Showing papers on "Microphone published in 1985"

Computer-steered microphone arrays for sound transduction in large rooms

Abstract: The quality of sound pickup in large rooms—such as auditoria, conference rooms, or classrooms—is impaired by reverberation and interfering noise sources. These degradations can be minimized by a transducer system that discriminates against sound arrivals from all directions except for that of the desired source. A two‐dimensional array of microphones can be electronically beam steered to accomplish this directivity. This report gives the theory, design, and implementation of a microprocessor system for automatically steering a two‐dimensional microphone array. The signal‐seeking transducer system is implemented as a dual‐beam, “track‐while‐scan” array. It utilizes signal properties to distinguish between desired speech sources and interfering noise. The complete automatic system has been tested in anechoic and medium‐sized auditorium environments, and its performance is discussed.

Active sound attenuation system with on-line adaptive feedback cancellation

Abstract: An active acoustic attenuation system (2) is provided for attenuating an undesirable output acoustic wave by introducing a cancelling acoustic wave from an omnidirectional speaker (14) at the output (8), and for adaptively compensating for feedback from the speaker (14) to the input (6) for both broad band and narrow band acoustic waves, without pre-training. The feedback path (20) is modeled with a single filter model (40) adaptively modeling the acoustic system (4) on-line without dedicated off-line pre-training, and also adaptively modeling the feedback path (20) from the speaker (14) to the input microphone (10) on-line for both broad band and narrow band acoustic waves without dedicated off-line pre-training, and outputting a correction signal to the speaker (14) to introduce a cancelling acoustic wave.

Remote control hearing aid

Abstract: A hearing aid with wireless remote control of at least one of its controllable functions. The microphone of the hearing aird is used as a receiving element for the control signals. Energy (such as ultrasound) which the hearing aid microphone can transform into electrical signals which are separated from the other signals in a remote control part and caused to act upon the control members is used as a control signal transmission medium. Equipping a hearing aid with a remote control according to the invention is suited in particular for miniature hearing aids and for hearing aids insertable into the ear canal.

Vehicle voice recognition method and apparatus

Abstract: A voice actuated control system for a motor vehicle. A microphone mounted to the vehicle senses user commands as well as other noise in the passenger compartment. Analog electrical signals from the microphone are converted into digital form and compared by a high speed microprocessor with a user profile. A correspondence between the profile and the sensed input causes a control function such as raising or lowering a window to be performed. A speech synthesizer in the system prompts the user in the event a command in a command sequence is inappropriate.

Gain switched audio conferencing network

Abstract: An audio conferencing system includes a plurality of remote stations (10) which are interconnected in a conference mode through a central switching network (66) through communication lines (16). Each of the remote stations has a microphone (34) and a speaker (64) associated therewith. The microphone (34) on each of the remote stations has a voltage controlled amplifier (VCA) (59) associated therewith and the speaker (64) has a VCA (60) associated therewith. A CPU (48) selectively controls the output of the microphone (34) to selectively decrease the gain thereof when voice is not detected. When voice is detected above a predetermined threshold, the microphone (34) is allowed to operate at full gain and the speaker (64) has the output level thereof decreased. This effectively reduces the audio loop gain between remote stations in a conference.

Headphone with sound pressure sensing means

Abstract: Headphones have a small cavity between the diaphragm and the ear canal with a microphone in the cavity closely adjacent to the diaphragm slightly off the axis of the ear canal and headphone diaphragm with the microphone membrane perpendicular to the headphone diaphragm. The microphone provides a feedback signal that is combined with the input electrical signal to be reproduced by the headphones to provide a combined signal that is power amplified for driving the diaphragm. The headphone transducer has a small 23 mm diameter diaphragm with a maximum excursion of 0.6 mm peak-to-peak and a low frequency resonance of 200 Hz. A disk of intracavity damping material inside the cavity isolates the microphone from the ear canal.

Device for interrupting the snoring of a sleeping person

Abstract: A device is provided for interrupting the snoring of the subject as soon as it starts. Said device comprises a microphone (2) for picking up the noise emitted by the subject, and means (3) for comparing the intensity of the noise picked up by the microphone (2) with a given alarm threshold. It is characterized by the fact that it further comprises means (6) which, should the alarm threshold be exceeded, emit for a given brief time a sound stimulus of an intensity sufficient to be perceived by the subject but insufficient to awaken him.

Speech recognition control system and method

Abstract: A weighing scale involving calculating functions is provided with an automatic control system that can accept words of speech spoken into a microphone as inputs to the automatic control system.

