Showing papers on "Microphone published in 1980"

Wireless transmitting and receiving systems including ear microphones

Abstract: A wireless transmitting and receiving system includes an ear microphone of the vibration pick-up type for picking up bone-conducted voice signals through an external auditory ear canal wall of a wearer. A portable case is disposed adjacent the wearer's ear and a wireless device is attached adjacent the wearer but spaced from the portable case. A transmitter of a transmitting circuit for transmitting the output signals of the ear microphone is housed in the portable case. A receiver of a receiving circuit is housed in the wireless device and receives signals from outside the system. The transmitting and receiving circuits provide a wireless connection between the portable case and the wireless device permitting two-way communication through one ear of the wearer.

Electronic pick-up device for transducing electrical energy and sound energy of the heart

Abstract: A stethoscope transducer applicable as a conventional audio transducer and as a phonocardiogram transducer has a body which on one side mounts an electrode carrying chest bell and which on an opposite side mounts a conventional chest bell. A microphone and a rotor assembly are mounted in a cavity in the body. The microphone and earpiece connections on the body communicate through passages in the rotor assembly with the electrode carrying chest bell when the rotor assembly is in a first position and with the conventional chest bell when the rotor assembly is rotated to a second position. These are three electrodes, two being pickup electrodes which each occupy one quadrant of the chest bell rim in diametrically opposite positions. The third electrode is on the rim intermediate the pickup electrodes. The rim is of a non-wettable material providing a hydrophobic surface.

A comparison of contact microphone and electroglottograph for the measurement of vocal fundamental frequency.

Abstract: Signals from a throat contact microphone or an electroglottograph often are more suited for fundamental frequency measurements with simple analog circuits than the radiated speech signal. This report compares a contact (accelerometer) microphone placed on the neck below the cricoid cartilage and an electroglottograph for measurement of fundamental frequency in connected speech. The advantages and drawbacks of the two methods are discussed.

Method and apparatus for cancelling vibration

Abstract: Improved method and apparatus for the nulling of a primary vibration by the "active" method, based on the "virtual earth" system in which the output of a loudspeaker (3') is continually controlled by a feedback loop (1', 2' 3') to maintain a null at a microphone (1') disposed adjacent to the loudspeaker. In accordance with the invention the loop (1', 2', 3') is used as a generator for the correct waveform of the secondary vibration required to null the primary vibration, the amplitude at which the secondary vibration is projected into the primary vibration being increased to move the null point to the far field of the loudspeaker (3').

Variable-directivity microphone device

Abstract: A variable-directivity microphone device comprises a microphone unit having a plurality of microphones, a circuit which resultingly adds the low-frequency range components of the output signal of one of the microphones of the microphone unit and mixes with the output signal of the other microphone so that only the high-frequency range components cancel each other, and an equalizer which corrects the characteristic of the mixed signal. The above effective mixing is performed under varying mixing states.

Ultrasonic fluid leak detector

Abstract: A device for detecting ultrasonic noise, particularly such noise as generated by fluid leaks, includes a directional ultrasonic microphone, amplifiers and ultrasonic filters, an envelope detector, an audio preamplifier and filter, a level control, a meter, an audio power amplifier and speaker, and a phase shift feedback network connected from the output of the power amplifier to an input thereof. A switch is operable in a first setting to connect the power amplifier to the level control to convey the audio frequency amplitude envelope of the detected ultrasonic noise through the speaker or in a second setting to connect the power amplifier to the feedback network. A level detector is operatively connected to the level control and provides a control signal which is conducted to the feedback network. When the control signal exceeds a selected level, the feedback loop circuit is completed, whereby the power amplifier oscillates audibly through the speaker and gives audible indication of an ultrasonic noise. The components are enclosed in a pistol shaped housing for substantially single handed aiming and operation.

