Capacitive electroacoustic transducer

Abstract

According to the present invention, an earphone 1 includes: a resonance circuit 122 that outputs an adjustment signal in which a signal component included in an electric signal output by a sound source device 2 and having a predetermined resonance frequency is larger than a signal component having another frequency; a fixed pole 22 fixed to a housing; a diaphragm 25 that is provided to face the fixed pole 22 and vibrates, on the basis of the adjustment signal, according to a potential difference generated between the diaphragm 25 and the fixed pole 22; a contact part 29 that is in contact with a partial area of the diaphragm 25 and presses the area toward the fixed pole 22; and a sound emitting part 30 that emits, to the outside of the housing, a sound generated by the vibration of the diaphragm 25.

Description

[Technical field]

[0001] The present invention relates to a capacitive-type electro-acoustic transducer that converts an electrical signal into sound. [Background technology]

[0002] There is known a capacitive electroacoustic transducer that converts an electric signal into sound by the vibration of a diaphragm caused by the electric signal. Patent Document 1 discloses a magnetic earphone that generates sound by passing a current through a coil arranged in a magnetic circuit and changing the attractive force of the coil to vibrate the diaphragm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-204844 A Summary of the Invention [Problem to be solved by the invention]

[0004] Magnetic earphones can only reproduce sounds over a narrow frequency range (i.e., dynamic range). To achieve a wider dynamic range, it is necessary to combine multiple units for low, mid, and high frequencies, which means that there are more parts required than with condenser headphones (capacitive headphones), making miniaturization difficult.

[0005] On the other hand, in order to increase the sensitivity of condenser headphones, it is necessary to increase the capacitance, and therefore to reduce the distance between the diaphragm and the fixed pole. However, if the distance between the diaphragm and the fixed pole is made too small, there is a problem that the diaphragm will come into contact with the fixed pole due to vibration, causing a short circuit.

[0006] The present invention has been made in consideration of these points, and has an object to provide a capacitive electroacoustic transducer that can achieve a wide dynamic range and a compact size. [Means for solving the problem]

[0007] The capacitive electroacoustic converter of the present invention comprises a resonant circuit that outputs an adjustment signal in which a signal component of a predetermined frequency contained in an electrical signal output by a sound source device is made larger than signal components of other frequencies, a fixed pole fixed to a housing, a diaphragm disposed opposite the fixed pole and vibrating in response to a potential difference generated between the diaphragm and the fixed pole based on the adjustment signal, a contact portion that contacts a partial area of ​​the diaphragm and presses the area against the fixed pole, and a sound emitting portion that emits sound generated in association with the vibration of the diaphragm outside the housing.

[0008] The capacitive electroacoustic transducer may further have a connection portion connected to the sound source device, and the resonant circuit may have a resistor and an inductor connected in series with each other between the connection portion and the diaphragm, and a capacitive circuit provided between the fixed pole and the diaphragm.

[0009] The capacitance value of the capacitance circuit may be ten times or more the capacitance value of an electroacoustic transducer including the fixed pole, the diaphragm, the contact portion, and the sound emitting portion.

[0010] The capacitive electroacoustic transducer may further include a control unit that acquires setting information for setting a capacitance value of the capacitance circuit and controls the capacitance value based on the acquired setting information.

[0011] The sound source device may be an information terminal that executes an application program, and the control unit may acquire the setting information inputted in the information terminal that is executing the application program.

[0012] The capacitance circuit may have a capacitor connection portion that connects the capacitor between the fixed pole and the diaphragm in a state in which the capacitor connected between the fixed pole and the diaphragm is interchangeable.

[0013] The capacitor connection portion may be exposed to the outside of a housing of the capacitive electroacoustic transducer.

[0014] The capacitance generated by the fixed pole and the diaphragm may be 60 pF or more, and the inductor may have an inductance value of 2.0 H or less.

[0015] The resonant frequency of the resonant circuit may be 10 KHz.

[0016] A distance between the diaphragm and the fixed pole in a partial region of the diaphragm may be narrower than a distance between the diaphragm and the fixed pole outside the partial region.

[0017] A distance between the diaphragm and the fixed pole at a central portion of the diaphragm may be narrower than a distance between the diaphragm and the fixed pole outside the central portion of the diaphragm.