Processor controlled ear responsive hearing aid and method

Abstract: A processor controlled ear responsive hearing aid for the ear of a hearing impaired individual and method for operating a hearing aid. The input from the microphone is amplified and split into a plurality of band-pass channels each having a frequency range of approximately one-third octave. Each channel has an amplifier that is controlled by the processor. The processor receives control signals from a feedback microphone located in the ear canal and uses the control signals to develop a spectrum of the actual sound pressure levels by frequency at the eardrum. The processor compares averages of the actual sound pressure levels to the desired levels for each channel and for the overall output according to a predetermined set of instructions and controls the channel amplifiers and an output amplifier to produce the desired sound pressure levels for each frequency in the ear canal.

Information transmission system

Abstract: 1,235,481. Signalling by audio-frequencies. BRITISH AIRCRAFT CORP. Ltd. 12 March, 1969 [19 Dec., 1967], No. 57589/67. Heading G4H. [Also in Division H4] In a system for signalling between a central station and a number of remote gun stations by radio telephone or over telephone lines the central station has a microphone and an encoder adapted to accept a decimal input and produce a binary coded output the "1" and "0" bits of which are represented by two audio-frequency tones, means being provided to transmit either the output from the microphone or the output from the encoder and means at the receiver to reproduce either speech or the original decimal input. The decimal input, from a computer for a keyboard, is applied to the encoder and a switch passes it to the transmission circuit. The signals are gated into a shift-register in the encoder under the control of clock pulses. A counter gives a signal when the message is complete to switch the transmission back to the microphone. At the gun station the two frequencies are separated by filters, the output of the "1" filter being applied to a call recognition circuit which enables the decoder. This comprises a shift register into which the incoming serial signals are shifted under the control of clock pulses derived by combining the outputs of the "1" and "0" filters. The output of the shift register is recoded from binarycoded-decimal form into decimal form and displayed on indicators showing the azimuth and bearing to which the gun is to be laid. Speech signals are reproduced on a speaker.

Method of and means for adaptively filtering screeching noise caused by acoustic feedback

Abstract: A communication system, such as a hearing aid or a public address system, may include a microphone for inputting audio information to the system, an amplifier for amplifying audio frequency signals inputted to the microphone, and a speaker for outputting amplified audio frequency signals into the environment which provides an acoustic feedback path between the speaker and the microphone. The invention provides an identification circuit for dynamically identifying those parameters associated only with acoustic feedback, and a correction circuit whose transfer function is established in accordance with the parameters identified by the identification circuit. The transfer function of the correction circuit is such that the effect of acoustic feedback is cancelled from the transfer function of communication system. The identification circuit is constructed and arranged to identify said parameters in response to a turn-on of the system, or to an automatically-sensed threshold change in gain of the amplifier.

Unidirectional second order gradient microphone

Abstract: A second order gradient microphone Fig. 1 with unidirectional sensitivity pattern is obtained by housing each of two commercially available first order gradient microphones 14, 24 centrally within a baffle 12, 22. The baffles have flat surfaces, are preferably square or circular and have parallel surfaces the two baffles being parallel to each other. The rotational axes of the microphones are arranged to coincide. The output signal from one of the microphones is substracted from the delayed signal output of the other.

Design and function: a physical and electrical description of the 3M House cochlear implant system.

Abstract: A patient-wearable, single-electrode cochlear implant was first used by a patient in 1972 at the House Ear Institute. Since early 1982, a redesigned version of this system has been in clinical use. This new system, called the 3M House cochlear implant system, consists of an implanted receiver and a patient-worn signal processor, transmitter, and microphone. Also available are instruments to assist the audiologist and patient in proper fitting and testing of the equipment. Physical and electrical characteristics of the devices are described, with attention given to improvements over the older system and features important to the use in children.

Apparatus for the photoacoustic detection of gases

Abstract: The apparatus for detecting gases comprises a photoacoustic gas detector 35, in which the intensity-modulated absorbed test light beam 32' is converted into noise and detected by means of microphone 36 The photoacoustic gas detector 35 is acoustically decoupled from the gas collecting point 54 by a gas-permeable diaphragm 52 or a rigid, porous material 52' The gas chamber 35' of photoacoustic detector 35 can be scavenged by means of supply lines 38, 38' and valves 56, 56' It is advantageous to use a thermal source 32 intensity-modulated by phase lag The signal is processed at microphone 36 by means of a N-path filter comprising cyclic switch 63 and R-elements 62, 65, 65' The apparatus can be used for detecting CO 2 and CO

Vocal tactile feedback method and associated apparatus

Abstract: A vocal tactile feedback apparatus and method for use in the treatment of stuttering and other speech or hearing abnormalities is disclosed. A microphone and amplifier are utilized to produce and amplify an electronic signal responsive to vocal utterances spoken within a known range of the microphone. The amplified signal is then delayed by a suitable delaying circuit for a desired time interval and is then transmitted to an electro-mechanical transducer attached to the outer surface of the laryngeal or glottis region of the neck of a user. The transducer then transforms the amplified delayed signal into a mechanical vibration to provide delayed vibrotactile feedback of the vocal utterances whether spoken by the user or by others. A unique transducer assembly for use in the apparatus and method is disclosed.

