Abstract: An electret condenser microphone reinforces electrostatic discharge protection and noise isolation by adding a series of components in the electret condenser microphone. It is possible to block TDMA noise by embodying an RC circuit using series resistors and a varistor having a capacitor component in an electret condenser microphone, and to provide ESD protection effect when testing air or contact ESD by mounting two transient voltage suppressor (TVS) diodes. It is possible to block RF noises in various frequency bands, and to reduce TDMA noise level when making a cal with a maximum power level, by applying an electret condenser microphone for ESD protection and noise isolation to a mobile communication terminal. Further, since the electret condenser microphone may use an internal analog ground, an artwork of a PCB substrate or isolations from other parts is possible.

Abstract: A microphone preamplifier, comprising a differential input (102) stage with a first and a second input terminal and an output stage with an output terminal; where the microphone preamplifier is integrated on a semiconductor substrate. A feedback circuit, with a low-pass frequency transfer function (103), is coupled between the output terminal and the first input terminal and integrated on the semiconductor substrate. The second input terminal provides an input for a microphone signal (105). Thereby a very compact (with respect to consumed area of the semiconductor substrate), low noise preamplifier is provided.

Abstract: An apparatus comprising a capacitive transducer, for example a MEMS microphone. A first voltage generator is connected to receive a first voltage (VDD*) and generate a second voltage (VCP) for biasing the capacitive transducer. A control circuit is adapted to, in use, control the first voltage (VDD*) based on a calibration value, wherein a different calibration value would lead to a different first voltage level and the calibration value is set such that an input signal of known amplitude produces an output signal of predetermined amplitude.

Abstract: Electro-dynamic loudspeakers typically include a diaphragm having a conductor applied to one of its surfaces where the diaphragm is secured to a frame. The conductor is connected to a power supply for providing electrical current through linear traces of the conductor that interact with magnetic fields generated by magnets that are mounted to the frame. The diaphragm is driven by a motive force created when current passes through the conductor within the magnetic field. The electrical current is varied to create an acoustical output from the electro-dynamic loudspeaker. Different methods of attaching the diaphragm are provided for simplifying the manufacturing process and for obtaining a robust electro-dynamic loudspeaker.

Abstract: An acoustic signal processing apparatus includes an acoustic signal input device, a frequency resolution device, a two-dimensional data generating device, a graphics detection device, a sound source candidate information generating device, and a sound source information generating device. The sound source information generating device generates sound source information including at least one of the number of sound sources, the spatial existence range of the sound source, an existence period of the voice, a frequency component configuration of the voice, amplitude information on the voice, and symbolic contents of the voice based on the sound source candidate information and corresponding information which are generated by the sound source candidate information generating device.

Abstract: Disclosed is an electret condenser microphone which reinforces electrostatic discharge protection and noise isolation by adding a series of components in the electret condenser microphone. According to the present invention, it is possible to block TDMA noise by embodying an RC circuit using series resistors and a varistor having a capacitor component in an electret condenser microphone, and to provide ESD protection effect when testing air or contact ESD by mounting two transient voltage suppressor (TVS) diodes. It is possible to block RF noises in various frequency bands, and to reduce TDMA noise level when making a call with a maximum power level, by applying an electret condenser microphone for ESD protection and noise isolation to a mobile communication terminal. Further, since the electret condenser microphone according to the invention uses an internal analog ground, an artwork of a PCB substrate or isolations from other parts is possible.

Abstract: The present invention provides a condenser microphone having a proximity sensor consisting of an infrared light emitting diode and an infrared photodetector, the condenser microphone preventing the occurrence of noise and the malfunctioning of the infrared photodetector when the infrared light emitting diode is lighted using an AC component. Specifically, the present invention provides a condenser microphone operated using a predetermined DC power source; an infrared light emitting diode 20 is lighted at a predetermined frequency by an oscillation circuit 22 using an AC component, and a microphone output is turned on and off by an output signal from the infrared photodetector 21 which is tuned to the predetermined frequency. The condenser microphone further includes two DC-DC converters 23 and 24 connected in parallel with the DC power source. One 23 of the DC-DC converters 23 supplies power to the infrared light emitting diode 20 and the oscillation circuit 22.

