Electrostatic capacitive electroacoustic transducer

Abstract

The earphone (1) comprises: a resonant circuit (122) which outputs an adjustment signal that makes the signal component of a predetermined resonant frequency contained in the electrical signal output by the sound source device (2) greater than the signal components of other frequencies; a fixed pole (22) which is fixed to the housing; a diaphragm (25) which is arranged opposite to the fixed pole (22) and vibrates according to the potential difference generated between the diaphragm and the fixed pole (22) based on the adjustment signal; a contact portion (29) which contacts a part of the diaphragm (25) and presses the part toward the side close to the fixed pole (22); and a sound emitting portion (30) which emits the sound generated by the vibration of the diaphragm (25) to the outside of the housing.

Description

Technical Field

[0001] The present invention relates to a capacitive-type electro-acoustic transducer for converting electrical signals into sounds. Background Art

[0002] An electrostatic capacitive electroacoustic transducer is known that converts electrical signals into sound by utilizing the vibration of a diaphragm generated by the electrical signal. Patent Document 1 discloses a magnetic-type earphone. In this magnetic-type earphone, current flows through a coil disposed within a magnetic circuit, changing the coil's attractive force and causing the diaphragm to vibrate, thereby generating sound.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-204844 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] Magnetic headphones have a narrow frequency band (i.e., dynamic range) over which they can reproduce sound. Therefore, to achieve a wider dynamic range, multiple units for bass, midrange, and treble must be combined. This results in a higher number of components compared to condenser headphones (electrostatic capacitance headphones), making miniaturization difficult.

[0008] On the other hand, to improve the sensitivity of capacitor headphones, the electrostatic capacitance must be increased, which requires a small distance between the diaphragm and the fixed pole. However, if the distance between the diaphragm and the fixed pole is too small, there is a problem that the diaphragm vibrates and contacts the fixed pole, causing a short circuit.

[0009] Therefore, the present invention has been made in view of these points, and an object of the present invention is to provide an electrostatic capacitance type electroacoustic transducer device capable of achieving a wider dynamic range and miniaturization.

[0010] Solutions for solving problems

[0011] The electrostatic capacitive electroacoustic transducer device of the present invention comprises: a resonant circuit that outputs an adjustment signal that makes a signal component of a specified frequency contained in an electrical signal output by a sound source device greater than signal components of other frequencies; a fixed pole that is fixed to a housing; a diaphragm that is arranged opposite to the fixed pole and vibrates according to a potential difference generated between the diaphragm and the fixed pole based on the adjustment signal; a contact portion that contacts a portion of the diaphragm to press the portion toward the fixed pole; and a sound emitting portion that emits sound generated by the vibration of the diaphragm to the outside of the housing.

[0012] Alternatively, the electrostatic capacitive electroacoustic transducer device further has a connection portion connected to the sound source device, and the resonant circuit has: a resistor and an inductor, the resistor and the inductor being connected in series with each other between the connection portion and the diaphragm; and a capacitor circuit, which is arranged between the fixed pole and the diaphragm.

[0013] The electrostatic capacitance value of the capacitance circuit may be 10 times or more higher than the electrostatic capacitance value of the electroacoustic transducer including the fixed electrode, the diaphragm, the contact portion, and the sound emitting portion.

[0014] Alternatively, the electrostatic capacitive electroacoustic transducer device may further include a control unit configured to acquire setting information for setting a capacitance value of the capacitance circuit and control the capacitance value based on the acquired setting information.

[0015] The sound source device may be an information terminal that executes an application program, and the control unit may acquire the setting information input into the information terminal while the application program is being executed.

[0016] The capacitance circuit may include a capacitor connecting portion configured to connect the capacitor between the fixed electrode and the diaphragm in a replaceable manner.

[0017] The capacitor connection portion may be exposed outside the housing of the electrostatic capacitive electroacoustic transducer.

[0018] The electrostatic capacitance generated by the fixed electrode and the diaphragm may be 60 pF or greater, and the inductance of the inductor may be 2.0 H or less.

[0019] Alternatively, the resonant frequency of the resonant circuit is 10 KHz.

[0020] The distance between the diaphragm and the fixed pole in a partial region of the diaphragm may be narrower than the distance between the diaphragm and the fixed pole in a region outside the partial region.

[0021] The distance between the diaphragm and the fixed pole in the center portion of the diaphragm may be narrower than the distance between the diaphragm and the fixed pole in an area outside the center portion of the diaphragm.

[0022] The distance between the diaphragm and the fixed electrode may increase from a central portion of the diaphragm toward an outer edge of the diaphragm.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to achieve a wider dynamic range and a smaller size of the electrostatic capacitance electroacoustic transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a diagram showing the structure of an electroacoustic transducer system S.

[0026] Figure 2 This is an enlarged view of earphone 1.

[0027] Figure 3 yes Figure 2 Cross-sectional view at line AA.

[0028] Figure 4 yes Figure 3 Cross-sectional view at line BB.

[0029] Figure 5 It is from Figure 4 The CC line is observed on the side of the earpiece 14.

