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Showing papers on "Microphone published in 1970"


Patent
02 Dec 1970
TL;DR: In this paper, a hearing aid structure is provided in which all of the components of the hearing aid may be fitted within a person''s ear, including a main housing for a power source and an amplifier, isolated from the main housing and connected to it by a deformable, flexible, skeletal structure.
Abstract: A hearing aid structure is provided in which all of the components of the hearing aid may be fitted within a person''s ear. The structure includes a main housing for a power source and an amplifier and a microphone housing isolated from the main housing and connected to it by a deformable, flexible, skeletal structure. A receiver is compliantly connected to the main housing and an ear seal is rigidly coupled to the receiver and adapted to fit snuggly into the ear canal of a person''s ear.

46 citations


Journal ArticleDOI
TL;DR: In this article, a technique for combining the signals from two or more microphones to produce a single output having less multipath distortion than any of the individual microphone signals is described, where the output from each microphone is filtered to separate it into a number of bandpass signals occupying contiguous frequency bands.
Abstract: The transmission between a sound source and a microphone in a small hard‐walled room is characterized by multiple peaks and sharp valleys. Sound received by such a microphone often is judged to be undesirably distorted or spectrally colored. A technique is described for combining the signals from two or more microphones to produce a single output having less multipath distortion than any of the individual microphone signals. The output from each microphone is filtered to separate it into a number of bandpass signals occupying contiguous frequency bands. The microphone with greatest long‐time response in a given frequency band contributes that band to the output. Each microphone, then, is used only for those frequency bands in which its response is greater than any other microphone, so that the combined output contains less spectral coloration than the signal from any individual microphone. The performance of the process was studied by simulation on a digital computer, and sample recordings are included.

30 citations


Patent
28 Oct 1970
TL;DR: In this paper, a digital display hearing aid gain analyzer is provided for measuring the gain of hearing aids over a predetermined frequency range, which is then displayed on Nixie tubes.
Abstract: A digital display hearing aid gain analyzer is provided for measuring the gain of hearing aids over a predetermined frequency range. A sine wave oscillator generates a predetermined sine wave frequency in an anechoic chamber. The hearing aid to be tested is then connected in the chamber to a microphone pickup housed in a 2 cubic centimeter coupler and picks up and amplifies the sine wave signal in the chamber which is then converted from a linear sine wave signal to a logarithmic signal to a digital type signal indicative of the gain of the hearing aid which is then displayed on Nixie tubes.

26 citations


Patent
01 Apr 1970
TL;DR: Guitars and similar plucked-string instruments are provided with a microphone-holding attachment at a corner adjacent the neck of the instrument as discussed by the authors, which frees a singer-player from dependence on a stationary microphone.
Abstract: Guitars and similar plucked-string instruments are provided with a microphone-holding attachment at a corner adjacent the neck of the instrument. This frees a singer-player from dependence on a stationary microphone.

25 citations


Patent
07 May 1970
TL;DR: In this paper, a vibratory flexible diaphragm receiving sound pressure of sound signals on one of its surfaces, wherein a small plane mirror is secured to the other surface, is included in an optical interferometer energized by a light source and having two propagation paths.
Abstract: A microphone for converting sound vibrations into a train of electrical pulses and comprising a vibratory flexible diaphragm receiving the sound pressure of sound signals on one of its surfaces, wherein a small plane mirror is secured to the other diaphragm surface; the mirror is included in an optical interferometer energized by a light source and having two propagation paths, one of which is of fixed length and the other of which has a length varying in dependence upon time in accordance with the instantaneous position of the mirror and diaphragm; the light wave trains transmitted by the paths interfere in a chosen region of the interferometer to produce at least one sequence of images whose luminosity varies in dependence upon the variable path length; and such images are received by at least one photodiode delivering electric signals which are subsequently converted into a train of electric pulses.