Microphones with rigidly supported piezopolymer membranes

Abstract: Piezoelectric microphones are described which utilize a rigidly supported, curved polyvinylidene fluoride membrane. The microphones can be designed with a resonance frequency of about 5 kHz and a sensitivity of −55 to −60 dBV per N/m2. The harmonic distortion is typically below 1% for sound‐pressure levels up to 100 dB. Advantages of these microphone structures are the well‐defined geometry of the membrane, good mechanical and thermal stability, and the possibility of varying the membrane tension and introducing damping by the membrane support.

Method of and apparatus for audiometrically determining the acoustic impedance of a human ear

Abstract: In order to determine the acoustic impedance of a human ear at various static pressures, a probe tightly fitted to the pinna of the ear transmits a short acoustic pulse with a wide frequency spectrum (such as white noise) from an electroacoustic transducer to the ear canal and receives back an acoustic response signal which a microphone converts into an electrical wave. The latter is digitized and transformed into terms of a Fourier series fed to a processor which, on the basis of similar terms stored in a memory and previously obtained with the same probe fitted to two different cylindrical calibrating cavities, derives therefrom the acoustic ear impedance at a particular air pressure. The processor also triggers an electric pulse generator, working into the electroacoustic transducer, and may progressively adjust a generator of static air pressure connected to the probe.

Mounting system for a mobile microphone

Abstract: A mobile microphone mounting system is disclosed for a mobile microphone having an encasement surrounding a microphone element. A rear wall of the encasement has a pocket with a thin wall at a base thereof. A ring-shaped magnet is positioned within the pocket with a flat major surface alongside the thin wall. A mounting member is mounted through a central aperture of the magnet to provide alternative mounting for the microphone. The magnet is positioned between a metal plate and the thin wall. A lip surrounding the pocket retains the plate and magnet therein. The microphone may be conveniently attached by magnetic attraction to any nearby surface or preferably to a cup-shaped metal mounting plate. A compatible clip assembly is also provided for alternative mounting.

Local external communication device for enclosed helmet and mask assembly

Abstract: A local external communication system for use with an enclosed helmet and mask assembly covering the head, ears, nose and mouth of the wearer and provided with earphones and a microphone and a plug for connection with a radio or intercom system, in which a housing adapted to be carried on a wearer's body houses a battery, a speaker and a microphone and carries a receptacle for receiving the communications plug of the mask and helmet assembly. The device includes a unity gain amplifier system having a peak limiting circuit associated with the microphone to limit amplification of external sounds to a safe level. A switch permits the wearer selectively to turn the device off, to listen only, or to both speak and listen through the device.

Hearing aid suitable for use under noisy circumstance

Abstract: A hearing aid in which input signals picked up through a microphone are divided to those of two or more frequency bands by means of a frequency division means, signal outputs of frequency band(s) in which noise signals are included are saturated or reduced by a compensating means such as compression or saturation amplifier, and mixed with signals of other signal of frequency band(s) which are not compensated, whereby ambient noises can be removed from voice sounds.

Relaxation time measurements in frequency and time-domain photoacoustic spectroscopy of condensed phases

Abstract: The use of the photoacoustic spectroscopy (PAS) technique to measure nonradiative lifetimes in either the frequency or time-domain mode is discussed. Expressions are presented for the dependence of the cell pressure upon the lifetime, and the modifications introduced by the microphone transfer function are discussed. It is shown that in both measurement modes thermally and optically thick specimens are preferred. Other sample types have contributions to the measured phase or time delay arising from the optical absorption depth and sample cell parameters. The model presented suggests that the PAS technique is suitable for the measurement of lifetimes in the range between 10−5 and 10−1 s, with the limits arising from the microphone transfer function, the finite sound velocity, and thermal transport velocity in the transducer gas.

Microphone mounting device

Abstract: A microphone mounting device has a shaft emulative of a microphone handle and a structure, for holding the microphone, attached to the shaft. In a preferred embodiment of the invention, the structure includes a ring having a central axis that is attached to the shaft in such a way that the central axis is generally parallel to the longitudinal axis of the shaft. In this embodiment there are disposed around the ring a plurality of elastic loops that releasably hold the microphone in place.