Abstract: A method of producing a speaker which is manufactured by bonding a plurality of speaker components, including steps of humidifying a joint portion which bonds at least two speaker components among the plurality of speaker components; and bonding the speaker components by humidifying the joint portion and thereafter painting a moisture-curable adhesive on the joint portion, to thereby reduce a time for bonding the speaker components by easily and quickly drying regardless of materials of the speaker components.

Abstract: An amplifier circuit for capacitive transducers, such as miniature electret or condenser microphones, wherein the amplifier circuit comprises bias control means adapted to improve settling of the amplifier circuit. Another aspect of the invention relates to a miniature condenser microphone and a monolithic integrated circuit comprising an amplifier circuit according to the present invention. The present invention provides amplifier circuits of improved performance by resolving traditionally conflicting requirements of maintaining a large input resistance of the amplifier circuit to optimize its noise performance and provide fast settling of the amplifier circuit.

Abstract: The invention provides an interfacing circuit for a removable microphone. In one embodiment, the interfacing circuit comprises a jack for receiving the removable microphone and an integrated circuit comprising a biasing circuit, a buffer amplifier, and an insertion detecting circuit. The jack comprises a first terminal receiving an output voltage of the removable microphone and a second terminal coupling the removable microphone to a ground voltage source. The integrated circuit is coupled to the first terminal of the jack via a first node. The biasing circuit, coupled between the first node and a second node, biases the removable microphone and passes only an alternative current (AC) portion of the output voltage of the removable microphone to the second node. The buffer amplifier, coupled to the second node, buffers the AC portion to generate a voltage signal.

Abstract: An audio processing system is provided. The audio processing system comprises a transducer, a gain stage, a capacitor network, and a preamplifier. The transducer transduces a sound signal to a voltage signal. The gain stage comprises an input coupled to the transducer and an output. The capacitor network, coupled between the output of the gain stage and the transducer, provides an equivalent capacitance. The preamplifier coupled to the transducer amplifies the voltage signal.

Abstract: A microphone includes a microphone capsule biased with a polarization voltage from a winding on a transformer. The polarization voltage is controlled by a regulation circuit that may have an analog regulation circuit and a digital regulation circuit. A controller adjusts the polarization voltage that varies the sensitivity of the microphone.

Abstract: A circuit module for a condenser microphone includes a first chip mounted on a mounting surface of a printed circuit board and including an impedance converter circuit for amplifying an electrical signal received from a capacitive sensor via a first conductive pattern on the mounting surface and for outputting an amplified electrical signal. A second chip is mounted on the mounting surface of the printed circuit board, and includes a filtering circuit for filtering the amplified electrical signal received from the first chip via a conductive wire unit and a second conductive pattern on the mounting surface. The first chip and the second chip are further coupled to a ground pattern on the mounting surface.

Abstract: A microphone assembly includes one or more transducers positioned in one or more housings. A processing circuit is coupled to the transducer for outputting an electrical signal such that the microphone in combination with the processing circuit very effectively cancels noise. The microphone assembly can be employed in a vehicle accessory.

Abstract: In a condenser microphone in which a microphone capsule and an audio output section are connected to each other via a microphone cord, strong electromagnetic waves generated by a cellular phone etc. are prevented from being transmitted by the microphone cord and intruding into the audio output section. In a condenser microphone in which a microphone capsule 10 and an audio output section 20, in which a circuit board 23 including an audio output circuit is housed in a shield case 210, are connected to each other via a microphone cord 30, of the circuit board 23, a terminal 231 connected to the microphone cord 30 is arranged on the outside of the shield case 210.