[0018] As the distance from the center of the diaphragm approaches the outer edge of the diaphragm, the distance between the diaphragm and the fixed pole decreases. Wide It's okay to be. Effect of the Invention

[0019] According to the present invention, it is possible to achieve an effect of widening the dynamic range of a capacitive electroacoustic transducer and reducing its size. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a configuration of an electroacoustic conversion system S. [Diagram 2] FIG. 2 is an enlarged view of the earphone 1. [Diagram 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line BB in FIG. [Diagram 5] 5 is a view of the earpiece 14 side taken along line CC in FIG. 4. FIG. [Figure 6] 2 is a diagram showing an electric circuit of the earphone 1. FIG. [Figure 7] 10 is a diagram showing measurement results of frequency characteristics of the sensitivity of an earphone 1 that does not have a series resonant circuit. FIG. [Figure 8] 1 is a diagram showing measurement results of frequency characteristics of the sensitivity of an earphone 1 having a series resonant circuit. [Figure 9] 1 is a diagram showing a resonant circuit 122a which is a first modified example of the resonant circuit 122. FIG. [Figure 10] 13 is a diagram showing a resonant circuit 122b which is a second modified example of the resonant circuit 122. FIG. [Figure 11] FIG. 2 is a diagram showing the internal configuration of an electroacoustic transducer 20a. [Figure 12] FIG. 12 is a cross-sectional view taken along line DD in FIG. [Figure 13] FIG. 2 is a diagram showing the internal configuration of an electroacoustic transducer 20b. [Figure 14] FIG. 2 is a diagram showing the internal configuration of an electroacoustic transducer 20c. [Figure 15] 11 is a diagram showing the shape of a displacement portion 28a. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [Outline of the electroacoustic conversion system S] 1 is a diagram showing the configuration of an electroacoustic conversion system S. The electroacoustic conversion system S has an earphone 1 and a sound source device 2. The earphone 1 is an example of a capacitive electroacoustic conversion device, which converts an electrical signal output from the sound source device 2 into sound and emits the sound to the outside.

[0022] The sound source device 2 is, for example, a smartphone, a computer, or an audio player that is an information terminal that executes an application program, and outputs an electrical signal based on sound source data including music, voice, etc. The sound source device 2 may store the sound source data in a storage medium, or may obtain the sound source data from an external device via a communication line.

[0023] Fig. 2 is an enlarged view of the earphone 1. Fig. 2(a) is a perspective view of the earphone 1, and Fig. 2(b) is a side view of the earphone 1. The earphone 1 is, for example, an electret-type capacitive electroacoustic transducer, and converts an electric signal into sound by changing the electrostatic capacitance between a fixed pole and a diaphragm. Therefore, the earphone 1 does not have a magnet for generating sound.

[0024] The earphone 1 has a connection portion 10, a cable 11, a rear housing 12, a front housing 13, and an earpiece 14. An opening 15 for emitting sound to the outside is formed at the tip of the earpiece 14.

[0025] The connection unit 10 is connected to a terminal of the sound source device 2 that outputs sound, and includes an amplifier that amplifies an electric signal output from the terminal. The sensitivity of a capacitive electroacoustic transducer is lower than that of electrodynamic or balanced armature electroacoustic transducers. Therefore, in the capacitive electroacoustic transducer, the connection unit 10 amplifies the electric signal so that a volume suitable for listening to music can be output. The amplifier may include a step-up transformer or an amplifier for amplifying the signal.

[0026] The cable 11 is a cable for transmitting an electric signal supplied from a sound source. The rear housing 12 is a portion provided between the cable 11 and the front housing 13. The rear housing 12 has an electroacoustic transducer 20 that converts the electric signal transmitted via the cable 11 into sound. The internal configuration of the electroacoustic transducer 20 will be described in detail later.

[0027] The front housing 13 is provided between the rear housing 12 and the earpiece 14, and has a structure that allows the angle with respect to the rear housing 12 to be variable. The earpiece 14 is the part of the earphone 1 that is inserted into the ear of the user, and is coupled to a sound guide tube that protrudes from the front housing 13. The earpiece 14 emits the sound generated by the electro-acoustic transducer 20 from an opening 15.

[0028] [Detailed configuration of electroacoustic transducer 20] Fig. 3 to Fig. 5 are schematic diagrams showing the internal configuration of the electroacoustic transducer 20. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2. Fig. 4 is a cross-sectional view taken along line BB in Fig. 3. Fig. 5 is a view of the earpiece 14 side taken along line CC in Fig. 4.

[0029] As shown in Figures 3 to 5, the electroacoustic transducer 20 has a housing 21, a fixed pole 22, a fixed pole cover 23, a terminal 24, a diaphragm 25, an insulating member 26, a conductive member 27, a displacement portion 28, and a contact portion 29.

[0030] The housing 21 is formed of, for example, resin, and has a space for accommodating components that generate sound based on an electrical signal supplied from a sound source. The housing 21 has a sound emitting section 30 that communicates with the space. The sound emitting section emits sound generated based on the electrical signal to the outside via the earpiece 14. The sound emitting section 30 is, for example, a cylindrical section, and extends toward the earpiece 14. The housing 21 may function as an exterior member of the rear housing 12.

[0031] The side of housing 21 that receives an electric signal is connected to connection portion 10 via cable 11, and the side of housing 21 that emits sound is connected to earpiece 14. In the examples shown in Figures 3 to 5, housing 21 has a circular cross section, but the shape of housing 21 is arbitrary, and housing 21 may have a polygonal cross section.