Combined pick and tuner

Abstract: A combined pick and stringed instrument tuning device includes a relatively flat, substantially rectangularly shaped housing having a pick attached thereto and is small enough to be easily held in one's hand. A momentary contact push-button switch mounted on top of the housing controls an electronic tuning circuit by selecting one of several predetermined frequencies from a frequency generator. In one embodiment, the tuning circuit is mounted in the housing so that the tuning device is totally self-contained. Alternatively, the tuning circuit is remotely located and is controlled by a cable connected to the housing or by radio signals. The frequency selected is displayed on the housing and the frequency generator drives a strobe light located near the pick. In another embodiment, a microphone mounted on the housing converts sounds from the string being tuned to a signal which is compared to the preselected frequency. One light on the housing indicates when the string frequency is too high and another indicates when it is too low.

Improved phonocardiogram system based on acoustic impedance matching.

Abstract: We considered that phonocardiographic recording could be improved 1) by minimizing the acoustic impedance mismatch between the precordial tissue and transducer, 2) by optimizing the configuration of the impedance-matching medium and transducer design, and 3) by storing signals in digital form through analog-to-digital conversion of analog recordings made at the bedside. The use of an aqueous coupling medium to improve energy transmission increased signal voltage approximately 100-fold over presently used commercial devices. Further match to the crystal was achieved by a concentrating horn configuration for the aqueous medium. Measured frequency response of the device in the range 1 Hz to 1 kHz was better than two other commercially tested microphones. Inspection of comparative phonocardiograms showed more information from the new device than from the two other commercial devices. Unfiltered digitized signals, using our microphone in normal subjects, demonstrated good beat-to-beat repeatability, but analog filtering to obtain the conventional phonocardiogram showed significant loss of information. The new instrument appears to be superior to those commercial devices tested in recording heart sounds.

Bi-directional underwater communication system

Abstract: A bi-directional underwater communication system provides a submerged operator with the capability to communicate with a surface site. A face-mask-mounted microphone and an earphone are connected to a submerged, watertight radio. The radio antenna cable is carried by a buoy to the surface of the body of water in which the operator is submerged.

Securing of lead wires to electro-acoustic transducers

Abstract: An electro-acoustic transducer of the dynamic type, particularly a small loudspeaker or microphone, such as a loudspeaker for use in headphones, comprises a magnetic circuit including an air gap, a diaphragm having a voice coil disposed in the air gap, and lead wires for the voice coil, the lead wires extending substantially tangentially from the voice coil and being bonded to the diaphragm by two different kinds of adhesive, a relatively hard adhesive being used near the voice coil and a relatively soft adhesive being used near the periphery of the diaphragm.

Methods and apparatus for alleviating sound-coupled feedback in conference room sound systems

Abstract: A method and apparatus for alleviating sound-coupled feedback in a conference room having a conference table for the seating of human participants, the room sound system including one or more loudspeakers for outputting amplified sound from a given source in sufficient volume for all to hear plus one or more microphones for picking up the voice of any given participant. By locating the loudspeaker(s) below the board-like table top, preferably at floor level attached to the table foot structure, and by locating the microphone(s) above the table top, preferably in the central region, sound waves from the loudspeaker(s) are directed with high efficiency coupling to the participants' ears, but are constrained by the table top to "feedback" to the microphone(s) only with low efficiency coupling. "Rain barrel" effects are reduced. The invention finds advantageous use in purely local conference room sound amplification systems and in teleconferencing systems.

The use of a miniature microphone in the ear canal for the verification of hearing aid performance.

Abstract: An individual head, auricle, and ear canal can alter signals from a hearing aid other sources of acoustic stimulation compared to artificial couplers. The most realistic method for quantifying or verifying certain parameters of acoustic simulation delivered to the ear by a hearing aid is to measure the sound pressure level of a signal in the ear canal of an individual while wearing an aid. Probe microphone measurements have been conducted and reported for the past 33 years. Until now, such microphone measurements have used a hollow tube inserted into the ear canal which leads to a transducer outside the canal. This paper describes our preliminary clinical application of a new wide range, flat response, miniature electret microphone, measuring 4 x 5 x 2 mm for measurement of insertion gain in a patient's ear canal. We believe the information from these recordings can be useful in developing objective clinical procedures for the selection and monitoring of wearable amplification for hearing-impaired patients.

