Showing papers on "Microphone published in 1973"

Feedback-cancelling electro-acoustic transducer apparatus

Abstract: Electro acoustic transducer apparatus having a loudspeaker and one or two microphones includes positional and/or electric arrangements for reducing or cancelling feedback from the loudspeaker. Also, a microphone apparatus has positional and structural features for reducing or cancelling echo.

Noise quality detector for electric motors or other machines

Abstract: Such detector is adapted to detect a transducer signal indicative of the level of noise, or the actual measured noise, produced by an electric motor or the like, particularly for the purpose of quality control in connection with a production line, automated or manual, so that motors which produce excessive noise or are defective may be identified and rejected. The detector employs an accelerometer or some other transducer, i.e. a microphone, for receiving the vibration or noise from each motor and converting the noise into electrical signals. After amplification, the signals are sent through a bandpass filter or a plurality of filters which selectively transmit those signals which are within a particular band of frequencies, while attenuating signals which are outside such band. The filter preferably has controls for adjusting both the upper and lower cutoff frequencies of the filter. The output signals from the filter are compared with a predetermined level. One or more indicating devices are operated by the comparison device to indicate whether the detected noise level is above or below such level. The indicating devices may be in the form of lamps or a meter. It is preferred to detect both the peak signal level and the average signal level so that the motor will be rejected if either level is above the desired level. The disclosed device is adapted to detect and indicate the noise quality of a plurality of motors in sequence on an automatic basis.

Control apparatus for sound reinforcement systems

Abstract: A control apparatus for a sound reinforcement system having plural audio input program microphones installed in a theater or like environment. The ambient sound or noise level in the environment is sensed and is employed to control each microphone individually so that a microphone is activated only if the audio material impinging thereon exceeds the ambient noise level. The audio output of the entire system is continuously and automatically adjusted so that the gain or amplification to which audio program signals are subjected is proportional to the number of program microphones that are active, thereby optimizing the operation of the system.

Microphone assembly operable in directional and non-directional modes

Abstract: A microphone assembly being selectively operable in directional and non-directional modes; and, having similar response characteristics relative to frequency whether operating in one or the other mode.

A Comparison Between Hearing Aids with Directional Microphone and Hearing Aids with Conventional Microphone

Abstract: In a double blindfold test 22 hearing impaired persons with a slight and moderate hearing loss have compared hearing aids with directional microphone to hearing aids with conventional microphone. A discrimination test in the sound—box showed a significant difference between the two types in favour of the hearing aid with directional microphone. A group conversation situation built up in a sound—box where the testpersons had the opportunity of comparing the two types of hearing aids also showed a significant difference. A comparison in a field test did not show corresponding results. The research project may indicate both pros et cons in connection with the hearing aid with the directional microphone. It was advantageous under critical listening conditions. Disadvantages occurred when the test persons heard sounds from behind. Furthermore there was a disturbing rubbing noise in this hearing aid.22 horehœmmede med lette og moderate horetab har i et dobbelt blindforsog sammenlignet hore—apparater med retning...

Animal training device

Abstract: An apparatus useful in breaking dogs from barking, incorporating a microphone, threshold detecting circuit which senses a bark or other noise from the dog of suitable amplitude and duration, an oscillator providing an output frequency sufficiently high that human ears cannot hear it, a mixer circuit where the oscillator frequency is modulated by the bark, and a filter circuit which rejects low frequency components of the mixed signal to avoid annoying humans, and a power output amplifier connected to a speaker. The threshold detector controls the application of power to the output amplifier. When the device operates, the dog''s bark modulates the higher frequency tone which is annoying to the dog, and the dog soon learns that the barking is punished by the high frequency sound. The silence of the dog is rewarded by termination of the high frequency sound. A switch override provides continuous output of tone.

Sound pressure distribution in the outer ear.

Abstract: Sound pressure transformation between several points in the outer ear and the eardrum was measured by means of a probe-tube microphone. The tip of the probe tube was positioned with the help of a fine screw arrangement and a Zeiss surgical microscope. The results slightly amend and extend the classical data of Wiener and Ross.

Parabolic sound reflecting microphone holder

Abstract: A parabolic sound reflecting microphone holder is disclosed made of a transparent plastics material about 18 inches in diameter and from 0.080 to 0.125 inches thick having good acoustic properties in the low frequency range of from about 150 to 500 cycles per second.