[0032] The fixed electrode 22 is formed of a flat conductive member (e.g., aluminum). The fixed electrode 22 generates an electric field between itself and the diaphragm 25 due to an external electric field caused by, for example, an electret. An electric signal input from a sound source is input to the fixed electrode 22 and the diaphragm 25 via the terminal 24 and the conductive member 27, respectively. The fixed electrode 22 may generate an electric field between itself and the diaphragm 25 due to a bias voltage applied via the terminal 24 instead of the electret.

[0033] The fixed pole 22 is fixed to the housing 21 via, for example, a fixed pole cover 23. The shape and size of the fixed pole 22 are arbitrary, but the fixed pole 22 is, for example, a disk shape with a diameter of 20 mm. The fixed pole 22 is formed with a plurality of sound holes 221 that allow sound generated by vibration of the diaphragm 25 to pass through.

[0034] The fixed pole cover 23 has a recess for accommodating the fixed pole 22. The fixed pole cover 23 is made of an insulating material. Since the outer edge of the fixed pole 22 is surrounded by the insulating material, the fixed pole 22 is electrically insulated from a conductive member 27 described later.

[0035] The terminal 24 is a conductive terminal for supplying an electric signal to the fixed electrode 22. The terminal 24 is a first conductive part connected to the fixed electrode 22, and is disposed on the side of the fixed electrode 22 opposite to the side of the sound emitting part 30. The terminal 24 is electrically coupled to the fixed electrode 22. An electric signal supplied from a sound source is input from the terminal 24 after being superimposed on a bias voltage or a surface potential of the electret.

[0036] The diaphragm 25 is disposed opposite the fixed electrode 22 and is a diaphragm that vibrates based on an electric signal supplied from a sound source. The diaphragm 25 is formed of a thin film having electrical conductivity. The diaphragm 25 is formed of, for example, a metal foil or a polymer film on which gold is vapor-deposited.

[0037] The diaphragm 25 vibrates in response to a potential difference caused by an electric signal supplied from the sound source device 2. Specifically, the diaphragm 25 vibrates in response to a potential difference caused between the diaphragm 25 and the fixed pole 22 based on an electric signal applied via the terminal 24 and the conductive member 27. More specifically, the diaphragm 25 vibrates in response to a potential difference caused between the diaphragm 25 and the fixed pole 22 based on an adjustment signal, which is an electric signal after the frequency characteristics of the electric signal have been adjusted by the resonant circuit 122 described later.

[0038] A portion of the diaphragm 25 (the central portion in the example shown in FIG. 4) is pressed against the fixed pole 22 by the contact portion 29, and the distance between the diaphragm 25 and the fixed pole 22 in the portion is narrower than the distance between the diaphragm 25 and the fixed pole 22 outside the portion. In the example shown in FIG. 4, the distance between the diaphragm 25 and the fixed pole 22 becomes narrower from the central portion of the diaphragm 25 to the outer edge of the diaphragm 25. Wide The diaphragm 25 comes into contact with the fixed pole 22 at a portion thereof due to the pressure applied by the contact portion 29. Since the diaphragm 25 is configured in this manner, the distance between the diaphragm 25 and the fixed pole 22 varies depending on the position on the diaphragm 25, improving the sensitivity of the electro-acoustic transducer 20 to electrical signals in a wide frequency range.

[0039] Furthermore, since the distance between at least a portion of the area of ​​the diaphragm 25 and the fixed pole 22 can be reduced, the capacitance of the electroacoustic transducer 20 is increased. By increasing the capacitance of the electroacoustic transducer 20, the inductance value of the inductor constituting the resonant circuit 122 described below can be reduced. Furthermore, such a configuration contributes to reducing the signal amplification by the connection portion 10. Conventional electrostatic electroacoustic transducers had to greatly amplify the electric signal in order to output a volume that is tolerable for listening to music. A configuration in which the distance between the fixed pole and a portion of the area of ​​the diaphragm is reduced can reduce the degree of amplification of the electric signal, allowing the step-up transformer and amplifier to be made smaller.

[0040] The insulating member 26 is provided to prevent the diaphragm 25 from being electrically connected to the fixed pole 22, and is made of, for example, resin. The entire insulating member 26 may be made of an insulating material, or at least one of the surface of the insulating member 26 that contacts the fixed pole 22 and the surface of the insulating member 26 that contacts the diaphragm 25 may have insulating properties.

[0041] The insulating member 26 has, for example, an annular shape, and is sandwiched between the peripheral portion of the diaphragm 25 and the fixed pole 22. As a result, the peripheral portion of the diaphragm 25 is fixed without contacting the fixed pole 22, and the area of ​​the diaphragm 25 that is not in contact with the insulating member 26 vibrates in response to an electric signal.