Microphone wind shroud

Abstract: A microphone wind shroud having a integral mounting means for being slidably mounted to an omnidirectional or unidirectional microphone, such as those integrally mounted on video cameras. A semi-rigid grid-like external shell shrouds the microphone head. The shell is lined with a multilayer laminate fabric material. The shell and laminate allow desired audio frequencies to pass and reach the microphone head while attenuating undesired wind noises caused by microphone movement or environmental wind conditions.

Digital loudspeaking telephone

Abstract: A digital loudspeaking telephone for connection to a telephone line, including a microphone, speaker, codec and digital signal processor. Incoming and outgoing signals are received by the digital signal processor from remote and local subscribers via the telephone line and microphone respectively. The processor generates and compares incoming and outgoing envelope and noise floor signal levels derived from the received incoming and outgoing signals and in response suppresses a particular compared, and one of the incoming or outgoing signals. Automatic gain control of outgoing signals is implemented in order to allow smooth switching of the outgoing signals and to suppress background noise from being transmitted by the microphone. Room echo and reverberation are also detected, and the processor eliminates spurious channel switching due to the detected echo signals.

High sensitivity stethoscopic system and method

Abstract: A lightweight, improved precordial suction stethescope constant monitoring system including a heart and breath sound detection means, solely mounted to patient using only suction or other connection means, and an inexpensive radio wave transmission means and a remote radio wave receiver and audio means. A quick connect suction cup or other stethescope, which is especially suitable for use on the wet skin of a newborn, is used to provide the acoustical recess of the stethescope head. A microphone transducer located in the stethescope head or in a detachable housing is used for converting acoustical vibrations into an electrical impulse. The said remote radio wave receiving means amplifies and converts the electronically transmitted physiological condition information into an audible signal. This system allows the attending medical personnel to be totally free of any physical connection to the patient being monitored.

Target system for laser marksmanship training devices

Abstract: A target system for laser marksmanship training devices is comprised of one or more photodetectors mounted on a target and sensitive to one or more pulses of the operating wavelength of a laser beam simulating the projectile of a weapon An amplifier increases the power output of the photodetectors, and a frequency selective transducer is operated from the amplified output of the photodetectors The transducer is attached and acoustically coupled to the target and produces a vibration signature simulating the vibration characteristics of a weapon-fired projectile striking the target A microphone sensitive to the vibration signature of the transducer is acoustically coupled to the target, and a drive mechanism lowers the target out of the field of view of the weapon when the microphone receives a hit-indicating vibration signature from the transducer In a preferred embodiment the laser pulses include a code sequence identification of the weapon being fired and the amplifier includes a decoder for the pulse code sequence The decoder includes a dual signal threshold level comparator in which a pulse signal level exceeding the first threshold level is established for a man target, and a pulse signal level exceeding the second threshold level is established for a vehicle target whereby the transducer is energized to initiate lowering of the target

Door message apparatus with telephone answering device

Abstract: A door message apparatus has a control unit which responds to operation of a doorbell switch to connect a door speaker/microphone to an automatic telephone answering and recording machine. The control unit applies a ring signal to the answering machine so that the machine then plays back a prerecorded message which is broadcast to the door caller. After the playback, the door caller may talk into the door speaker/microphone to produce a message which is recorded by the answering machine.

Hearing aid to be worn behind the ear

Abstract: The invention is based on the object of developing a hearing aid to be worn behind the ear in such a manner that it is possible to standardise hearing aids of different dimensions. This object is achieved by the fact that the hearing aid housing is divided transversely to its longitudinal axis into a first housing section (12) of fixed dimensions and into a second housing section (13) of variable dimensions. These two housing sections are mechanically and electrically connected to one another. The first housing section preferably contains the microphone, the receiver and the amplifier circuit and the second housing section (13) contains a battery (21) for supplying the hearing aid circuit with power. The second housing section (13) exists in various dimensions so that, for example, a larger battery (31) or other components, for example a mounted circuit board (32) can be accommodated within the second housing section (30). The drawing shows a hearing aid divided into two housing sections (12, 13).

Remote hearing aid volume control

Abstract: A hearing aid comprises a microphone, a battery-operated earphone, and amplifying circuit connected to the microphone output, the amplifying circuit including a frequency-selective circuit component and a sound level adjustment circuit component connected to the frequency-selective circuit component, and a remote sound wave control signal emitter circuit separate from the microphone, earphone and amplifying circuit and emitting sound wave control signals within the range of the microphone input.

