpiece attachment groove 412 is provided on the outer periphery of the ear canal insertion portion 42, and as shown in FIG. 9 , a fitting portion 113c is provided on the inner periphery of the cylindrical portion 113b of the earpiece 113. The fitting portion 113c engages with the earpiece attachment groove 412, thereby fixing the earpiece 113 to the ear canal insertion portion 42.

[0071] The present invention is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0072] 1 Driver 2 Metal housing 40 Housing 42 Ear canal insertion part 42A Hollow part 48 Measuring part 50 Playback Department 52 Arithmetic section 53 Output section 60 rugs 62 Mounting board 64 electrodes 65 Flexible PCB 66 electrodes 68 Metal Case 100 Electroacoustic Transducer

Claims

1. a hollow housing that is fitted over a user's ear; a cylindrical ear canal insertion portion provided in a part of the housing on the ear canal side; a driver for signal output having a cylindrical metal housing provided inside the ear canal insertion portion; a measurement unit that measures capacitance using the metal casing as an electrode; An electroacoustic transducer comprising:

2. 2. The electroacoustic transducer according to claim 1, wherein the measuring section measures the electrostatic capacitance by a self-capacitance method using the metal casing as an electrode.

3. a substrate having an insertion hole for inserting the driver, the substrate having electrodes printed around the insertion hole; 2. The electroacoustic transducer according to claim 1, wherein the measurement unit measures the electrostatic capacitance by a mutual capacitance method using the metal housing and electrodes printed on the substrate.

4. The metal housing further includes a substrate wrapped around a portion of the periphery thereof, the substrate having electrodes printed over the periphery of the portion; 2. The electroacoustic transducer according to claim 1, wherein the measurement unit measures the electrostatic capacitance by a mutual capacitance method using the metal housing and electrodes printed on the substrate.

5. the metal housing is a plurality of metal housings divided in a circumferential direction, 2. The electroacoustic transducer according to claim 1, wherein the measurement unit measures the electrostatic capacitance by a mutual capacitance method using the plurality of metal housings.

6. 2. The electroacoustic transducer according to claim 1, further comprising a calculation unit that calculates biological information based on the capacitance measured by the measurement unit.

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