[0042] The conductive member 27 is a member for applying an electric signal to the diaphragm 25. The conductive member 27 is a second conductive part, and is connected to the diaphragm 25 on the side of the sound emitting part 30 with respect to the fixed pole 22. The conductive member 27 is formed of, for example, a conductive sheet. The conductive member 27 has an annular part 271 that contacts the peripheral part of the diaphragm 25, and an extension part 272 that extends from at least a part of the annular part 271 to the side opposite the sound emitting part 30 with respect to the fixed pole 22. The extension part 272 extends to the side of the rear housing 12 through between the housing 21 and the fixed pole cover 23 and the insulating member 26.

[0043] The displacement portion 28 and the contact portion 29 constitute a support portion that supports a partial area of ​​the diaphragm 25 toward the fixed pole 22, and apply pressure to the partial area of ​​the diaphragm 25. The displacement portion 28 is formed, for example, from a rod-shaped elastic resin, spring, or rubber, and displaces in a direction in which the diaphragm 25 is displaced in response to a change in pressure inside the housing 21. Specifically, when the diaphragm 25 is displaced in response to a change in pressure inside the housing 21 that occurs when the earpiece 14, which is a part of the housing of the earphone 1, is placed in a person's ear or when the earpiece 14 is removed from the person's ear, the displacement portion 28 is displaced by receiving a stress generated by the displacement of the diaphragm 25.

[0044] In the example shown in Fig. 5, the displacement section 28 is provided at a position crossing the sound emitting section 30. The displacement section 28 has one or more rod-shaped members crossing the sound emitting section 30. Specifically, the displacement section 28 has a plurality of rod-shaped members having one end fixed to the opening of the sound emitting section 30. In the example shown in Fig. 5, three rod-shaped members extending in different directions by 120 degrees from the opening on the diaphragm 25 side of the sound emitting section 30 are joined in the center of the sound emitting section 30, but the direction in which the rod-shaped members extend and the number of rod-shaped members are arbitrary.

[0045] The rod-shaped member of displacement section 28 may be formed by integral molding with housing 21, or a rod-shaped member different from housing 21 may be fixed to housing 21 by adhesive or the like. The rod-shaped member shown in Fig. 5 has a uniform thickness, but the rod-shaped member may have a shape that becomes thinner as it approaches the center position of the opening of sound emitting section 30 (i.e., the position where contact section 29 is provided). When the rod-shaped member has such a shape, the bonding force between the rod-shaped member and sound emitting section 30 increases, and displacement section 28 becomes more likely to bend in response to pressure changes inside housing 21.

[0046] The contact portion 29 is coupled to the displacement portion 28, and the elastic surface of the contact portion 29 comes into contact with a partial area of ​​the diaphragm 25. The contact portion 29 is provided, for example, at the center position of the displacement portion 28, and in the example shown in Fig. 5, is provided at a position where a plurality of rod-shaped members of the displacement portion 28 are coupled. The contact portion 29 has elasticity such that the surface is deformed when the inside of the housing 21 is depressurized and the diaphragm 25 is displaced toward the sound emitting portion 30 when the user removes the earphone 1 from the ear.

[0047] The contact portion 29 has a fluidity that forms a curved surface due to surface tension before hardening. The contact portion 29 is preferably formed of a resin that increases in elasticity with time and has elasticity after hardening. By forming the contact portion 29 from such a material, the contact portion 29 can be easily formed into a desired shape. Examples of such materials include, but are not limited to, nitrile rubber adhesives, synthetic rubber adhesives, vinyl adhesives, silicone rubber, and sponge. The contact portion 29 may be formed from the same material as the displacement portion 28, for example, or may be formed from ABS resin. By forming the contact portion 29 from a material having elasticity, the diaphragm 25 does not receive local stress from the contact portion 29, and the diaphragm 25 is less likely to be damaged.

[0048] Moreover, it is preferable that the amount of displacement of the tip of contact portion 29 when a predetermined stress in a direction in which diaphragm 25 is displaced is applied to contact portion 29 is greater than the amount of displacement of displacement portion 28 when the above-mentioned predetermined stress in a direction in which diaphragm 25 is displaced is applied to displacement portion 28. By configuring contact portion 29 in this manner, when diaphragm 25 is displaced toward sound emitting portion 30 due to a change in the internal pressure of housing 21, contact portion 29 deforms before displacement of displacement portion 28. This deformation of contact portion 29 reduces the stress applied to diaphragm 25.

[0049] Fig. 6 is a diagram showing an electric circuit of an acoustic system of the earphone 1. Fig. 6 shows a part of the electric circuit housed in the rear housing 12. Specifically, the rear housing 12 has a varistor 121 and a resonant circuit 122 connected between the terminal 24 of the electro-acoustic transducer 20 and the conductive member 27. The varistor 121 prevents an excessive voltage from being applied to the electro-acoustic transducer 20.