23 citations


Patent
14 Sep 1970
TL;DR: In this paper, the authors proposed an apparatus for monitoring the noise level of passing vehicles and automatically photographing a vehicle which emits noise that exceeds a predetermined threshold level, which includes a vehicle sensor which acoustically determines when a passing vehicle reaches a chosen target area.
Abstract: An apparatus for monitoring the noise level of passing vehicles and for automatically photographing a vehicle which emits noise that exceeds a predetermined threshold level. The apparatus includes a vehicle sensor which acoustically determines when a passing vehicle reaches a chosen target area. In a preferred embodiment of the invention the vehicle sensor includes a pair of microphones and an acoustic delay line which feeds one of the microphones. The microphone outputs are correlated to determine when the vehicle enters the target area.

15 citations


Patent
21 May 1970
TL;DR: An ultrasonic wave microphone which comprises a flat piezo-electric vibrator and a funnel-like appendant resonator formed of a metal having a high Q and connected to the vibrator at the center thereof is especially useful for a remote control device or the like for a television set as mentioned in this paper.
Abstract: An ultrasonic wave microphone which comprises a flat piezo-electric vibrator and a funnel-like appendant resonator formed of a metal having a high Q and connected to the piezo-electric vibrator at the center thereof so that electrical characteristics of the microphone can be varied, and which is especially useful for a remote control device or the like for a television set.

15 citations


Patent
01 Jun 1970
TL;DR: The microphone of as mentioned in this paper obtains damping from a perforated baffle closely adjacent the diaphragm with fabric covering the perforations, and from resistive structures behind the baffle.
Abstract: The microphone of the invention obtains damping from a perforated baffle closely adjacent the diaphragm with fabric covering the perforations, and from resistive structures behind the baffle. The piezoelectric transducer element is mounted directly on a circuit board which also carries all electronic components of a preamplifier circuit.

14 citations


Patent
05 Nov 1970
TL;DR: In this article, a U-shaped supporting pedestal is rotatably and frictionally secured at its bight portion to a support member attached to the earphone of a headset.
Abstract: A U-shaped supporting pedestal is rotatably and frictionally secured at its bight portion to a support member attached to the earphone of a headset. The limbs of the pedestal extend outwardly from the support member and are slotted to receive an elongated microphone arm which is longitudinally displaceable through the slots. Further, the arm can be positioned by rotating the pedestal on the support member and by laterally displacing the arm within the slot in one limb while it is held in frictional engagement within the slot in the other limb.

14 citations



Patent
24 Feb 1970
TL;DR: In this paper, a transducer is modulated by the application of mechanical stress to the channel layer of the device, where the source is a preamplifier in either discrete or integrated circuit form.
Abstract: A transducer apparatus wherein the source to drain conductance of an insulated gate semiconductor field effect device is modulated by the application of mechanical stress to the channel layer of the device. Specific transducer modifications include microphone pickups and phono-pickups. The pickup may include preamplifiers in either discrete or integrated circuit form.

ReportDOI
01 Jul 1970
TL;DR: In this paper, measurements were taken of the noise radiated from three sailplanes in order to define the aerodynamic noise and to determine its relation to aircraft size and velocity, and the report presented the results obtained from one microphone and relates the overall sound pressure level (SPL) to aircraft parameters.
Abstract: : The noise associated with a flight vehicle is generated by two distinct type sources: (1) the propulsion system and (2) the aerodynamic noise associated with movement of the vehicle through the atmosphere. The minimum noise will be radiated when the propulsion noise is eliminated. Measurements were taken of the noise radiated from three sailplanes in order to define the aerodynamic noise and to determine its relation to aircraft size and velocity. The report presents the results obtained from one microphone and relates the overall sound pressure level (SPL) to aircraft parameters.