[0030] Figure 6 1 is a diagram showing a circuit included in the earphone 1 .

[0031] Figure 7 1 is a graph showing the measurement results of the frequency characteristics of the sensitivity of the earphone 1 without a series resonant circuit.

[0032] Figure 8 1 is a graph showing the measurement results of the frequency characteristics of the sensitivity of the earphone 1 having a series resonant circuit.

[0033] Figure 9 1 is a diagram showing a resonance circuit 122 a as a first modification of the resonance circuit 122 .

[0034] Figure 10 1 is a diagram showing a resonant circuit 122 b as a second modification of the resonant circuit 122 .

[0035] Figure 11 2 is a diagram showing the internal structure of the electroacoustic transducer 20 a.

[0036] Figure 12 yes Figure 11Cross-sectional view at line DD.

[0037] Figure 13 2 is a diagram showing the internal structure of the electroacoustic transducer 20 b.

[0038] Figure 14 2 is a diagram showing the internal structure of the electroacoustic transducer 20 c.

[0039] Figure 15 2 is a diagram showing the shape of the displacement portion 28a. DETAILED DESCRIPTION

[0040] [Overview of Electroacoustic Transducer System S]

[0041] Figure 1 is a diagram showing the structure of an electroacoustic transducer system S. The electroacoustic transducer system S includes earphones 1 and a sound source device 2. The earphones 1 are an example of an electrostatic capacitance electroacoustic transducer device, and convert electrical signals output from the sound source device 2 into sound, and emit the sound externally.

[0042] The sound source device 2 is, for example, a smartphone, computer, or audio player that is an information terminal executing an application program, and outputs an electrical signal based on sound source data containing music, sounds, etc. The sound source device 2 may store the sound source data in a storage medium or obtain the sound source data from an external device via a communication line.

[0043] Figure 2 This is an enlarged view of earphone 1. Figure 2 (a) is a stereoscopic view of the earphone 1, Figure 2 (b) is a side view of earphone 1. Earphone 1 is, for example, an electret-type electrostatic capacitive electroacoustic transducer that converts electrical signals into sound by varying the capacitance between a fixed pole and a vibrating plate (also called a diaphragm). Therefore, earphone 1 includes a magnet for generating sound.

[0044] The earphone 1 includes a connecting portion 10, a cable 11, a rear shell 12, a front shell 13, and an earpiece 14. An opening 15 for emitting sound to the outside is formed at the front end of the earpiece 14.

[0045] The connecting portion 10 includes an amplifier that is connected to the sound output terminal of the sound source device 2 and amplifies the electrical signal output from the terminal. The sensitivity of the electrostatic capacitance type electroacoustic transducer is lower than that of the electric type (dynamic type), balanced armature type electroacoustic transducer, etc. Therefore, in the electrostatic capacitance type electroacoustic transducer, the electrical signal is amplified by the connecting portion 10 so that a volume suitable for music appreciation can be output. The amplifier may include a step-up transformer or an amplifier for signal amplification.

[0046] Cable 11 is used to transmit electrical signals supplied from a sound source. Rear housing 12 is located between cable 11 and front housing 13. Rear housing 12 includes electroacoustic transducer 20, which converts electrical signals transmitted via cable 11 into sound. Details of the internal structure of electroacoustic transducer 20 will be described later.

[0047] The front housing 13 is disposed between the rear housing 12 and the earpiece 14 and has a variable angle relative to the rear housing 12 .

[0048] The earpiece 14 is a portion of the earphone 1 that is inserted into the user's ear and is coupled to a sound guide tube protruding from the front housing 13. The earpiece 14 emits the sound generated by the electroacoustic transducer 20 from the opening 15.

[0049] [Detailed Structure of Electroacoustic Transducer 20]

[0050] Figures 3 to 5 is a schematic diagram showing the internal structure of the electroacoustic transducer 20 . Figure 3 yes Figure 2 Cross-sectional view at line AA. Figure 4 yes Figure 3 Cross-sectional view at line BB. Figure 5 It is from Figure 4 The CC line is observed on the side of the earpiece 14.

[0051] like Figures 3 to 5 As shown, the electroacoustic transducer 20 includes 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 .

[0052] The housing 21 is formed, for example, from resin and has a space for accommodating components that generate sound based on electrical signals supplied from a sound source. The housing 21 includes a sound emitting portion 30 communicating with this space. The sound emitting portion 30 emits the sound generated by the electrical signals to the outside through the earpiece 14. The sound emitting portion 30 is, for example, a cylindrical portion extending toward the earpiece 14. The housing 21 also functions as an exterior member for the rear housing 12.

[0053] The portion of the housing 21 that receives electrical signals is connected to the connector 10 via the cable 11, and the portion of the housing 21 that emits sound is connected to the receiver 14. Figures 3 to 5 In the illustrated example, the case where the housing 21 has a circular cross section is shown, but the shape of the housing 21 is arbitrary, and the housing 21 may have a polygonal cross section.