[0050] The resonant circuit 122 is a circuit that outputs an adjustment signal. The adjustment signal is a signal in which a signal component of a predetermined resonant frequency included in the electric signal output by the sound source device 2 is made larger than signal components of other frequencies. The resonant circuit 122 has, for example, a resistor 123, an inductor 124, and a capacitor 125 that configure a series resonant circuit. Specifically, the resonant circuit 122 has the resistor 123 and the inductor 124 that are connected in series with each other between the connection portion 10 and the diaphragm 25, and a capacitor 125 as an example of a capacitance circuit provided between the fixed pole 22 and the diaphragm 25.

[0051] In the earphone 1, the center of the diaphragm 25 is pressed against the fixed pole 22 by the contact portion 29, so the capacitance generated by the fixed pole 22 and the diaphragm 25 is larger than when the diaphragm 25 is not pressed against the fixed pole 22 by the contact portion 29. This configuration realizes that the capacitance generated by the fixed pole 22 and the diaphragm 25 can be set to, for example, 60 pF or more. In this case, the inductance value of the inductor 124 required to set the resonant frequency of the resonant circuit 122 to about 10 KHz is 2.0 H or less, and the size of the inductor 124 can be reduced.

[0052] As an example, when the electroacoustic transducer 20 has a capacitance of 120 pF and the varistor 121 has a capacitance of 130 pF, the resistance of the resistor 123 is set to 420 Ω, the inductance of the inductor 124 is set to 400 mH, and the capacitance of the capacitor 125 is set to 220 pF, so that the resonance frequency of the resonance circuit 122 is approximately 10 KHz. Note that, although Fig. 6 shows a case where the resonance circuit 122 is a series resonance circuit, the resonance circuit 122 is not limited to a series resonance circuit formed by the resistor 123, the inductor 124, and the capacitor 125, but may be a parallel resonance circuit or a circuit combining a series resonance circuit and a parallel resonance circuit. Note that the resonance frequency is not limited to 10 KHz, and the sensitivity at other frequencies can be adjusted by adjusting the characteristics of the resonance circuit 122.

[0053] Furthermore, by setting the capacitance value of the capacitor 125 to be sufficiently larger than the electrostatic capacitance value of the electroacoustic transducer 20 (for example, 10 times or more), the variation in the resonant frequency caused by the variation in the electrostatic capacitance value of the electroacoustic transducer 20 is suppressed.

[0054] Example [First Example] First, we measured the frequency characteristics of the sensitivity of the first earphone 1, which had the electroacoustic transducer 20 configured as shown in Figures 3 to 5 and did not have the resonant circuit 122. As a comparative example, we measured the frequency characteristics of the sensitivity of an earphone that did not have the resonant circuit 122, the displacement portion 28, and the contact portion 29.

[0055] Fig. 7 is a diagram showing the measurement results of the frequency characteristics of the sensitivity of an earphone 1 that does not have a resonant circuit 122. The horizontal axis of Fig. 7 is frequency, and the vertical axis is sensitivity. The solid line in Fig. 7 shows the frequency characteristics of the sensitivity of the earphone 1 that has the displacement portion 28 and the contact portion 29. The dashed line shows the frequency characteristics of the sensitivity of an earphone that does not have the displacement portion 28 and the contact portion 29.

[0056] 7, in the range of 1 kHz or less, the sensitivity of the earphone 1 having the displacement portion 28 and the contact portion 29 is about 5 dB to 10 dB better than the sensitivity of the earphone without the displacement portion 28 and the contact portion 29. This is because the elastic contact portion 29 presses the center of the diaphragm 25 against the fixed pole 22, so that the distance from the fixed pole 22 varies depending on the position of the diaphragm 25.

[0057] [Second Example] The results of comparing the second earphone 1 having the resonant circuit 122 together with the electroacoustic transducer 20 configured as shown in Figures 3 to 5 with the first earphone 1 are shown below. Figure 8 is a diagram showing the measurement results of the frequency characteristics of the earphone 1 having a series resonant circuit composed of the varistor 121, the resonant circuit 122, and the resistor 123.

[0058] 8 shows the frequency characteristic of the sensitivity of the earphone 1 having the resonant circuit 122 including a resistor 123 with a resistance value of 420 Ω, an inductor 124 with an inductance value of 400 mH, and a capacitor 125 with a capacitance value of 220 pF. The dashed line shows the frequency characteristic of the sensitivity of the earphone 1 without the resonant circuit 122. The dashed line shows the frequency characteristic of the sensitivity of the earphone 1 having a resonance sharpness lower than the resonance sharpness of the earphone 1 having the resonant circuit 122 shown by the solid line.