Patent
12 Jan 1970
TL;DR: In this article, a microphone assembly includes a longitudinally elongated microphone capsule which is supported within a substantially cylindrical outer casing having an electrical wire connection entering the casing from one end.
Abstract: A microphone assembly includes a longitudinally elongated microphone capsule which is supported within a substantially cylindrical outer casing having an electrical wire connection entering the casing from one end. The microphone is provided with an acoustic inlet at the opposite end of the casing and it is supported in the casing at least at each end by a vibration absorbing support. The support isolates the microphone capsule from noise transmitted to the outer casing. The support at the acoustic inlet end of the microphone capsule comprises a resilient vibration absorbing annular molding which has an inward and radially extending inner end which bears against a collar of a cap which is fitted over the acoustic ends of the microphone. The outer periphery of the annular molding engages against the inner wall of the casing and is held in place by friction or by an adhesive. The cap includes an annular surface which is arranged over the end of the microphone capsule and it includes a collar forming a ''''Helmholtz resonator'''' together with an air chamber defined between the protective cap and the diaphragm of the microphone capsule. The molding holding the cap in position forms a funnel which opens outwardly and is engaged by a perforated cap and its associated ring nut at its outer end.

Patent
25 Sep 1970
TL;DR: In this paper, an improvement in a microphone used primarily in head-worn hearing aids in which the microphone achieves a directional characteristic is presented. But, the authors do not specify the type of microphones they used.
Abstract: The disclosure is directed to an improvement in a microphone used primarily in head-worn hearing aids in which the microphone achieves a directional characteristic. The chamber and aperture in front of the diaphragm or other speech-responsive member is constructed in the normal manner while the chamber to the rear of the diaphragm or other speech-responsive member has a plurality of hollow elongated members secured within the walls of the microphone housing. The elongated members may be formed from sintered porous material such as metal, glass, or plastic, and may be arranged side-by-side or in a honeycomb arrangement. The elongated members attenuate the propagation of the sound waves, the attenuation being approximately 20 decibels lower than that reaching the other side of the diaphragm or other speech-responsive member without materially changing the inherent response characteristic of the microphone.

Patent
21 Sep 1970
TL;DR: In this paper, a noise-cancelling microphone with a differential diaphragm assembly is presented, in which a small inner diaphrasm is mounted on one end of a hollow, sound conducting acoustic tube that has an electroacoustic transducer mounted on its other end for translating sound conducted through the tube into corresponding electrical signals.
Abstract: A noise-cancelling microphone in which a differential diaphragm assembly is mounted on one end of a hollow, sound conducting acoustic tube that has an electroacoustic transducer mounted on its other end for translating sound conducted through the tube into corresponding electrical signals. The differential diaphragm assembly includes a small, inner diaphragm which seals off the end of the acoustic tube and a larger, outer diaphragm which is mounted in front of the inner diaphragm and is connected in its central region to the central region of the inner diaphragm. The outer diaphragm is exposed on both surface to the ambient atmosphere so as to receive sound waves on both its inner and outer surfaces, thereby acting as a noise-cancelling element in which background noise or distant sounds that impinge on one side of the diaphragm will be cancelled out by the same noise or sound impinging on the other side of the diaphragm. Nearby vocal sounds will, however, be picked up by the outer diaphragm since these sounds produce a substantial differential of pressure across the diaphragm. The vocal sounds picked up by the outer diaphragm are conducted by mechanical coupling to the inner diaphragm and from there down the acoustic tube to the electroacoustic transducer.

Patent
01 May 1970
TL;DR: In this paper, a cover of substantially cup-shaped configuration fits over one end of the microphone housing above the transducer and it is made of a material which comprises a plurality of particles which are sintered together or fused together in a manner to define tortuous passages therebetween and to define hollow spaces remaining between the particles, and which hollow spaces are interconnected, thus forming irregular channels which assure the sound permeability of the cap but are impenetrable by dust or other air pollutants.
Abstract: A microphone includes a microphone housing having a sound transducer therein. A cover of substantially cup-shaped configuration fits over one end of the housing above the transducer and it is made of a material which comprises a plurality of particles which are sintered together or fused together in a manner to define tortuous passages therebetween and to define hollow spaces remaining between the particles, and which hollow spaces are interconnected, thus forming irregular channels which assure the sound permeability of the cap but are impenetrable by dust or other air pollutants.