Abstract: In a condenser microphone where a microphone capsule and an output module section are connected to each other via a microphone cord, strong electromagnetic waves generated from a cellular phone or the like are positively prevented from entering the output module section through the microphone cord. The condenser microphone in which a microphone capsule 10 and an output module section 20 are connected to each other via a microphone cord 30 composed of a twin-core shield covered wire, the microphone capsule 10 including a condenser microphone unit 12 and an impedance converter 13, the output module section 20 storing, in a shield case 21, a circuit board 22 including a voice output circuit, wherein a shield covered wire 33 of the microphone cord 30 is connected to the shield case 21, and the shield covered wire 33 is also connected to a ground circuit of the circuit board 22 via a high-frequency choke coil 51.

Abstract: The invention is based on the idea of providing a detection device which is capable of distinguishing whether a microphone or audio signal processing arrangement connected thereto operates on an analog or digital basis. An analog or digital connection is selected in accordance with that determination procedure. Consequently there is provided a detection device which has a sensing device, a determining device and a selecting device. The sensing device senses an external signal fed to the detection device and forwards that signal to the determining device. The determining device determines whether the sensed external signal was transmitted by an analog or digital signal processing apparatus and transmits a corresponding determination signal to the selecting device. The selecting device then selects either an analog or a digital connection, in dependence on the determination signal.

Abstract: A microphone module includes a cabinet, a sensor, an integrated circuit chip, a first substrate, and a second substrate. The first substrate carries the integrated circuit chip and includes a first top surface, a first bottom surface, and a first shielding part with a fixed electric potential extending from the first top surface to the first bottom surface. The second substrate includes a second top surface contacting the first bottom surface, a second bottom surface, and a second shielding part with the fixed electric potential on the second bottom surface, wherein the second shielding part is arranged in such a way that no electromagnetic waves can pass between the first shielding part and the second shielding part.

Abstract: The present invention discloses a Micro-Electro-Mechanical Systems (MEMS) capacitive sensing circuit wherein two input nodes of a fully differential amplifier are separately connected to a MEMS capacitive sensing device and a matching capacitor, which both contain similar capacity value and connect to a bias node, and two resistors separately connect the MEMS capacitive sensing device and the matching capacitor to ground (zero voltage). Thus, the present invention could effectively eliminate the bias noise in the circuit without any discrete capacitor and capable for designer to integrate all circuit devices into an IC.

Abstract: A condenser microphone is provided having a transducer element. A diaphragm has an electrically conductive portion. A back-plate has an electrically conductive portion. A DC bias voltage element is operatively coupled to the diaphragm and the back-plate. A collapse detection element is adapted to determine a physical parameter value related to a separation between the diaphragm and the back-plate. A collapse control element is adapted to control the DC bias voltage element based on the determined physical parameter value.

Abstract: Microphones are used in acoustically insulated masks, headsets, phones and personal digital assistants. Frequently, the microphone provides an input to speech recognition software. The working environment is often humid and the speaker's mouth is in close proximity to the microphone. Frequently the signal suffers from clipping and distortion caused by the large signals and nonlinear response of the microphone circuitry. The claimed invention uses a resistor connected in parallel with the signal source to reduce its sensitivity and to produce a signal suitable for use with speech recognition software. The resistor can be varied for different speakers.

Abstract: The DC magnetization of a transformer core is prevented without increasing the size of an output transformer in a condenser microphone which is operated by a phantom power source, uses a vacuum tube as an impedance converter, and outputs a vacuum tube signal via the output transformer. The condenser microphone includes a condenser microphone capsule MC, a vacuum tube V01 used as an impedance converter, and an output transformer TRS having a primary winding F connected to the plate and screen grid of the vacuum tube V01 and a secondary winding S connected to the phantom power source via an output connector, wherein the primary winding F has a center tap CF and both ends of the secondary winding S are connected to the center tap CF via constant current diodes D04 and D05, respectively.