[0059] A comparison of the characteristics shown by the solid and dashed lines with those shown by the dashed lines shows that there is a large difference in sensitivity around 10 kHz. Specifically, the sensitivity around 10 kHz when the first series resonant circuit shown by the solid line is 15 dB higher than the sensitivity around 10 kHz when the first series resonant circuit is not included. In this way, by including the resonant circuit 122 in the earphone 1, the sensitivity in the frequency band below 1 kHz is improved, and the sensitivity around the resonant frequency of the resonant circuit 122 is also improved.

[0060] Also, the sensitivity at around 10 kHz when the first series resonant circuit shown by the solid line is different from the sensitivity at around 10 kHz when the second series resonant circuit shown by the dashed dotted line is about 10 dB different. In this way, by controlling the resonance sharpness of the series resonant circuit, it becomes easier to design earphones 1 with different sensitivities at around 10 kHz.

[0061] [First Modification of Resonant Circuit 122] Fig. 9 is a diagram showing a resonant circuit 122a which is a first modified example of the resonant circuit 122. The resonant circuit 122a shown in Fig. 9 has a capacitance circuit 126 whose capacitance value changes under the control of a control unit 127, instead of the capacitor 125 in the resonant circuit 122. The control unit 127 is, for example, a CPU (Central Processing Unit). The control unit 127 acquires setting information for setting the capacitance value of the capacitance circuit 126, and controls the capacitance value based on the acquired setting information. The control unit 127 acquires setting information inputted in the sound source device 2 which is executing an application program, and controls the capacitance value of the capacitance circuit 126 based on the acquired setting information, for example.

[0062] The capacitance circuit 126 is, for example, a variable capacitance diode whose capacitance value changes depending on the voltage input thereto. In this case, the control unit 127 applies a voltage corresponding to the acquired setting information to the capacitance circuit 126, thereby controlling the capacitance value of the capacitance circuit 126.

[0063] The capacitance circuit 126 may have a plurality of capacitors each having a different capacitance, and a switch for selecting a portion of the plurality of capacitors. In this case, the control unit 127 may control the capacitance value of the capacitance circuit 126 by switching the switch. In this way, the resonance circuit 122a is configured so that the capacitance value of the capacitance circuit 126 can be controlled by the control unit 127, and thus the resonance frequency of the resonance circuit 122a is changed by the control of the control unit 127. As a result, a user who uses the earphones 1 connected to the sound source device 2 can adjust the frequency characteristics of the sensitivity of the earphones 1 to desired characteristics.

[0064] [Second Modification of Resonant Circuit 122] FIG. 10 is a diagram showing a resonant circuit 122b which is a second modified example of the resonant circuit 122. The resonant circuit 122b shown in FIG. 9 has a capacitance circuit 128 instead of the capacitor 125 in the resonant circuit 122. The capacitance circuit 128 has capacitor connections C1 and C2 which connect the capacitor between the fixed pole and the diaphragm in a state in which the capacitor connected between the fixed pole and the diaphragm can be replaced. The capacitor connections C1 and C2 are conductive terminals and are exposed to the outside of the rear housing 12. The user of the earphone 1 can change the resonant frequency of the resonant circuit 122b by replacing the capacitor attached between the capacitor connection C1 and the capacitor connection C2 with a capacitor of a different capacity, thereby adjusting the frequency characteristic of the sensitivity of the earphone 1 to a desired characteristic.

[0065] 10 does not have the capacitor 125 shown in FIG 6, but may have the capacitor 125 in parallel with the capacitance circuit 128. When the resonance circuit 122b has such a configuration, the user need only attach a capacitor to the capacitance circuit 128 when it is desired to change the resonance frequency of the resonance circuit 122b.

[0066] [First Modification of the Electroacoustic Transducer 20] Figures 11 and 12 are diagrams showing the internal configuration of an electroacoustic transducer 20a which is a first modified example of the electroacoustic transducer 20. Figure 12 is a cross-sectional view taken along the line DD in Figure 11. In the electroacoustic transducer 20 shown in Figures 4 and 5, one end of the displacement section 28 is fixed to the position of the opening of the sound emitting section 30, whereas in the electroacoustic transducer 20a shown in Figures 11 and 12, a displacement section 31 is provided so as to face the entire surface of the diaphragm 25. The rod-shaped member of the displacement section 31 is longer than the rod-shaped member of the displacement section 28.

[0067] The displacement portion 31 is fixed so as to be sandwiched between the spacer 32 and the conductive member 27. The spacer 32 is an annular member, and is fixed to the inner surface of the housing 21. Since the spacer 32 has a thickness larger than the width of displacement of the displacement portion 31, the displacement portion 31 does not come into contact with the housing 21 even in the maximum displacement state. In this way, since the electroacoustic transducer 20a has the displacement portion 31 having a rod-shaped member longer than the displacement portion 28, when the pressure inside the electroacoustic transducer 20 changes and the diaphragm 25 is displaced, the displacement portion 31 is more likely to bend than the displacement portion 28. Therefore, the stress applied to the diaphragm 25 can be further reduced.

