Abstract: A broadband microfabricated ultrasonic transducer which includes a plurality of resonant membranes of different sizes and/or shapes supported above a conductive substrate.

Abstract: In a capacitor microphone system for directional applications, an array of backplates of microphone cells are formed on a printed circuit (PC) board. A continuous strip of diaphragm is employed to cover each backplate. The diaphragm is stretched to create a uniform tension along its length, contributing to the objective of achieving a uniform gain by each microphone cell. In addition, the diaphragm is separated from the backplates by a relatively large distance such that the percentage deviation from such a distance from cell to cell is relatively small, again contributing to the objective of gain uniformity.

Abstract: An integrated capacitive transducer (1) which includes a membrane having a movable part (4) with an electrode, a fixed plate (6) with a counter-electrode (8), and an electrode and counter-electrode support structure (10). The fixed plate (6) also has an electret (30) which is disposed facing the movable part (4), is separated from the membrane by an open space (16), and has a first electrically conductive layer (32) embedded in an insulating material (34, 36). The invention has particular applications in hearing aids.

Abstract: An electrostatic ultrasonic transducer formed on a semiconductor substrate by micro-machining wherein the transducer includes a silicon nitride membrane supported above the surface of the substrate by insulating supports; and the substrate and membrane define the electrodes of the transducer.

Abstract: A diaphragm for capacitance type loudspeaker is disclosed. The diaphragm uses a conductive high polymer layer as a conductor formed on a high molecular film of PET or the like by treating the high molecular film in a water solvent solution containing a conductive high molecular monomer, a chemical oxidizer and a dopant. The conductive high molecular monomer is selected from the group consisting of pyrrole, aniline, thiophene and derivatives thereof.

Abstract: A common-source type buffer amplifier circuit has a microphone capsule, a diode and an FET. An output end of the buffer amplifier circuit, or a drain of the FET is connected to an input end of the current mirror circuit. An output end of the current mirror circuit is connected to one end of a load resistor of which the other end is grounded. A voltage across the load resistor corresponds to an output of the amplifier and is supplied to the speaker amplifier.

Abstract: An amplifier circuit for an electret condenser microphone includes an operational amplifier, an operational amplifier, a bias circuit, and a power supply circuit. The operational amplifier has an inverting input terminal for receiving an output of a two-wire lead electret condenser microphone and a noninverting input terminal for receiving a bias voltage. The bias circuit divides a power supply voltage to generate the bias voltage. The power supply circuit applies the power supply voltage to the electret condenser microphone through the bias circuit and a first resistor.

Abstract: This invention relates to sound systems and more particularly to such systems that present sound to a listener in a "full wrap-around" manner.

Abstract: A solid state miniature condenser and condenser microphone of good sensitivity is disclosed. The microphone comprises a fixed perforated backplate that constitutes a fixed electrode in a parallel plate condenser, a diaphragm sensitive to incident sound pressure waves that constitutes a moveable plate in the parallel plate condenser, keepers to position the diaphragm in relationship to the backplate without applying appreciable tension to the diaphragm, and FET circuitry which provides an output proportional to the change in capacitance of the condenser when the diaphragm moves in relationship to the backplate.

Abstract: A post assembly process for enabling a manufacturer of acoustical communications apparatus, such as telephones and the like, to conveniently trim a sensitivity characteristic of an electret microphone therein, after assembly of the apparatus, whereby a uniform performance standard may be adhered to. When the acoustical sensitivity characteristic of the electret transducer is measured to be greater than a predetermined value, the transducer is exposed to X-ray radiation until the measured sensitivity characteristic has been reduced to the predetermined value.

Abstract: An improved electrolytic loudspeaker assembly (10) designed to reproduce a broad band of audio signals and that consists of a thin, non-magnetic capacitive transducer (12) and a transducer driver unit (60). The transducer (12) consists of a compound diaphragm (14) further consisting of a vibratory center section (16) having attached to each of its surfaces a respective front section (26) and back section (32). All three sections of the compound diaphragm are held captive by a frame assembly (40). The transducer (12) is driven and controlled by the transducer driver unit (60). The unit couples the audio signal to the transducer's front and back sections (26) (32) and supplies an unregulated, d-c bias voltage to the transducer's center section (16). The unit (60) maintains the proper ratio between the bias voltage and audio signal to achieve optimum performance.

Abstract: An electret transducer array and fabrication technique are disclosed. The array comprises a foil having a layer of insulating material and a layer of metal in contact therewith. The layer of metal comprises one or more discrete areas of metal which define the active areas of one or more transducers in the array. Electrical leads are coupled to the discrete areas of metal. By means of these leads, electrical signals produced by each transducer in response to incident acoustic signals may be accessed. The areas of metal may be formed by selectively removing metal from the foil, or by selective metal deposition. The layer of insulating material is electrostatically charged. The electret transducer array further comprises a porous backplate of sintered metal. The backplate further comprises a rough surface in contact with the layer of insulating material. The backplate serves as a common electrode for transducers of the array.