[0054] The fixed electrode 22 is formed of a flat conductive member (e.g., aluminum). The fixed electrode 22 generates an electric field between the fixed electrode 22 and the diaphragm 25 using an external electric field generated by, for example, an electret. Furthermore, an electrical signal input from a sound source is input to the fixed electrode 22 and the diaphragm 25 via a terminal 24 and a conductive member 27, respectively. Alternatively, the fixed electrode 22 may be replaced with an electret, and an electric field may be generated between the fixed electrode 22 and the diaphragm 25 by applying a bias voltage via the terminal 24.

[0055] The fixed pole 22 is fixed to the housing 21, for example, via 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 disc with a diameter of 20 mm. The fixed pole 22 is formed with a plurality of sound holes 221 for allowing the sound generated by the vibration of the diaphragm 25 to pass through.

[0056] The fixed pole cover 23 has a recess for accommodating the fixed pole 22. The fixed pole cover 23 is formed of an insulating member. Since the outer edge of the fixed pole 22 is surrounded by the insulating member, the fixed pole 22 is electrically insulated from the conductive member 27 described later.

[0057] Terminal 24 is a conductive terminal for supplying an electrical signal to fixed electrode 22. Terminal 24 is a first conductive portion connected to fixed electrode 22 and is located on the side of fixed electrode 22 opposite to the sound emitting portion 30. Terminal 24 is electrically coupled to fixed electrode 22. The electrical signal supplied from the sound source is superimposed on a bias voltage or the surface potential of the electret and then input through terminal 24.

[0058] The diaphragm 25 is provided facing the fixed electrode 22 and is a vibration plate that vibrates in response to an electrical signal supplied from a sound source. The diaphragm 25 is formed of a conductive thin film, such as metal foil or a polymer film on which gold is deposited.

[0059] The diaphragm 25 vibrates in response to a potential difference generated by an electrical signal supplied from the sound source device 2. Specifically, the diaphragm 25 vibrates in response to a potential difference generated between the diaphragm 25 and the fixed pole 22 in response to an electrical signal applied via the terminal 24 and the conductive member 27. More specifically, the diaphragm 25 vibrates in response to a potential difference generated between the diaphragm 25 and the fixed pole 22 in response to an adjustment signal, the frequency characteristics of which have been adjusted by a resonant circuit 122 (described later).

[0060] The contact portion 29 is used to move a portion of the diaphragm 25 (at Figure 4 In the example shown, the central portion is pressed toward the side close to the fixed pole 22, and the gap between the diaphragm 25 and the fixed pole 22 in a certain area is narrower than the gap between the diaphragm 25 and the fixed pole 22 in the outer area of the certain area. Figure 4In the example shown, the distance between the diaphragm 25 and the fixed pole 22 increases as it moves from the center of the diaphragm 25 toward the outer edge of the diaphragm 25. Due to the pressure applied by the contact portion 29, the diaphragm 25 contacts the fixed pole 22 in a portion of the area. By configuring the diaphragm 25 in this manner, the distance between the diaphragm 25 and the fixed pole 22 varies depending on the position of the diaphragm 25, thereby improving the sensitivity of the electroacoustic transducer 20 to electrical signals over a wide frequency range.

[0061] In addition, since the distance between at least a portion of the diaphragm 25 and the fixed pole 22 can be reduced, the electrostatic capacitance of the electroacoustic transducer 20 is increased. Since the electrostatic capacitance of the electroacoustic transducer 20 is increased, the inductance value of the inductor constituting the resonant circuit 122 described later can be reduced. In addition, such a structure helps to reduce the signal amplification performed by the connecting portion 10. In order to output a volume sufficient for music appreciation, conventional electrostatic electroacoustic transducers must significantly amplify the electrical signal. A structure that shortens the distance between the fixed pole and a portion of the vibration plate can reduce the amplification of the electrical signal, thereby making it possible to reduce the size of the step-up transformer and amplifier.

[0062] The insulating member 26 is provided to prevent electrical conduction between the diaphragm 25 and the fixed electrode 22 and is formed, for example, from a resin. The insulating member 26 may be entirely formed from an insulating member, or at least one of the surface of the insulating member 26 that contacts the fixed electrode 22 and the surface of the insulating member 26 that contacts the diaphragm 25 may be insulating.

[0063] The insulating member 26 has, for example, an annular shape and is sandwiched between the peripheral edge of the diaphragm 25 and the fixed pole 22. As a result, the peripheral edge of the diaphragm 25 is fixed without contacting the fixed pole 22, and the region of the diaphragm 25 not in contact with the insulating member 26 vibrates according to the electrical signal.

[0064] The conductive member 27 is used to apply an electrical signal to the diaphragm 25. The conductive member 27 is a second conductive portion, and the portion of the conductive member 27 that is closer to the sound emitting portion 30 relative to the fixed pole 22 is connected to the diaphragm 25. The conductive member 27 is formed, for example, from a conductive sheet. The conductive member 27 includes an annular portion 271 that contacts the periphery of the diaphragm 25, and an extension portion 272 that extends from at least a portion of the annular portion 271 to the side opposite the sound emitting portion 30 relative to the fixed pole 22. The extension portion 272 extends between the housing 21, the fixed pole cover 23, and the insulating member 26, and extends to one side of the rear housing 12.