Patent
10 Apr 1970
TL;DR: An air permeable sound grating for sound shielding as discussed by the authors consists of, or includes, volume changing elements which are controlled by properly positioned means, such as a microphone orientated toward the noise source, to effect change in volume of an adjacent noise transmitting medium such as air.
Abstract: An air permeable sound grating for sound shielding. The grating consists of, or includes, volume changing elements which are controlled by properly positioned means, such as a microphone orientated toward the noise source, to effect change in volume of an adjacent noise transmitting medium, such as air, to effect such a anticyclic change in volume as to cause interference attenuation of the sound at the side of the grating facing away from the noise source. Such volume changing elements are spaced apart a distance less than the wavelength of the highest frequency sound to be shielded and may comprise a variety of means such as spaced heating wires, conductive coating upon a thermal and electrically insulating base, a closed capsule with membrane surfaces having vibration generating means operatively associated with said membrane, radiation generating means for discharging medium heating radiation of energy into the sound transmitting medium together with controls and reflectors for directing the volume changing means or energy to the desired zone to be shielded.

Journal ArticleDOI
TL;DR: In this paper, a very sensitive microphone suitable for acoustic measurements in liquid helium is described, and the first sound pressure response of the microphone and the second sound transmitter response can be measured by a special extension of the reciprocity theory.
Abstract: A very sensitive microphone suitable for acoustic measurements in liquid helium is described. With the use of it both, the pressure amplitude of second sound and the amplitude of first sound radiated from the second sound transmitter (carbon layer heater) can be detected. By a special extension of the reciprocity theory the first sound pressure response of the microphone and the second sound transmitter response can be measured. The measured pressure signals of first and second sound are compared with the results of the two-fluid theory.

Patent
24 Mar 1970
TL;DR: An improved structure for a dynamic vibration generator, such as a loudspeaker or a microphone, which includes stacked sheets of high permeability material in the area of the pole gaps to suppress eddy currents is described in this article.
Abstract: An improved structure for a dynamic vibration generator, such as a loudspeaker or a microphone, which includes stacked sheets of high permeability material in the area of the pole gaps to suppress eddy currents.

Patent
20 Oct 1970
TL;DR: In this paper, an inertial microphone is suspended within a helmet, for contact with the head, and the microphone is uniquely mounted to inhibit the physical transmission of ambient noise and vibration to it through its mounting.
Abstract: An inertial microphone is suspended within a helmet, for contact with the head. It is surrounded and shielded from external air turbulence. The microphone is uniquely mounted to inhibit the physical transmission of ambient noise and vibration to it through its mounting. One's face and hands remain unencumbered. Voice vibrations pass through the skull and head tissue, on to the microphone. Satisfactory speech communication is obtained even while in 100 knot winds and/or in noise levels up to 120 decibels. Useful in military, helicopter, fire and police operations.

Journal ArticleDOI
TL;DR: A comparative evaluation was done on the speech intelligibility of two hearing aids, one with an inductance loop and the other with a conventional body unit, finding the former to be more accurate than the latter.
Abstract: A comparative evaluation was done on the speech intelligibility of two hearing aids, one with an inductance loop and the other with a conventional body unit. Each aid received and reproduced 50 mon...

Patent
13 Nov 1970
TL;DR: In this article, a preamplifier placed in the coupler as close as possible to the microphone is used to amplify the microphone signals before they are subjected to noise or other interference in the wires leading to the receiving machine.
Abstract: In a facsimile system, an acoustic coupler is used to connect a facsimile machine through a telephone handset to a telephone line and a remote machine. When a machine is receiving, audible signals at the earpiece of the telephone handset are directed toward a microphone which is wired to the machine. The signal-to-noise ratio of received signals is improved by a preamplifier placed in the coupler as close as possible to the microphone. The preamplifier amplifies the microphone signals before they are subjected to noise or other interference in the wires leading to the receiving machine.