Abstract: An acoustic echo canceler and a side-tone echo canceler provided in a hands-free telephone suppress an acoustic echo and a side-tone echo respectively with few error by providing automatic gain controllers and/or limiters in the hands-free telephone so that the acoustic echo canceler and the side-tone echo canceler operate in linear, and a directional characteristic of a microphone used in the hands-free telephone for reducing the acoustic echo is controlled by a microphone direction controller so that the microphone operates as an omnidirectional microphone when a level of a received signal of the hands-free telephone is less than a designated level and as a bidirectional microphone when the level exceeds the designated level, further gains of an output of the microphone increases in a low frequency range.

Abstract: A microphone apparatus including a vacuum-tube amplifier amplifying an electric signal converted from an acoustic signal includes a thermo-ionic cooling element having two surfaces, in which a first surface is in contact with the vacuum-tube amplifier for absorbing the heat generated from the vacuum-tube amplifier and the absorbed heat is radiated to the exterior from the second surface.

Abstract: A microphone comprises a plurality of oppositely oriented electroacoustic transducer pairs arranged in a body or a resonator cavity and electrically algebraically summed, whereby ambient acoustic shock impulses and vibration induce opposite electrical phase output, while an audio signal entering an acoustic channel to the transducer cavity produces a damped, in-phase, summed output, greatly enhancing the signal to noise ratio and producing a high output level that is substantially non-microphonic.

Abstract: Hearing aid for persons with an impaired hearing faculty, including a directional microphone whose pick-up characteristic can be altered, the pick-up characteristic being automatically controlled as a function of the input or output signal in such a way that all possible microphone characteristics may be set, and this is realized in that the directional microphone (10) is an electret microphone and that the changes in the pick-up characteristic take place electrically and continuously.

Abstract: An acoustical transducer unit mountable in a speaker enclosure with a speaker opening adapted to face a user's ear, and a method for manufacturing the transducer. The transducer has a pair of opposing plates spaced apart a predetermined distance and a diaphragm physically connected and positioned between the plates, though electrically separated from the plates. The plates are adapted to be connected to an audio signal source, while the diaphragm receives a bias voltage. The transducer is mounted in the enclosure facing outward toward the speaker opening. The diaphragm is formed of a flexible substrate material such as MYLAR.TM.. A substantially infrared transparent material is deposited onto each side of the substrate in a thin layer to arrive at a transducer which is at a much higher level of performance than those of the prior art. The deposited material is infrared transparent so as to permit the deposition process to proceed without substantial damage or distortion to the diaphragm.

Abstract: An electret transducer including a pair of spaced electrodes, one electrode being connected to a preamplifier input, an insulator on the outer surface of the electrode connected to the preamplifier input, and a conductive layer on the other side of the insulator, whereby the conductive layer can be used to shield the electrode to reduce stray capacitance between it and other components of the transducer by connecting the conductive shield to the output of the preamplifier circuit for the transducer. Also disclosd is the use of a silicon backplate with an integrated circuit formed therein, an insulator layer thereon, a conductive layer thereon, and an electret layer thereon, the conductive layer being grounded during poling of the electret to protect the integrated circuit from damage.

Abstract: A method and apparatus for controlling the sound pressure levels of a substantially capacitive speaker. The controlling element is substantially capacitive and may be either fixed or variable.

Abstract: An electronic telephone terminal having a transmitter and a receiver, both having an approximately linear acoustic-to-electric transduction characteristics, and having a surrounding noise suppression function, and including a variable attenuator for controlling a gain of a transmission system; a noise detection device for detecting surrounding noise; and a control device for controlling the variable attenuator in such a manner that when a sound pressure level input to the transmitter exceeds a predetermined threshold value, the gain is fixedly set to a constant value, and when the input sound pressure level is equal to or below the predetermined threshold level, the gain is controlled in response to a change in the surrounding noise level detected by the noise detection device.

Abstract: An electrostatic transducer with a diaphragm supported by means of a stretching ring, and a back plate which is formed by a thin metal plate supported on a carrier member and mounted spaced apart from the diaphragm. A plurality of support members are attached to the carrier member and distributed over the area of the carrier member. The base plate is glued to the free ends of the support members. In this transducer, the use of very thin metal plate as back plates is possible.

Abstract: A microphone comprising a double membrane condenser unit and an amplifier circuit is connected to a power supply. Signals from the two membranes of the unit are fed to each one amplifier and to each one impedance transformer and are delivered through a signal wire to a power supply unit having phantom power supply. In the power supply unit, the signals are added or subtracted in order to give a continuously variable directional characteristic of a round or eight characteristic and are added or subtracted in different proportions by means of a potentiometer in order to give different degrees of a cardioid characteristic. The microphone can also be used as a stereo microphone by assigning the two signals to the right and the left channel, respectively. For balanced signals an inverting buffer is used and a second impedance transformer.