Impedance measurement source and microphone proximity effects

Abstract: The input impedance Zin as normally defined is the air column pressure response to a unit plane‐wave flow excitation. The experimental measurement of Zin for an arbitrary air column is affected by the nearfield interactions between an excitory source (capillary, annulus, membrane, etc.) and microphone. In addition to the plane‐wave component, the source produces a local disturbance (due to the evanescent modes) at the microphone. The net microphone pressure pm can be written in terms of the source strength us, the wave impedance R0 and radius a of the air column entryway, and wavenumber k: pm = usR0[(Zin/ R0)+jkaE]. The evanescent mode factor E is real and independent of frequency for ka<1. Its value depends on the source and microphone geometry. Measured values agree with detailed calculation. Placement of one transducer along the center axis of the air column, with the other at R = 0.6a from the center eliminates all azimuthal mode coupling (Jm Bessel functions, m≳0), and minimizes the coupling to the l...

Audio data transmission device with coupling device

Abstract: An audio data transmission device for transmitting binary coded audio tones over a telephone system. The audio data transmission device is adapted to be utilized with a hand-held, data collection terminal provided with a speaker emitting binary coded audio tones. The transmission device consists of a muff for receiving the microphone portion of a conventional telephone handpiece and a solid transmission element. The transmission element is adapted to be mechanically connected to the housing for the terminal for channeling the data tones to the telephone handset without dampening. The transmission element is defined to be mechanically tuned to the characteristics of the telephone microphone to minimize the generation of second harmonics of the desired audio tones.

Automatic transmission or recording or transmission and reception control system

Abstract: A system to automatically control the changeover of recording and recording stop, or transmission and transmission stop, and being employed in the recording or transmitting device provided with a vibration pick-up type microphone for picking up bone-conducted voice sounds. The automatic changeover of recording and recording stop or transmission and transmission stop is attained by control signals corresponding to impact vibrations except voice signals uttered by a microphone wearer himself, transmitted through his bones and picked up by the microphone or another controlling microphone.

Radio controlled model vehicle - has electric drive and remote control system with loudspeaker on chassis for relaying recorded or direct sound transmitted from panel

Abstract: The radio controlled model vehicle is electrically driven and operated by a remote control transmitter of the standard type apart from a microphone which is mounted on the control box itself. This microphone is used to transmit modulated sound to the vehicle, where it is demodulated and emitted by a loudspeaker (26) mounted on the vehicle chassis (20). The chassis (20), also holds the drive motor (22) the battery clamp (21), the servo mechanism (24), the receiving antenna (25) and the receiver (23). A tape recorder can also be connected to the transmitter, allowing any desired sound to be emitted from the vehicle e.g. music, speech, instructions etc. An inertia switch (27) can also be mounted on the vehicle chassis (20), allowing tyre squeal to be simulated when the vehicle brakes harshly or turns sharply. The vehicle itself is controlled in the usual way by levers mounted on the control transmitter unit.

Balanced impedance coupler

Abstract: A balanced preamplifier is disclosed for impedance-coupling an audio signal source, such as a microphone, to a differential amplifier. In one embodiment, the preamplifier comprises a first stage wherein a pair of complementary bipolar transistors are connected in a common-base configuration and coupled to a low-impedance microphone so that the microphone signal is appied to the respective emitters of the transistors and transformed to an appropriately higher impedance level at the respective collectors thereof with common-mode passage of external and internal noise. A second stage including a complementary pair of bipolar transistors in a common-emitter configuration is coupled to the first stage for greater power and voltage amplification requirements. In a second embodiment, the preamplifier comprises a pair of complementary field-effect transistors (FET) connected in a series common-drain configuration and coupled to a high-impedance microphone so that the microphone signal is applied to the respective gates of the FETs and transformed to an appropriately lower impedance level at the respective sources thereof with common-mode passage of noise.