Patent
22 Jul 1970
TL;DR: In this article, the authors describe an apparatus consisting of a microphone and a moving coil loud-speaker coupled by an amplifier, where phase change occurs in the amplifier or by making appropriate loudspeaker connections.
Abstract: 1,199,925. Noise reduction. MIDLAND TRANSFORMER CO. Ltd. 22 Nov., 1967 [8 Sept., 1966], No. 40157/66. Heading H4J. In reducing noise emitted by a source, sound waves are picked up adjacent the source, a signal is generated from the sound waves, and sound waves are reproduced adjacent the source at approximately the same amplitude and frequency as the emitted sound waves and approximately 180 degrees out of phase with the emitted sound waves. The apparatus comprises, adjacent a source 10 (Fig. 1), a microphone 11 and moving coil loud-speaker 15 coupled by an amplifier 13. Phase change occurs in the amplifier 13 or by making appropriate loud-speaker connections. Alternatively, adjacent a source 16 (Fig. 2) are a microphone 17 and " Stentorphone " device 19 coupled by an amplifier 18 in which phase change occurs. In the device 19 pulsating blasts of compressed air from a source 20 are released into a horn by a valve 22 vibrated by electromagnetic means (not shown) in sympathy with the signal to be reproduced. Reduction of noise caused by a mechanical saw or by aircraft at an airport may be effected.

Patent
03 Sep 1970
TL;DR: In this paper, a microphone assembly in which a piezoelectric transducer beam is attached at one end to a flexible diaphragm and is supported at the other end by simply resting upon an electrical contact without being connected thereto is described.
Abstract: A microphone assembly in which a piezoelectric transducer beam is attached at one end to a flexible diaphragm and is supported at the other end by simply resting upon an electrical contact without being connected thereto. The transducer beam is pressed against the supporting contact by a second electrical contact that is shaped to support the transducer beam near its center and to apply a rotary force thereto. The second electrical contact has a rectangular opening formed in an end portion thereof for receiving and supporting the transducer beam and the end portion of the electrical contact beyond the rectangular opening is rolled over to form a spring for applying rotary force to the transducer beam.

Patent
28 Oct 1970
TL;DR: In this article, an unmodulated sound source is modulated by movement of a dumb person's lips, mouth and tongue and is amplified, while a differential amplifier cancels the noise generated by the user's mouth when a mouthpiece is held in front of a user's lips.
Abstract: 1,213,521 Dumb aid GEORGE WASHING- TON Ltd 31 March, 1969 [6 Jan, 1968], No 969/68 Heading H4J An unmodulated sound source is modulated by movement of a dumb person's lips, mouth and tongue and is amplified, while a differential amplifier cancels the unmodulated sound A sound source I includes a random noise generator 1 and a loud-speaker 5 projects noise into a user's mouth when a mouthpiece 7 is held in front of the user's lips A microphone 6 detects the user's speech signals Its output is connected via a pre-amplifier 8 to one input of a differential amplifier 10, the other input of which is connected to the output of a push-pull amplifier 4 in the sound source I through a buffer stage 9 The output from the differential amplifier 10 is fed via an output stage 11 to a second loud-speaker 12 All components including a battery 13 are in a single housing 7 and a pressswitch 14 in a hand-grip incorporates a volume control, preferably of the two or three position type so that increased pressure means increased output The output from the differential amplifier 10 is pure speech, the background of unmodulated speech being cancelled out Thus the buffer stage 9 has a pre-set gain and is adjusted in phase and gain so that its output approximates as closely as possible to the background signal detected by the microphone Instead of a buffer amplifier 9 there may be employed two separate microphones, one to detect the speech signals plus background and the other to detect background alone Alternatively a stereophonic type microphone may be used A single tone generator or buzzer may replace the sound source I Output terminals for direct connection to a tape recorder or telephone adapter may be provided The housing 7 may comprise a plastics mouthpiece with loud-speaker 5 and microphone 6 side by side but separated by a wall A flexible shroud contacting the user's cheeks may be used out of doors A coaxial construction of loud-speaker and microphone provides maximum sensitivity The sound source is described in Specification 1,210,171