Receiver for audible alarm

Abstract: A receiver to detect the audio tone emitted by an activated smoke alarm. The receiver employs an electret condenser microphone to monitor ambient sound. The output of the microphone is applied to an active band-pass filter and then to a PLL tone decoder. The PLL is tunable to provide maximum sensitivity to the frequency of the tone. The microphone is the gain controllable element in an AGC system that acts to keep received signals at a constant level. This insures that all devices operate linearly.

Damping for directional sound cancellation

Abstract: Sound in ducts can be reduced by using two cancelling sources spaced along the duct, and in order to reduce reflections upstream of the cancelling sources, sounds from these sources may be arranged to be in phase opposition upstream from the sources at all frequencies. Such an arrangement does not provide cancellation downstream at some frequencies. In the invention sound detected by a microphone is processed to generate a drive signal for a first source which tends to cancel sound in the duct partially, the remainder of the cancellation being provided by a sound source. A delay positioned between the sources is such that sounds from these sources are in phase at all frequencies of interest downstream of the second source.

The hearing aid feedback path: mathematical simulations and experimental verification.

Abstract: Acoustic feedback in hearing aids has received little attention in the literature. Feedback occurs when stability conditions of the open‐loop transfer function of an in situ hearing aid are violated. Solving the feedback problem will first require knowledge of the open‐loop transfer function. Included in the open‐loop transfer function is the acoustical path by which sound emanating from the earmold vent returns to the microphone (i.e., the feedback path). Reported herein are two different mathematical procedures for simulating transfer functions of the feedback path of an eyeglass‐type hearing aid. In one procedure the vent exit was modeled as a point source of sound located on a flat plane, while it was treated as a point source on a sphere in the other. Results of laboratory experiments indicate that the mathematical models accurately predict those acoustic phenomena for which they were intended: point sources on plane and spherical baffles. Results of manikin experiments showed both models to be less ...

Toy having a melody-making mechanism of a sound-detection type

Abstract: A toy, such as a stuffed doll, having a melody-making mechanism of a sound-detection type is disclosed, in which the melody-making mechanism is provided with a sound-detector, an amplifier circuit and a switching circuit in such arrangement that operation of the melody-making mechanism may be discontinued after a predetermined period of time. The sound-detector may be in the form of a ceramic condenser or a microphone.

Bandwidth design for speech-seeking microphone arrays

Abstract: Automatic delay-steering of uniform arrays of microphones, under control of on-site microprocessors, offers attractive possibilities for large-group teleconferencing. But, steering to wave-arrival directions away from the normal reduces the useable bandwidth over which spatial discrimination is achieved. This report, using the line array as the expository vehicle, derives relations that specify the useful bandwidth as a function of the steering direction, and gives design formulae for the number and spacing of the receiving elements.

Ear microphone utilizing vocal bone vibration and method of manufacture thereof

Abstract: This invention, directed to a displacement type bone vibration ear microphone possessing an electroacoustic transducer element planted in one of the end faces of a support member and a damper member formed so as to enclose therewith the electroacoustic transducer element, is characterized by disposing a flexible reinforcing member around or near the electroacoustic transducer element, allowing a free end of the electroacoustic transducer element and a outer end of the reinforcing member to be joined or juxtaposed to each other, and enclosing the periphery of the electroacoustic transducer element and the reinforcing member with the damper member thereby providing protection for the electroacoustic transducer element and heightening the efficiency of electroacoustic conversion.

Gas mask with voice communication device

Abstract: A face mask carries a voice communication device including a circular housing having voice transmitting openings and an annular seat which receives a flexible film diaphragm. The diaphragm is clamped to the seat by an inner circular member which has voice transmitting openings surrounding a socket for receiving a plug-in microphone. The housing receives an outer circular shield member which also has voice transmitting openings and defines a socket for receiving a plug on a microphone cord. Electrical conductor wires extend from the microphone socket through a passage around the diaphragm to the cord socket. A sealant material is injected into the passage and into an annular chamber which is defined between the housing and the inner microphone support member and receives a peripheral edge portion of the diaphragm.

Automatic graphic equalizer

Abstract: An automatic graphic equalizer for a sound system has circuitry for measuring the effect of the physical environment receiving a sound on the frequency characteristics of the sound, and for adjusting the characteristics of a graphic equalizer to compensate for distortions in the desired flat frequency response caused by the physical environment. The circuitry includes a pink noise generator supplying pink noise to the graphic equalizer during an initialization operation, the graphic equalizer being controlled by a controller to present a flat frequency characteristic. The equalizer output is sent to a speaker which supplies the pink noise as a sound signal to the selected environment. A microphone picks up the sound in the selected environment and converts it to an electrical signal which is supplied through an ALC amplifier to a frequency-variable band-pass filter to detect the signal level in each of the equalizer frequency bands. The level signals are smoothed in a level detector and digitized to be input to the controller which readjusts the graphic equalizer to compensate for distortions in the desired flat frequency response caused by the selected environment.