[0068] Furthermore, the rod-shaped member of the displacement portion 31 has a shape that, for example, becomes thinner as it approaches the position where the contact portion 29 is provided. By providing the rod-shaped member with such a shape, the peripheral edge portion of the displacement portion 31 is stably fixed, and the portion of the displacement portion 31 near the contact portion 29 is easily bent.

[0069] [Second Modification of the Electroacoustic Transducer 20] Fig. 13 is a diagram showing the internal configuration of an electroacoustic transducer 20b which is a second modified example of the electroacoustic transducer 20. The electroacoustic transducer 20b shown in Fig. 13 differs from the electroacoustic transducer 20 in that it has an electret layer 33, but other configurations are the same as those of the electroacoustic transducer 20. The electret layer 33 includes a dielectric material that semi-permanently holds an electric charge, and applies a bias voltage to the fixed pole 22.

[0070] The electret layer 33 is provided on a surface of the fixed electrode 22 facing the diaphragm 25. The peripheral edge of the diaphragm 25 is sandwiched between an annular insulating member 26 and a conductive member 27.

[0071] 13, the electret layer 33 is accommodated in a recess of the fixed pole cover 23 in a state where it is overlapped with the fixed pole 22. The electret layer 33 has a sound hole formed at the same position as the sound hole 221 formed in the fixed pole 22. The fixed pole 22 and the electret layer 33 are formed with a sound hole by, for example, punching in a state where they are overlapped. Since the electro-acoustic transducer 20b has the electret layer 33 in this way, it is not necessary to apply a DC bias voltage via an external amplifier or transformer, and usability for the user is improved.

[0072] [Third Modification of the Electroacoustic Transducer 20] Fig. 14 is a diagram showing the internal configuration of an electroacoustic transducer 20c which is a third modified example of the electroacoustic transducer 20. The electroacoustic transducer 20c has a displacement portion 31 which the electroacoustic transducer 20a shown in Fig. 11 has, instead of the displacement portion 28 which the electroacoustic transducer 20b has. The displacement portion 31 is sandwiched between a conductive member 27 and a spacer 32. As shown in the above first to third modified examples, the combination of the means for applying a bias voltage to the fixed pole 22 and the means for displacing the contact portion 29 is arbitrary.

[0073] [Modification of displacement portion 28] Fig. 15 is a diagram showing the shape of a displacement section 28a which is a modified example of the displacement section 28. The displacement section 28 shown in Fig. 5 is configured of a straight rod-shaped member, but the displacement section 28a includes a curved member that is longer than the radius of the sound emitting section 30. By including such a curved member in the displacement section 28a, the displacement section 28a can be displaced more than the displacement section 28 in the direction in which sound is emitted from the sound emitting section 30.

[0074] [Modification of the capacitive electroacoustic transducer] In the above description, the capacitive electroacoustic transducer is exemplified by a canal-type earphone 1, and the electroacoustic transducers 20, 20a, 20b, and 20c are provided in the canal-type earphone, but the capacitive electroacoustic transducer is not limited to the canal-type earphone 1. The capacitive electroacoustic transducer can be applied to any device that has the function of converting an electric signal into sound. For example, the capacitive electroacoustic transducer may be an overhead headphone.

[0075] [Effects of the electroacoustic transducer according to the present embodiment] As described above, the earphone 1 has the resonant circuit 122 in front of the electroacoustic transducers 20, 20a, 20b, and 20c. By having the resonant circuit 122 in the earphone 1, the sensitivity in the high frequency range can be easily increased, and therefore the earphone 1 according to this embodiment achieves miniaturization and a wide dynamic range by using the capacitor-type electroacoustic transducers 20, 20a, 20b, and 20c.

[0076] In particular, the electroacoustic transducers 20, 20a, 20b, and 20c have a structure in which the diaphragm 25 is pressed against the fixed pole 22 by the contact portion 29. Therefore, the earphone 1 according to this embodiment can have a capacitance value of 60 pF or more, which is larger than that of a conventional capacitor-type electroacoustic transducer. As a result, the inductance value of the inductor 124 of the resonant circuit 122 can be set to 10 mH or more and 2.0 H or less. Therefore, the electroacoustic transducers 20, 20a, 20b, and 20c can use inductors that are smaller in size than those of the conventional technology, and are therefore suitable for realizing a smaller earphone 1 and a wider dynamic range.

[0077] Furthermore, by providing the electroacoustic transducers 20, 20a, 20b, and 20c with a configuration in which the diaphragm 25 is pressed against the fixed electrode 22, the earphone 1 or headphones which are the capacitive electroacoustic transducer of this embodiment have a sensitivity improved by six times or more compared to conventional capacitive electroacoustic transducers. Instead of a high bias voltage exceeding 120V from an external power source or a large transformer that was necessary to increase the sensitivity in conventional capacitive electroacoustic transducers, the capacitive electroacoustic transducer of this embodiment can configure the earphone 1 or headphones with a bias voltage from an electret.