Abstract: An acoustic pressure type sensor is fabricated on a supporting substrate by depositing and etching a number of thin films on the supporting substrate and by machining the supporting substrate. The resulting structure contains a pressure sensitive, electrically conductive diaphragm positioned at a distance from an electrically conductive fixed electrode. In operation, the diaphragm deflects in response to an acoustic pressure and the corresponding change of electrical capacitance between the diaphragm and the fixed electrode is detected using an electrical circuit. Two or more such acoustic sensors are combined on the same supporting substrate with an interaural flexible mechanical connection, to form a directional sensor with a small surface area.

Abstract: A microphone and a method for producing a microphone with a sensitivity stipulated within narrow limits. The microphone each has a microphone capsule and an amplifier. A network of passive components, preferably resistors, is allocated to the amplifier. The sensitivity of the microphone is measured and the passive components are then disconnected to change the amplification of amplifier in the desired manner.

Abstract: A combination of a microphone and a sigma-delta A/D converter include at least one feedback loop, such as a DC feedback loop. The DC feedback loop provides the bias current for a junction FET of the microphone. In this way, the signal current from the FET can be injected directly into the input integrator of the sigma-delta A/D converter without the need of signal resistors in series with the FET.

Abstract: A semiconductor die with an integrated electronic circuit, configured so as to be mounted in a housing with a capacitive transducer e.g. a microphone. A first circuit is configured to receive an input signal from the transducer at an input node and to provide an output signal at a pad of the semiconductor die. The integrated electronic circuit comprises an active switch device with a control input, coupled to a pad of the semiconductor die, to operatively engage or disengage a second circuit interconnected with the first circuit so as to operate the integrated electronic circuit in a mode selected by the control input. That is, a programmable or controllable transducer. The second circuit is interconnected with the first circuit so as to be separate from the input node. Thereby less noise is induced, a more precise control of the circuit is obtainable and more advanced control options are possible.

Abstract: A microphone is described including a microphone housing having a microphone capsule disposed therein. The microphone is connected via a microphone cable to an audio system, and has an integrated amplifier that raises the signal output level. The integration of a preamplifier into the microphone advantageously reduces the microphone's susceptibility to interference. In contrast to conventional preamplifiers, the preamplifier does not, or not exclusively, operate as an impedance converter, but instead amplifies the output voltage. As a consequence, the signal-to-noise ratio is advantageously increased even in the presence of interference. The preamplifier can be provided with energy via a battery or accumulator mounted in the microphone, or advantageously from the audio system via additional conductors in the microphone cable.

Abstract: An apparatus and method for making a microphone that is not susceptible to RF noise and that can be fabricated to be very thin. The microphone includes a light transmitter configured to generate light, a waveguide having optically aligned transmit, vibrating and receive sections, and a receiver. Light from the transmitter is configured to be transmitted through the transmit section, vibrating section and the receive section of the waveguide, and to the receiver. The vibrating section of the waveguide is configured to vibrate in response to received acoustic energy, so that the light received by the receive section is modulated in proportion to the acoustic energy. In response, the receiver converts the modulated light to an electrical signal that is indicative of the received acoustic energy. Since the microphone of the present invention uses a thin waveguide to modulate the acoustic energy, it is not susceptible to RF noise, and it can be made to have a very thin profile.

Abstract: A silicon microphone includes a silicon microphone device, on which four acoustic transducers are integrated, an integrated circuit device and a package for housing the devices in an inner space defined therein, and the four acoustic transducers have different values of sensitivity and, accordingly, different values of dynamic range; the analog acoustic signals are supplied from the four acoustic transducers to the integrated circuit device, and are converted to digital acoustic signals; the digital acoustic signal output from the acoustic transducers with relatively high sensitivity are normalized with respect to the digital acoustic signal output from the acoustic transducer with lowest sensitivity, and the normalized digital acoustic signals are selectively formed into a composite acoustic signal depending upon the sound pressure of sound waves so that the dynamic range is expanded without sacrifice of high sensitivity in the low sound pressure range.