Dual section electret microphone

Abstract: A bi-directional capacitor microphone is formed of first and second transducer sections, each section comprising a diaphragm and a back plate facing the diaphragm and separated therefrom. The diaphragm of the first transducer section includes an electret and the back plate of the second transducer section includes another electret. The back plates of the first and second transducer sections are disposed in a back-to-back configuration and are electrically coupled to each other and to one output. The diaphragms of the first and second transducer sections are connected to each other and to another output, so that an output signal appears between the outputs. Preferably, both electrets are selected to have a negative polarity. The bi-directional microphone so constructed exhibits superior response for lower audio frequencies.

Arcuately tensioned piezoelectric diaphragm microphone

Abstract: A lightweight piezoelectric microphone using a metallized piezoelectric diaphragm arcuately bowed by a boss on a slotted baffle plate held in close parallel proximity to the diaphragm is disclosed. Slotted Helmholtz resonators provide frequency response shaping and wide band noise cancellation. Electrical contact between the diaphragm and an electrical conductor is provided by a conductive, elastic material compressed by parts of the microphone housing, into electrical contact with the conductor and a metallized side of the diaphragm.

Circuit arrangement for a telephone apparatus

Abstract: 1. Circuit arrangement for a telephone apparatus having a speech recognition and evaluation unit (AW) connected with a microphone (M), which converts spoken words characterizing numerical values and commands for example in binary numerical values or command words and forwards the numerical values to a transmitter for dial pulses (S), where-upon a dial number is transmitted automatically in the terminal line (a/b) of the telephone apparatus triggered by a command word, whereby the speech recognition and evaluation unit (AW) has a memory (SSP) with the characteristical sound pattern of the numerical values and the command words, and the recognition of the spoken numerical values and commands is performed by the comparison of the sound pattern of those with the stored sound pattern, characterized in, that in the speech recognition and evaluation unit (AW) the individual sound pattern of one or several numerical values significant to one or several persons are stored additionally to the characteristical sound pattern, that these sound pattern are also used for comparison and that the transmission of a dial number is only performed, if the individual sound pattern of one or several digits of the dial number correspond with the concerning sound pattern of the spoken numerical value.

Automatic musical tuning device

Abstract: An electronic automatic musical tuning device whereby an incoming tone from a musical instrument is picked up by a microphone, amplified and transformed to a square wave signal and compared in a phase locked loop with a progressive series of standard frequencies until matching occurs and the loop is locked to enable a display of the tone in a convenient output such as a row of lights.

Electromagnetic forming apparatus

Abstract: PURPOSE:To make the simultaneous execution of the forming work and the discrimination of propriety of this forming work to be possible, by installing the inspection apparaus consisting of the forming sound detector and the forming sound analyzer, in the titled apparatus comprising the coil connected to the electric impulse current generating circuit and the field shaver. CONSTITUTION:For example, at jointing the heat exchanger tubes 3, 4, the end of the tube 3 is inserted into the diameter expanded part of the tube 4, and this tube end assembly is inserted into the field shaver 2. The control circuit 14 for the electric power source generates the electric impulse current, and the tubes are perfectly jointed, if the magnetic field, etc., of the coil 1 are free from the defects. However, if the tubes possess the defects like as the burr at their ends, the excessively large or small wall thickness, the wall thickness deviation, the excessively large deviation of the physical property, the existence of flaws and soils, etc., the anomaly is caused in the acoustic spectrum to be generated at performing the electrodischarge machining work and in the variation with time of this acoustic spectrum. This impulse sound is caught by the microphone 15 and is inputted to the discriminating circuit 25, which discriminates the propriety of the machining work depending on the data of the sound-pressure level of the respective frequency component at each point of time; according to this result of discrimination, the propriety display circuit 26 displays the propriety of the work.