[0065] The displacement portion 28 and the contact portion 29 constitute a support portion that supports a portion of the diaphragm 25 toward the fixed pole 22, thereby applying pressure to the portion of the diaphragm 25. The displacement portion 28 is formed, for example, from a rod-shaped elastic resin, spring, or rubber, and is displaced in the direction in which the diaphragm 25 is displaced in response to changes in pressure within the housing 21. Specifically, when the diaphragm 25 is displaced in response to changes in pressure within the housing 21 that occur when the earpiece 14, which is part of the housing of the earphone 1, is worn or removed from a person's ear, the displacement portion 28 is subjected to the stress generated by the displacement of the diaphragm 25, causing it to displace.

[0066] exist Figure 5 In the example shown, the displacement portion 28 is provided at a position that crosses the sound emitting portion 30. The displacement portion 28 includes one or more rod-shaped members that cross the sound emitting portion 30. Specifically, the displacement portion 28 includes a plurality of rod-shaped members, one end of which is fixed to the opening of the sound emitting portion 30. Figure 5 In the example shown, three rod-shaped members extending in different directions at intervals of 120 degrees from the opening of the sound emitting portion 30 on the diaphragm 25 side are connected at the center of the sound emitting portion 30. However, the extending directions and number of the rod-shaped members are arbitrary.

[0067] The rod-shaped member included in the displacement portion 28 may be formed by integral molding with the housing 21 , or a rod-shaped member separate from the housing 21 may be fixed to the housing 21 using an adhesive or the like. Figure 5 The rod-shaped member shown has a uniform thickness, but it may also be tapered toward the center of the opening of the sound emitting portion 30 (i.e., where the contact portion 29 is located). This shape increases the coupling force between the rod-shaped member and the sound emitting portion 30, and also makes it easier for the displacement portion 28 to warp in response to pressure changes within the housing 21.

[0068] The contact portion 29 is combined with the displacement portion 28, and the elastic surface of the contact portion 29 contacts a portion of the diaphragm 25. The contact portion 29 is, for example, provided at the center of the displacement portion 28. Figure 5 In the example shown, the contact portion 29 is provided at the junction of the plurality of rod-shaped members included in the displacement portion 28. The contact portion 29 has elasticity such that when the user removes the earphone 1 from the ear, the pressure inside the housing 21 is reduced, causing the diaphragm 25 to displace toward the sound emitting portion 30 and deform its surface.

[0069] The contact portion 29 has fluidity that forms a curved surface due to surface tension before solidification. Preferably, the contact portion 29 is formed of a resin whose elasticity increases with time and has elasticity after solidification. The contact portion 29 is formed of such a material, whereby the contact portion 29 is easily formed into a desired shape. Examples of such materials include nitrile rubber-based adhesives, synthetic rubber-based adhesives, vinyl-based adhesives, silicone rubber, and sponges, but the materials are not limited thereto. The contact portion 29 can be formed of, for example, the same material as the displacement portion 28, or can be formed of ABS resin. The contact portion 29 is formed of a material having elasticity, whereby the diaphragm 25 is not locally subjected to stress from the contact portion 29, and therefore the diaphragm 25 is not easily damaged.

[0070] Furthermore, it is preferable that the amount of displacement of the tip of contact portion 29 when a predetermined stress in the direction in which diaphragm 25 is displaced is greater than the amount of displacement of displaced portion 28 when the predetermined stress in the direction in which diaphragm 25 is displaced is applied to displaced portion 28. By configuring contact portion 29 in this manner, when diaphragm 25 is displaced toward sound emitting portion 30 due to changes in the internal pressure of housing 21, contact portion 29 deforms before displaced portion 28 is displaced. This deformation of contact portion 29 reduces the stress applied to diaphragm 25.

[0071] Figure 6 1 is a diagram showing a circuit of an audio system included in the headphones 1 . Figure 6 The figure shows a portion of the circuit housed in the rear case 12. Specifically, the rear case 12 includes a piezoresistor 121 and a resonant circuit 122 connected between the terminal 24 of the electroacoustic transducer 20 and the conductive member 27. The piezoresistor 121 prevents excessive voltage from being applied to the electroacoustic transducer 20.

[0072] The resonant circuit 122 is a circuit that outputs an adjustment signal. The adjustment signal is a signal that increases the signal component at a predetermined resonant frequency contained in the electrical signal output by the sound source device 2 relative to signal components at other frequencies. The resonant circuit 122 includes, for example, a resistor 123, an inductor 124, and a capacitor 125 forming a series resonant circuit. Specifically, the resonant circuit 122 includes the resistor 123 and the inductor 124 connected in series between the connecting portion 10 and the diaphragm 25, and the capacitor 125, which serves as an example of a capacitive circuit, disposed between the fixed electrode 22 and the diaphragm 25.