Abstract: An integrated circuit (102) configured to provide a microphone output signal, comprising: a preamplifier (108) coupled to receive an input signal, generated by a first microphone member that is movable relative to a second microphone member; and a voltage pump (104) to provide a bias voltage to either microphone member.

Abstract: The present invention prevents the occurrence of noise caused by an external electromagnetic wave. The present invention also prevents a high voltage from appearing in the microphone case, thus avoiding the possibility of an electric shock. A condenser microphone includes a conductive microphone case 10 containing an electronic circuit 20 for a condenser microphone unit and a 3-pin type output connector 30 attached to the microphone case 10 and to which a microphone cable 40 from an external apparatus including a polarization power source is connected. A first pin for grounding included in the output connector 30 is connected directly to the microphone case 10 and is also connected to a ground of the electronic circuit 20 via a high-frequency choke coil 31.

Abstract: A microphone bias circuit includes a first integrated circuit (IC) pin, a second IC pin, a first resistor, and a variable supply voltage buffer. The first resistor is operably coupled to the first IC pin and a return voltage. The second IC pin is operably coupled to receive analog signals from a microphone. The variable supply voltage buffer is operably coupled to produce a buffered supply voltage based on a variable impedance setting, wherein at least one off-chip component couples the second IC pin to the first IC pin and wherein the variable supply voltage buffer provides the buffered supply voltage to second IC pin as a microphone bias voltage.

Abstract: An apparatus having a microphone and a mute circuit (not shown in detail here) operable to be actuated by a rotating door assembly. The apparatus provides a mute circuit suitable to mute the audio microphone when the rotating door assembly is in a closed position and unmute the audio microphone when the rotating door assembly is not in the closed position. Additionally, the mute circuit is impervious to generating audible disturbances in the microphone signal when the rotating assembly door is rotated between open and closed positions. This advantageously allows for the microphone to essentially transition to off when the rotating door assembly is closed and transition to on when the rotating door assembly is open and do so without additional audio disturbance.

Abstract: An acoustic pressure type sensor fabricated on a supporting substrate is disclosed. The acoustic sensor is fabricated by depositing and etching a number of thin films on the supporting substrate and by machining the supporting substrate. The resulting structure contains a pressure sensitive, electrically conductive diaphragm positioned at a distance from an electrically conductive fixed electrode. In operation, the diaphragm deflects in response to an acoustic pressure and the corresponding change of electrical capacitance between the diaphragm and the fixed electrode is detected using an electrical circuit. Two or more such acoustic sensors are combined on the same supporting substrate with an interaural flexible mechanical connection, to form a directional sensor with a small surface area.

Abstract: A system for processing a sound input to a MEMS microphone in a voice communication device, such as a cellular telephone. The system includes the microphone and a processing microchip. The processing microchip includes a differential receiver that receives the signal output of the microphone on one input and a voltage that biases the microphone on the other input. The output of the differential receiver represents the audio signal from the microphone, while noise signals induced on connections between the microphone and microchip are received equally on the differential receiver inputs, thereby cancelling. Further, the processing microchip also includes a bias voltage generator circuit for supplying a bias voltage to the microphone. Noise that is coupled onto or is inherent in the bias voltage generator circuit or couples onto the signal path from the bias voltage generator to the microphone will traverse substantially symmetrical paths to the differential receiver.

Abstract: A system remotely controls a microphone through a remote control unit. The remote control unit includes a frequency modulator that modulates a control signal. A cable conductor that is used to provide phantom power also conveys a frequency-modulated control signal. The frequency-modulated control signal and audio signals may be separated.