Journal ArticleDOI
TL;DR: In this article, the presence of thermal-acoustic noise was detected and measured in a high sensitivity ribbon velocity microphone, and the theoretical and experimental data correspond for both the thermal electric noise and the thermal acoustic noise.
Abstract: In electrodynamic microphones, there are two major sources of thermal agitation noise, namely, the electromotive force due to the thermal agitation of the electrons in the conductor and the electromotive force produced by the motion of the diaphragm due to the thermal agitation of the molecules impinging upon the diaphragm. In commercial microphones, the thermal‐acoustic noise is far below the thermal‐electric noise. Therefore, in order to detect the thermal‐acoustic noise, a special high‐sensitivity ribbon velocity microphone was designed and built. The presence of the thermal‐acoustic noise was detected and measured in this microphone. The theoretical and experimental data correspond for both the thermal‐electric noise and the thermal‐acoustic noise.

Patent
16 Nov 1970
TL;DR: In this paper, the vibrations of a membrane are read out by means of a pulsed light beam incident on a photoelectric sensor, and an integrated sensor amplifier structure is used.
Abstract: The vibrations of a membrane are read out by means of a pulsed light beam incident on a photoelectric sensor. Integrated sensor amplifier structures are used.

Journal ArticleDOI
TL;DR: In this article, the axial sensitivity of a porous pipe microphone is found to be unity when the microphone element has a high acoustic impedance, and the filtering action of the porous pipe microphones for the turbulent boundary layer noise is calculated for a simple model of flow noise.
Abstract: A porous pipe allows weak coupling between acoustic pressures outside and inside the pipe. A single microphone element is located at one end of the porous pipe. Only the waves traveling towards the microphone are preserved; the porous pipe includes a solid internal cone, which produces an anechoic termination for waves traveling in the opposite direction. The design yields the specific flow resistance of the porous pipe and the cone shape for the anechoic end. The axial sensitivity of the porous pipe microphone is found to be unity when the microphone element has a high acoustic impedance. The directivity follows that of a uniform line with uniform delays. The filtering action of the porous pipe microphone for the turbulent‐boundary‐layer noise is calculated for a simple model of flow noise. Experimental values of microphone sensitivity, directivity, and flow‐noise rejection are presented. [This work was initiated and supported by the Systems Application Division of U. S. Army MERDC, Fort Belvoir, Virgini...

Patent
19 Oct 1970
TL;DR: A portable lecturn consisting of a hinged lecturn platform support constructed and arranged to be locked into the latching mechanism of an open hinged container such as an attache case, whereby a rigid, box-like housing affording access to sound receiving and transmitting equipment there within and mounting a microphone stand assembly is provided.
Abstract: A portable lecturn consisting of a hinged lecturn platform support constructed and arranged to be locked into the latching mechanism of an open hinged container such as an attache case, whereby a rigid, box-like housing affording access to sound receiving and transmitting equipment therewithin and mounting a microphone stand assembly is provided. When not in use, the hinged platform-support folds and is stored within the case along with the microphone stand assembly and the sound receiving and transmitting equipment.

01 Jan 1970
TL;DR: In this paper, the cross-spectral matrix diagonal removal (DR) and de-reverberation were used to improve the accuracy of closed-section wind tunnel measurements.
Abstract: Closed-section hard-walled wind tunnels are routinely used for aerodynamic testing during the early stages of vehicle design. The use of microphone arrays and beamforming processing in such environments can yield useful source localisation information; yet there are concerns as to the consistency of quantitative results from such methods when compared to anechoic openjet tunnel testing. Higher background noise levels, microphones in contact with the turbulent boundary layer, and the highly reverberant nature of the measuring environment are of particular concern. In this paper we show that accurate results in closed-section wind tunnels are still possible using the cross-spectral matrix diagonal removal (DR) technique, and with dereverberation. With DR, improvements in beamformer’s accuracy up to 10 dB can be achieved when compared to standard beamforming. De-reverberation gives an additional 10 dB improvement, and provided that the noise contamination to the microphone pressure data is somewhat suppressed, errors within §1dB can be expected. Both of these methods do not require any additional changes to the physical infrastructure of the measuring environment.