[0073] In earphone 1, the center portion of diaphragm 25 is pressed against fixed pole 22 via contact portion 29. Therefore, the electrostatic capacitance generated between fixed pole 22 and diaphragm 25 is greater than when the diaphragm 25 is not pressed against fixed pole 22 via contact portion 29. This structure enables the electrostatic capacitance generated between fixed pole 22 and diaphragm 25 to be set to, for example, 60 pF or greater. In this case, the inductance of inductor 124, required to achieve a resonant frequency of approximately 10 kHz in resonant circuit 122, is reduced to 2.0 H or less, thereby miniaturizing inductor 124.

[0074] For example, when the electrostatic capacitance of the electroacoustic transducer 20 is 120 pF and the electrostatic capacitance of the varistor 121 is 130 pF, the resonant frequency of the resonant circuit 122 becomes approximately 10 kHz by setting the resistance value of the resistor 123 to 420 Ω, the inductance value of the inductor 124 to 400 mH, and the capacitance value of the capacitor 125 to 220 pF. Figure 6 While resonant circuit 122 is shown as a series resonant circuit, it is not limited to a series resonant circuit consisting of resistor 123, inductor 124, and capacitor 125. It may also be a parallel resonant circuit or a combination of a series resonant circuit and a parallel resonant circuit. Furthermore, the resonant frequency is not limited to 10 kHz; by adjusting the characteristics of resonant circuit 122, sensitivity at other frequencies can be adjusted.

[0075] Furthermore, by setting the capacitance value of the capacitor 125 sufficiently larger than the electrostatic capacitance value of the electroacoustic transducer 20 (for example, 10 times or more), variations in the resonance frequency due to variations in the electrostatic capacitance value of the electroacoustic transducer 20 can be suppressed.

[0076] Embodiment [First embodiment]

[0077] First, the Figures 3 to 5 The frequency characteristics of sensitivity of the first earphone 1 having the electroacoustic transducer 20 of the structure shown and without the resonant circuit 122. As a comparative example, the frequency characteristics of sensitivity of an earphone without the resonant circuit 122, the displacement portion 28, and the contact portion 29 were measured.

[0078] Figure 7 1 is a diagram showing the measurement results of the frequency characteristics of the sensitivity of the earphone 1 without the resonant circuit 122 . Figure 7 The horizontal axis is frequency and the vertical axis is sensitivity. Figure 7 The solid line in represents the frequency characteristic of the sensitivity of the earphone 1 having the displacement portion 28 and the contact portion 29. The dotted line represents the frequency characteristic of the sensitivity of the earphone not having the displacement portion 28 and the contact portion 29.

[0079] from Figure 7It is clear that, in the frequency range below 1 kHz, the sensitivity of the earphone 1 having the displacement portion 28 and the contact portion 29 is approximately 5 dB to 10 dB higher than that 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 toward the fixed pole 22, causing the distance between the diaphragm 25 and the fixed pole 22 to vary depending on the position of the diaphragm 25.

[0080] [Second embodiment]

[0081] The following shows that Figures 3 to 5 The results are obtained by comparing the second earphone 1 having the electroacoustic transducer 20 of the structure shown and the resonant circuit 122 with the first earphone 1. Figure 8 1 is a diagram showing the measurement results of the frequency characteristics of the earphone 1 including the series resonant circuit composed of the varistor 121 , the resonant circuit 122 , and the resistor 123 .

[0082] Figure 8 The solid line in FIG. 1 shows the frequency characteristics of the sensitivity of the earphone 1 having a resonant circuit 122 comprising a resistor 123 having a resistance value of 420Ω, an inductor 124 having an inductance value of 400mH, and a capacitor 125 having a capacitance value of 220pF. The dashed line shows the frequency characteristics of the sensitivity of the earphone 1 without the resonant circuit 122. The dashed-dotted line shows the frequency characteristics of the sensitivity of the earphone 1 having a smaller resonance sharpness than the resonance sharpness of the earphone 1 having the resonant circuit 122 shown by the solid line.

[0083] Comparing the characteristics shown by the solid and dashed lines with the characteristics shown by the dotted line reveals a significant difference in sensitivity around 10 kHz. Specifically, the sensitivity around 10 kHz shown by the solid line, when the first series resonant circuit is included, is at least 15 dB higher than the sensitivity around 10 kHz when the first series resonant circuit is not included. Thus, the inclusion of resonant circuit 122 in earphones 1 improves sensitivity in the frequency band below 1 kHz, and also improves sensitivity near the resonant frequency of resonant circuit 122.

[0084] Furthermore, the sensitivity around 10 kHz for the case with the first series resonant circuit, shown by the solid line, differs by approximately 10 dB from the sensitivity around 10 kHz for the case with the second series resonant circuit, shown by the dashed-dotted line. By controlling the resonance sharpness of the series resonant circuit in this manner, it becomes easier to design earphones 1 with different sensitivities around 10 kHz.