Abstract: An electret-condenser microphone according to the present invention includes a vibrating diaphragm and a back electrode which compose a condenser; a cylindrical case which houses the vibrating diaphragm and the back electrode; a circuit board which is housed in an opening of the cylindrical case, is fixed to the opening by crimping a crimp edge formed by bending an opening end of the cylindrical case inward, and covers the opening; and a substrate fastened to an outer surface of the circuit board. A circular pattern and annular pattern are formed on the outer surface of the circuit board and a circular pattern and annular pattern are formed on that surface of the substrate which is farther from the circuit board. The circular pattern and annular pattern are connected with the circular pattern and annular pattern via thru-holes in the substrate, and that surface of the substrate on which and are formed serves as a reflow-soldering surface.

Abstract: Microphones are used in acoustically insulated masks to prevent the speaker's voice from being overheard by others. Frequently, the microphone provides an input to speech recognition software. The environment inside the mask is often humid and the speaker's mouth is in close proximity to the microphone. The shape of the mask's shell and the restricted volume within the shell introduce distortion and the signal suffers further from clipping and distortion caused by the large signals and nonlinear response of the microphone circuitry. The use of an electret microphone is particularly troublesome due to its high sensitivity. This invention uses a resistor connected in parallel with the microphone to reduce the sensitivity of an electret microphone used in these conditions and produces a signal suitable for use with speech recognition software. The resistor can be varied for different speakers.

Abstract: A low power high dynamic range microphone amplification system is disclosed. The system includes a current sensing amplifier for receiving an input current signal representative of auditory information and for providing an amplifier output signal. The current sensing amplifier includes a DC bias network that includes a cascode filter.

Abstract: A circuit includes a differential amplifier having a first input for coupling to a first terminal of a microphone and a second input for coupling to a first terminal of a component having an impedance value that is substantially equal to an impedance value of the microphone, where a second terminal of the microphone and a second terminal of the component are coupled to circuit ground. The circuit further includes a first resistance having a first node coupled to a source of microphone bias voltage and a second node coupled to the first terminal of the microphone; and a second resistance having a first node coupled to the source of microphone bias voltage and a second node coupled to the first terminal of the component. Operation of the differential amplifier results in attenuating or suppressing common mode noise and interference present in the microphone bias voltage and in the common potential.

Abstract: In a rolling process, the level of rolling performed by a rolling mill for one operation is set to 1 ?m to 20 ?m. A magnesium substrate is rolled by rollers while being heated by a thermostatic chamber. As a result, there is manufactured a high-quality magnesium sheet which is less susceptible to influence of oxidation, which realizes a high internal loss, prevention of a drop in sensitivity, and low distortion, and which has a thickness of 30 ?m to 100 ?m. Further, as a result of the magnesium sheet being formed into a semi-dome shape or a dome shape, the sheet can be inexpensively manufactured as a speaker for high-tone playback. In particular, in the case of a magnesium diaphragm into which a dome section and an edge section are integrally formed, high-quality sound can be played back in a high frequency range without involvement of a drop in sensitivity.

Abstract: A loudspeaker and method of assembly according to this invention provides for precise alignment between the frame and motor structure before they are connected to one another, and employs a fixture to form the moving assembly of the speaker, i.e. the voice coil, upper and lower suspensions and diaphragm, outside of the frame so that concentric tolerance stack-up is minimized. The moving assembly, once formed, is mounted as a unit to the frame and motor structure to facilitate assembly and repair of the speaker.

Abstract: A microphone circuit includes an amplifier for amplifying an electric signal output from an electroacoustic transducing module, an external power supply circuit capable of supplying power for driving at least the amplifier from the outside, a light source that is turned on when an external power is supplied through the external power supply circuit, and a photo relay having contacts that are turned on and off in response to blinking of the light source. The contacts of the photo relay are connected so as to output an output signal of the amplifier as a microphone output when the light source is turned on and output an output signal of the electroacoustic transducing module as the microphone output when the light source is turned off.