[0078] That is, earphones or headphones using conventional electrostatic electroacoustic transducers require special power supplies or transformers and amplifiers, making them unsuitable for outdoor use. In contrast, in the earphones 1 or headphones using the electrostatic electroacoustic transducer of this embodiment, a bias voltage is applied by the electret, so even a small transformer or amplifier can provide the volume required for music appreciation. Therefore, the earphones 1 or headphones of this embodiment have a configuration suitable for outdoor use.

[0079] Also, even in a configuration where a bias voltage is applied by an external power source, the bias voltage of the earphone 1 or headphone using the electrostatic electroacoustic converter of this embodiment can be supplied from the sound source device. In other words, since a large bias voltage as in the past is not required, a special power source for applying the bias voltage is also not required.

[0080] In this embodiment, these small transformers or amplifiers are stored in the connection unit 10, but they may be provided in the sound source device 2. In addition, when a wireless connection is used to connect the earphones 1 or headphones to the sound source device 2, the small transformers or amplifiers may be provided in a receiving unit provided in the earphones 1 or headphones.

[0081] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by distributing or integrating functionally or physically in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment resulting from the combination combines the effect of the original embodiment. [Explanation of symbols]

[0082] 1. Earphones 2 Sound source device 10 Connection 11 Cable 12 Rear housing 13 Front housing 14 Earpiece 15 Aperture 20 Electroacoustic transducer 21 Case 22 fixed pole 23 Fixed pole cover 24 terminals 25 Diaphragm 26 Insulating materials 27 Conductive materials 28 Displacement section 29 Contact Part 30 Sound emitting part 31 Displacement section 32 Spacer 33 Electret layer 121 Barista 122 Resonant circuit 123 Resistance 124 Inductor 125 Capacitor 126 Capacitive circuit 127 Control Unit 128 Capacitive circuit 221 sound hole 271 Circular section 272 Extension section

Claims

1. a resonant circuit that outputs an adjustment signal in which a signal component of a predetermined frequency included in the electrical signal output from the sound source device is made larger than signal components of other frequencies; A fixed pole fixed to a housing; a diaphragm provided opposite to the fixed electrode and vibrating in response to a potential difference generated between the diaphragm and the fixed electrode based on the adjustment signal; a contact portion that contacts a partial area of ​​the diaphragm and presses the partial area against the fixed pole; a sound emitting section that emits sound generated by the vibration of the diaphragm to the outside of the housing; A connection unit connected to the sound source device; having The resonant circuit comprises: a resistor and an inductor connected in series between the connection portion and the diaphragm; a capacitance circuit provided between the fixed electrode and the diaphragm; A capacitive electroacoustic transducer having the above structure.

2. a capacitance value of the capacitance circuit is 10 times or more a capacitance value of an electroacoustic transducer including the fixed pole, the diaphragm, the contact portion, and the sound emitting portion; 2. A capacitive electroacoustic transducer according to claim 1.

3. a control unit that acquires setting information for setting a capacitance value of the capacitance circuit and controls the capacitance value based on the acquired setting information; 3. A capacitive electroacoustic transducer according to claim 1 or 2.

4. the sound source device is an information terminal that executes an application program, the control unit acquires the setting information inputted in the information terminal on which the application program is being executed.

4. A capacitive electroacoustic transducer according to claim 3.

5. the capacitance circuit has a capacitor connection portion that connects the capacitor between the fixed pole and the diaphragm in a state in which the capacitor connected between the fixed pole and the diaphragm is interchangeable; 3. A capacitive electroacoustic transducer according to claim 1 or 2.

6. the capacitor connection portion is exposed to the outside of a housing of the capacitive electroacoustic transducer; 6. A capacitive electroacoustic transducer according to claim 5.

7. The capacitance generated by the fixed electrode and the diaphragm is 60 pF or more, The inductor has an inductance value of 2.0H or less.

7. A capacitive electroacoustic transducer according to claim 1.

8. The resonant frequency of the resonant circuit is 10 KHz.

8. A capacitive electroacoustic transducer according to claim 1.

9. a distance between the diaphragm and the fixed pole in a partial region of the diaphragm is narrower than a distance between the diaphragm and the fixed pole outside the partial region; 9. A capacitive electroacoustic transducer according to claim 1.

10. a distance between the diaphragm and the fixed pole at a central portion of the diaphragm is narrower than a distance between the diaphragm and the fixed pole outside the central portion of the diaphragm; 10. A capacitive electroacoustic transducer according to claim 9.

11. The distance between the diaphragm and the fixed pole becomes wider from the center of the diaphragm to the outer edge of the diaphragm.

11. A capacitive electroacoustic transducer according to claim 10.

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