[0085] [First Modification of Resonance Circuit 122]

[0086] Figure 9 1 is a diagram showing a resonance circuit 122 a as a first modification of the resonance circuit 122 . Figure 9The resonant circuit 122a shown includes a capacitor circuit 126 whose capacitance value changes under the control of a control unit 127, in place 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 capacitor circuit 126 and controls the capacitance value based on the acquired setting information. For example, the control unit 127 acquires setting information input into the sound source device 2 during the execution of an application program and controls the capacitance value of the capacitor circuit 126 based on the acquired setting information.

[0087] The capacitor circuit 126 is, for example, a variable capacitance diode whose capacitance value changes according to an input voltage. In this case, the control unit 127 controls the capacitance value of the capacitor circuit 126 by applying a voltage corresponding to the acquired setting information to the capacitor circuit 126.

[0088] Capacitor circuit 126 may also include multiple capacitors with varying capacitances and a switch for selecting a portion of the multiple capacitors. In this case, control unit 127 may control the capacitance value of capacitor circuit 126 by switching the switch. In this manner, resonant circuit 122a is configured such that the capacitance value of capacitor circuit 126 can be controlled by control unit 127. The resonant frequency of resonant circuit 122a thus changes in accordance with control by control unit 127. As a result, a user using headphones 1 connected to sound source device 2 can adjust the frequency characteristics of the sensitivity of headphones 1 to a desired characteristic.

[0089] [Second Modification of Resonance Circuit 122]

[0090] Figure 10 1 is a diagram showing a resonant circuit 122 b as a second modification of the resonant circuit 122 . Figure 9 The resonant circuit 122b shown has a capacitor circuit 128 in place of the capacitor 125 in the resonant circuit 122. The capacitor circuit 128 has capacitor connectors C1 and C2, which connect a capacitor between the fixed electrode and the diaphragm in a manner that allows the capacitor to be replaced with the capacitor connected between the fixed electrode and the diaphragm. The capacitor connectors C1 and C2 are conductive terminals exposed to the outside of the rear housing 12. The user of the earphones 1 can change the resonant frequency of the resonant circuit 122b by replacing the capacitor connected between the capacitor connectors C1 and C2 with a capacitor of a different capacitance, thereby adjusting the frequency characteristics of the sensitivity of the earphones 1 to the desired characteristics.

[0091] also, Figure 10 The resonant circuit 122b shown does not have Figure 6The capacitor 125 shown is not provided, but the capacitor 125 may be connected in parallel with the capacitance circuit 128. When the resonance circuit 122b has such a structure, the user can simply attach a capacitor to the capacitance circuit 128 when he or she wants to change the resonance frequency of the resonance circuit 122b.

[0092] [First Modification of the Electroacoustic Transducer 20]

[0093] Figure 11 and Figure 12 2 is a diagram showing the internal structure of an electro-acoustic transducer 20 a as a first modification of the electro-acoustic transducer 20 . Figure 12 yes Figure 11 Cross-sectional view at line DD. Figure 4 and Figure 5 In the electroacoustic transducer 20 shown in FIG. 1 , one end of the displacement portion 28 is fixed to the opening of the sound emitting portion 30. Figure 11 and Figure 12 In the electroacoustic transducer 20a shown, a displacement portion 31 is provided so as to face the entire surface of the diaphragm 25. The rod-shaped member included in the displacement portion 31 is longer than the rod-shaped member included in the displacement portion 28.

[0094] The displacement portion 31 is fixed so as to be sandwiched between the gasket 32 and the conductive member 27. The gasket 32 is an annular member fixed to the inner surface of the housing 21. The gasket 32 has a thickness greater than the amplitude of displacement of the displacement portion 31, so that the displacement portion 31 does not contact the housing 21 even when it is at its maximum displacement. Thus, the electroacoustic transducer 20a includes the displacement portion 31, which is a rod-shaped member longer than the displacement portion 28. As a result, when the pressure inside the electroacoustic transducer 20 changes and the diaphragm 25 displaces, the displacement portion 31 is more likely to warp than the displacement portion 28. This further reduces the stress applied to the diaphragm 25.

[0095] Furthermore, the rod-shaped member of the displacement portion 31 has a shape that becomes thinner as it approaches the position where the contact portion 29 is provided. This shape of the rod-shaped member stabilizes the periphery of the displacement portion 31 and makes it easier for the displacement portion 31 near the portion where the contact portion 29 is provided to warp.

[0096] [Second Modification of Electroacoustic Transducer 20]

[0097] Figure 13 2 is a diagram showing the internal structure of an electro-acoustic transducer 20 b as a second modification of the electro-acoustic transducer 20 . Figure 13The electroacoustic transducer 20b shown differs from the electroacoustic transducer 20 in that it has an electret layer 33 , but otherwise has the same structure as the electroacoustic transducer 20 . The electret layer 33 includes a dielectric that semi-permanently holds electric charge, and applies a bias voltage to the fixed electrode 22 .

[0098] The electret layer 33 is provided on the surface of the fixed electrode 22 that faces the diaphragm 25 . The peripheral edge of the diaphragm 25 is sandwiched between the annular insulating member 26 and the conductive member 27 .