Abstract: A number of improved structures and methods to a condenser microphone device are provided so that the condenser microphone device can be used in a skin-contact manner satisfactorily. According to the proposed methods, the sensitivity of the condenser microphone device is lowered appropriately by reducing the aperture of the through hole on the enclosure of the condenser microphone device's sensing member, or by reducing the amount of electrical charge carried by the thin film inside the sensing member. According to the proposed structures, the sensing member is wrapped inside a plastic jacket or film, covering up the through hole on the sensing member's enclosure, or providing another through hole of very small aperture. The plastic jacket could also form a buffer space between the jacket and the sensing member.

Abstract: The present invention provides a low noise phantom powered capacitor microphone and a method of using a vacuum tube as an impedance converter of the microphone capsule in the capacitor microphone with no exclusive power supply. In the phantom powered capacitor microphone of which a vacuum tube V01 is used as the impedance converter, a part of the voltage supplied from the phantom power supply is converted to a predetermined voltage by one or more switched capacitor voltage converters, for example, by three switched capacitor voltage converters IC01, IC02 and IC03 seriously connected as three stages to obtain the heater voltage of the vacuum tube V01.

Abstract: An electroacoustic capsule or electroacoustic transducer for an electroacoustic device has electrostrictive or magnetostrictive elements connected to a controllable power supply. Dimensional changes of the electrostrictive or magnetostrictive elements cause changes of the inner geometry of the electroacoustic capsule or electroacoustic transducer. This allows the adjustment of the capsule or transducer to the electroacoustic device in which it is mounted so that individual and dynamic adjustments are possible.

Abstract: The invention provides a method for reducing phase variation of a signal generated by an electret condenser microphone. An error of a capacitance of the electret condenser microphone is reduced. An impedance of the electret condenser microphone is increased. A shunt resistance is added to the electret condenser microphone. A ?3 dB cut-off frequency of the electret condenser microphone is lowered.

Abstract: Electro-dynamic loudspeakers typically include a diaphragm having a conductor applied to one of its surfaces. The diaphragm is secured to a frame. The conductor is connected to a power supply for providing electrical current through linear traces of the conductor that interact with magnetic fields generated by magnets that are mounted to the frame. The diaphragm is driven by a motive force created when current passes through the conductor within the magnetic field. The electrical current is varied to create an acoustical output from the electro-dynamic loudspeaker. Different methods of tensioning the diaphragm are provided for simplifying the manufacturing process and for assuring proper diaphragm tension.

Abstract: In a condenser microphone which selectively uses a phantom power supply and a built-in battery power supply, and which switches load resistance elements of an impedance converter corresponding to a selected power supply, a noise due to the high frequencies is prevented from occurring even if a cellular phone or the like is used in the vicinity. The condenser microphone includes: a condenser type electro-acoustic transducer element; an impedance converter that converts an output impedance of the electro-acoustic transducer element; load resistance elements of the impedance converter; a phantom power supply and a built-in battery power supply for operating the impedance converter; a switch that switches the values of the load resistance between at the time of using the phantom power supply and at the time of using the built-in battery power supply, wherein the switch is an optical switch that turns on/off optical coupling.

Abstract: A surface mounted device (SMD) type biased condenser microphone includes two terminals for a surface mounting process. The SMD type biased condenser microphone includes a grounding terminal for connecting with an external circuit, a diaphragm/backplate set, one end of which is connected to the grounding terminal, for varying a capacity according to an intensity of sound pressure and converting sound into an electric signal, a DC-DC converter for providing a bias voltage so as to form an electrostatic field at one side of the diaphragm/backplate set, a buffer IC for amplifying the electric signal from the diaphragm/backplate set, and a decoupling capacitor for preventing the bias voltage output from the DC-DC converter from being directly applied to the buffer IC and transferring the electric signal from the diaphragm/backplate set to the buffer IC.