Abstract: A voice switched gain system is disclosed for loudspeaking telephone and hearing aid applications involving electret microphones. A voice switched gain circuit comprises an audio pre-conditioning circuit for providing a conditioned audio input referenced to an unconditioned audio input to a compandor circuit. A linear gain level reference generator circuit generates a level for comparison with the audio input level. A decision circuit then controls the compandor operation based on the result of the comparison. The decision circuit either maintains the audio output of the compandor in a compressed state or expands the audio input signal to a higher level expanded state for transmission. Two such circuits are provided in a loudspeaking telephone system, one circuit for maintaining a preemptive near end control through appropriate timing of the dual decision process. Far end control is provided by the other voice switched gain circuit.

Abstract: An electroacoustic transducer includes a base plate made of insulating material, a stationary electrode formed on one side of the base plate and made of electrically conductive material, an annular support formed on the same side of the base plate and surrounding the stationary electrode, the annular support being made of the same electrically conductive material as the stationary electrode, and an electrically conductive diaphragm applied on the annular support.

Abstract: A throat microphone has an outer resonant diaphragm which is adapted to be secured against the throat of a wearer and which cooperates with a housing to form an outer chamber. An electret microphone element disposed inside the outer chamber includes an electret diaphragm acoustically coupled to the outer diaphragm and an electret housing forming an inner chamber with the electret diaphragm. The electret diaphragm is perforated to provide pressure relief between the two chambers to give the electret microphone element a rising response characteristic, which is enhanced by a differentiating network in the input circuit of a local preamplifier. The outer diaphragm is so formed as to have a principal resonance at about 3 kilohertz to provide a further emphasis to voice frequencies at or near that resonance.

Abstract: A transducer rendered operative by a battery voltage source is mounted on and closely spaced from a sonic radiating surface by a sonic coupling body to which a housing is secured in enclosing relation to both the transducer and the battery source. Openings in the housing expose a volume control knob and an output signal jack through which a signal cable connects the transducer to a remotely located amplifier.

Abstract: A ceramic microphone is described which comprises a diaphragm for receiving sound waves, a thin ceramic plate attached to the diaphragm for transducing the sound waves to electric signals, and a plurality of electrodes on each of the opposite sides of the ceramic plate, the plurality of electrodes being polarized so that each of a pair of the electrodes faced across the ceramic plate forms a capacitor and the opposite-polarity electrodes of each of the capacitors are serially connected each other.

Abstract: An electroacoustic transducer system comprises a microphone working into a low-frequency amplifier for the energization of an a-c load such as, for example, a loudspeaker or a volume indicator at a control panel. Biasing voltage for the microphone and operating current for the amplifier are derived from a d-c source, via a phantom circuit including the output leads of the amplifier and through a coupler in cascade with a chopper; the latter includes a transistor conducting intermittently under the control of an adjustable pulse generator whose pulse width is varied by negative feedback from the integrated chopper output. An output transformer with a primary in series with the transistor has several secondaries each connected across a storage capacitor through a diode for the generation of a relatively high biasing voltage for the microphone, a relatively low driving voltage for the amplifier and, possibly, a further voltage used to vary the directional pattern of the microphone.

Abstract: An electret microphone gain regulation circuit employing an active load for use in high quality telephone instruments or handsets where two terminal electret microphones of the current source type are employed. The circuitry provides a heavier load on short loops and a lighter load on long loops to regulate the signal level at its output.

Abstract: A battery-powered miniature acoustical transducer system for a hearing aid, including a microphone and an amplifier, has a combination filter and voltage regulator incorporated in its power supply circuit; the filter/regulator includes a field-effect transistor having its drain and source electrodes interposed in series between one battery terminal and a first power terminal of the amplifier, a resistor connecting the source and gate electrodes of the FET, a transistor having its emitter and collector interposed in series between the other power terminal of the amplifier and the gate electrode of the FET, and a junction diode connected from the FET source electrode to the transistor base, the diode junction and the base-emitter junction of the transistor both having highly non-linear voltage/current characteristics.

Abstract: A microphone output transmission circuit for a capactive microphone such as an electret microphone employs a differential amplifier to provide a transformerless balanced connection to a microphone transmission line, either at the transmission end or at the reception end thereof. Power is applied in a phantom connection by superimposing a DC voltage on two balanced signal conductors of the transmission line, and using the shield thereof as a ground return line. A pair of microphones with oppositely-directed sound-gathering planes can be connected to respective inputs of a differential amplifier at the transmission end, so that the two microphones together have a bidirectional characteristic.