[0099] exist Figure 13 In the example shown, the electret layer 33 is housed in a recessed portion of the fixed pole cover 23 while overlapping the fixed pole 22. A sound hole is formed in the electret layer 33 at the same position as the sound hole 221 formed in the fixed pole 22. The sound hole is formed by, for example, punching the fixed pole 22 and the electret layer 33 while they are overlapped. This electroacoustic transducer 20b, incorporating the electret layer 33, eliminates the need for applying a DC bias voltage via an external amplifier or transformer, improving user convenience.

[0100] [Third Modification of Electroacoustic Transducer 20]

[0101] Figure 14 2 is a diagram showing the internal structure of an electroacoustic transducer 20c as a third modified example of the electroacoustic transducer 20. The electroacoustic transducer 20c has Figure 11 The electroacoustic transducer 20a shown in the figure has a displacement portion 31 instead of the displacement portion 28 of the electroacoustic transducer 20b. The displacement portion 31 is sandwiched between the conductive member 27 and the spacer 32. As shown in the first to third modifications above, the combination of the means for applying a bias voltage to the fixed electrode 22 and the means for displacing the contact portion 29 is arbitrary.

[0102] [Modification of the displacement portion 28]

[0103] Figure 15 1 and 2 are diagrams showing the shape of a displacement portion 28 a as a modified example of the displacement portion 28 . Figure 5 The displacement portion 28 shown is composed of a straight rod-shaped member, but the displacement portion 28a is composed of a curved member having a radius longer than that of the sound emitting portion 30. By including such a curved member, the displacement portion 28a can be displaced more greatly than the displacement portion 28 in the direction in which sound is emitted from the sound emitting portion 30.

[0104] [Modification of the electrostatic capacitance electroacoustic transducer]

[0105] In the above description, an in-ear headphone 1 is used as an example of a capacitive electroacoustic transducer device, and the electroacoustic transducers 20, 20a, 20b, and 20c are provided in the in-ear headphone. However, the capacitive electroacoustic transducer device is not limited to the in-ear headphone 1. The capacitive electroacoustic transducer device can be applied to any device as long as it has the function of converting electrical signals into sound. For example, the capacitive electroacoustic transducer device can also be an overhead headphone.

[0106] [Effects of the Electroacoustic Transducer According to the Present Embodiment]

[0107] As described above, the earphone 1 includes the resonant circuit 122 in the preceding stage of the electroacoustic transducers 20, 20a, 20b, and 20c. The resonant circuit 122 easily improves sensitivity in the high-frequency range of the earphone 1. Therefore, the earphone 1 according to this embodiment achieves both miniaturization and a wider dynamic range due to the capacitor-type electroacoustic transducers 20, 20a, 20b, and 20c.

[0108] In particular, electroacoustic transducers 20, 20a, 20b, and 20c have a structure in which the diaphragm 25 is pressed against the fixed pole 22 via the contact portion 29. Therefore, the headphone 1 according to this embodiment can achieve a capacitance value of 60 pF or greater, which is greater than that of conventional capacitor-type electroacoustic transducers. Consequently, the inductance of inductor 124 included in resonant circuit 122 can be set to a value between 10 mH and 2.0 H. Consequently, electroacoustic transducers 20, 20a, 20b, and 20c can employ smaller inductors than conventional technologies, making them suitable for achieving miniaturization and a wider dynamic range in the headphone 1.

[0109] Furthermore, the electroacoustic transducers 20, 20a, 20b, and 20c have a structure that presses the diaphragm 25 toward the fixed pole 22. As a result, the earphones 1 or headphones, which are electrostatic capacitive electroacoustic transducers of this embodiment, have a sensitivity that is more than six times greater than that of conventional electrostatic capacitive electroacoustic transducers. Instead of requiring an external power supply or a large transformer to generate a high bias voltage exceeding 120V, which is required to increase sensitivity in conventional electrostatic capacitive electroacoustic transducers, the electrostatic capacitive electroacoustic transducer of this embodiment can utilize the bias voltage generated by the electret to form the earphones 1 or headphones.

[0110] That is, conventional earphones or headphones using electrostatic electroacoustic transducers require a special power supply or transformer and amplifier, making them unsuitable for outdoor use. In contrast, the earphones 1 or headphones using the electrostatic electroacoustic transducer of this embodiment utilize an electret to apply a bias voltage, allowing them to achieve the volume required for music appreciation using a compact transformer and amplifier. Therefore, the earphones 1 or headphones of this embodiment have a structure suitable for outdoor use.

[0111] Furthermore, in a configuration where the bias voltage is applied using an external power supply, the bias voltage for the earphones 1 or headphones using the electrostatic electroacoustic transducer of this embodiment can also be supplied from the sound source device. This eliminates the need for a conventionally high bias voltage and, consequently, eliminates the need for a special power supply for bias voltage application.

[0112] In this embodiment, these small transformers or amplifiers are housed in the connection portion 10. However, the sound source device 2 may also include these small transformers or amplifiers. Furthermore, if a wireless connection is used between the earphones 1 or headphones and the sound source device 2, the small transformers or amplifiers may be located in the receiving portion of the earphones 1 or headphones.

[0113] While the present invention has been described above using embodiments, the scope of protection of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes can be made within the scope of its main purpose. For example, all or part of the device can be functionally or physically dispersed or integrated in any unit. In addition, new embodiments generated by any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments generated by the combination have the effects of the original embodiments.

[0114] Description of Reference Numerals

[0115] 1: Headphones; 2: Sound source device; 10: Connecting portion; 11: Cable; 12: Rear shell; 13: Front shell; 14: Earpiece; 15: Opening; 20: Electroacoustic transducer; 21: Shell; 22: Fixed pole; 23: Fixed pole cover; 24: Terminal; 25: Diaphragm; 26: Insulating member; 27: Conductive member; 28: Displacement portion; 29: Contact portion; 30: Sound emission portion; 31: Displacement portion; 32: Gasket; 33: Electret layer; 121: Varistor; 122: Resonant circuit; 123: Resistor; 124: Inductor; 125: Capacitor; 126: Capacitive circuit; 127: Control unit; 128: Capacitive circuit; 221: Sound hole; 271: Annular portion; 272: Extension portion.

Claims

1. An electrostatic capacitive electroacoustic transducer device, comprising: a resonant circuit that outputs an adjustment signal that causes a signal component of a predetermined frequency included in the electrical signal output by the sound source device to be greater than signal components of other frequencies; a fixed pole fixed to the housing; a diaphragm formed of a conductive thin film and disposed facing the fixed electrode, and vibrating in response to a potential difference generated between the diaphragm and the fixed electrode based on the adjustment signal applied to a surface of the diaphragm opposite to the surface facing the fixed electrode; an electret layer, which is provided on the surface of the fixed electrode facing the diaphragm and applies a voltage to the fixed electrode; a contact portion that contacts a portion of the diaphragm and presses the portion toward the fixed pole; and A sound emitting portion emits sound generated by the vibration of the diaphragm to the outside of the housing.

2. The electrostatic capacitive electroacoustic transducer according to claim 1, wherein: It also has a connection portion connected to the sound source device, The resonant circuit has: a resistor and an inductor connected in series with each other between the connecting portion and the diaphragm; and A capacitor circuit is arranged between the fixed electrode and the diaphragm.

3. The electrostatic capacitive electroacoustic transducer according to claim 2, wherein: The electrostatic capacitance value of the capacitance circuit is 10 times or more greater than the electrostatic capacitance value of the electroacoustic transducer including the fixed electrode, the diaphragm, the contact portion, and the sound emitting portion.

4. The electrostatic capacitive electroacoustic transducer according to claim 2 or 3, wherein: The device further includes 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.

5. The electrostatic capacitive electroacoustic transducer according to claim 4, wherein: The sound source device is an information terminal that executes an application program. The control unit acquires the setting information input into the information terminal while the application is being executed.

6. The electrostatic capacitive electroacoustic transducer according to claim 2 or 3, wherein: The capacitance circuit includes a capacitor connecting portion that connects the capacitor between the fixed electrode and the diaphragm in a state where the capacitor connected between the fixed electrode and the diaphragm can be replaced with the capacitor.

7. The electrostatic capacitive electroacoustic transducer according to claim 6, wherein: The capacitor connection portion is exposed outside the housing of the electrostatic capacitance type electroacoustic transducer device.

8. The electrostatic capacitive electroacoustic transducer according to claim 2 or 3, wherein: The electrostatic capacitance generated by the fixed electrode and the diaphragm is 60 pF or more. The inductance of the inductor is less than 2.0H.

9. The electrostatic capacitive electroacoustic transducer according to claim 1 or 2, wherein: The resonant frequency of the resonant circuit is 10 KHz.

10. The electrostatic capacitive electroacoustic transducer according to claim 1 or 2, wherein: 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 in a region outside the partial region.

11. The electrostatic capacitive electroacoustic transducer according to claim 10, wherein: The distance between the diaphragm and the fixed pole in the central portion of the diaphragm is narrower than the distance between the diaphragm and the fixed pole in an area outside the central portion of the diaphragm.

12. The electrostatic capacitive electroacoustic transducer according to claim 11, wherein: The distance between the diaphragm and the fixed electrode increases from the center of the diaphragm toward the outer edge of the diaphragm.

13. An electrostatic capacitance electroacoustic transducer device comprising: a resonant circuit that outputs an adjustment signal that causes a signal component of a predetermined frequency included in the electrical signal output by the sound source device to be greater than signal components of other frequencies; a fixed pole fixed to the housing; a diaphragm formed of a conductive thin film and disposed facing the fixed electrode, and vibrating in response to a potential difference generated between the diaphragm and the fixed electrode based on the adjustment signal applied to a surface of the diaphragm opposite to the surface facing the fixed electrode; a contact portion that contacts a portion of the diaphragm on an elastic surface and presses the portion toward the fixed pole; and A sound emitting portion emits sound generated by the vibration of the diaphragm to the outside of the housing.

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