Electronic tuning device for musical instruments

Abstract: A miniaturized electronic device for tuning musical instruments includes a pick-up microphone and an array of light emitting diodes. A phase lock loop connected to the microphone locks to the fundamental, a harmonic or subharmonic of the tone produced by a musical instrument and produces a corresponding output. A tone reference generator and associated frequency selector produce a reference output at a frequency n times that of the fundamental of the correct tone, there being n display diodes in the array. A sequencing device connects the two outputs to the display diodes so that when the tone is sharp the diodes are sequentially energized in one direction and are sequentially energized in the opposite direction when the tone is flat. When the tone produced by the musical instrument is in pitch, a stationary display is produced by periodic energization of only one of the diodes.

Handsfree loudspeaking key telephone set and a switching circuit for use in a microphone and loudspeaker equipped key telephone

Abstract: A key telephone system is disclosed comprising microphone and loudspeaker equipped key telephone sets in which intercom calls are received through the microphone and loudspeaker. Additionally, the microphone and speakers may be used for central office calls. When so used, brief intercom calls can be allowed to break in, automatically placing the central office call on hold.

Capacitance microphone static membrane deflections: Comments and further results

Abstract: The biasing of capacitance microphones by a constant voltage or electret charges places electrostatic forces on the microphone’s membrane diaphragm. Due to the dependence of the electrostatic forces on the deflections, the final membrane position is governed by a nonlinear differential equation. Because of this nonlinearity, certain ranges of the parameter values exist for which stable static deflections cannot be obtained. Numerical methods are usually used to obtain the deflections and their critical or highest stable values. The results of two past investigations using different forms for the nondinemsionalized nonlinear differential equation are reviewed and compared [Warren et al., J. Acoust. Soc. Am. 52, 711–719 (1972); Friam et al., J. Acoust. Soc. Am. 53, 1601–1608 (1973)]. A third, and perhaps more appropriate, form for the nondimensionalized differential equation is presented and discussed. Using this third form, deflection and stability results are reviewed for circular and annular membranes. R...

Portable television camera with audio communication

Abstract: A portable television camera wherein a first housing carries a picture taking lens and a loudspeaker which is connected to the control center, and a second housing carries a view finder and a microphone for communication with the control center. The two housings are adjustably connected to each other by a hollow coupling which surrounds electrical conductors connecting the microphone and the view finder with parts in the first housing.

Sound signal changing circuit

Abstract: A sound signal changing circuit in which a sound signal component such as singing voice or the like contained in a signal reproduced from a pre-recorded tape, a record or the like is attenuated or removed and a sound signal from a microphone is inserted in the first-mentioned signal in place of the attenuated or removed signal component.

Device for early detection of rupture of the pressure part of a boiler

Abstract: A device for early detecting any abnormal conditions of a boiler from the sound wave which is generated when water or steam spouts from the pressure part of the boiler. The device is adapted for use in an atmosphere, such as a recovery boiler, which is liable to contamination, and comprises a gate circuit for shutting a sound wave transmission tube and shutting an output of a microphone upon actuation of soot blowers of the boiler so as to protect the device against detrimental effects imposed thereon by the operation of the soot blowers, means for cleaning the transmission tube by passing pressurized air therein while the output of the microphone is being shut down, means for cooling the sound wave transmission tube, means for detecting an abnormal condition of the microphone by passing pressurized air in the vicinity of said microphone and means for detecting clogging of the sound wave transmission tube by pressure.

Noise pollution level measuring circuit

Abstract: Noise pollution level (NPL) is measured by a circuit according to the formula NPL equals Le plus 2.5 sigma where Le is the mean sound pressure level and sigma is the standard deviation of the sound pressure level, both quantities being taken over a fixed time interval. The circuit includes a microphone, a circuit connected thereto for providing a sound pressure level, a circuit for integrating the sound pressure level through the fixed time interval to provide the mean sound pressure level, a standard deviation circuit responsive to the sound pressure level signal to determine the standard deviation over the fixed time interval, sample and hold circuits to store the Le and sigma signals after the fixed timing interval, a timing circuit to control the time intervals and a circuit for adding the Le and sigma signals to produce the NPL output.

Microphone with different directional modes

Abstract: A built-in microphone for a tape recorder, comprising a diaphragm responsive to sound waves and sensing means behind it in the microphone case. The microphone case has at least one opening to admit the sound waves to impinge on the inner surface of the diaphragm so as to counteract the effect of the sound waves impinging on the outer surface of the diaphragm for unidirectional mode of operation. The openings can be closed for nondirectional mode of operation.

Signal processing circuit

Abstract: In sound target detection equipment, at least three microphones are used in a broadside array manner to ascertain the presence of a selected sound source. The outputs of the three microphones all include the sought signal S and respectively contain noise components X, U and Y. These outputs are combined to provide X-U and X-Y. These two signals are then applied as separate inputs to a discriminator which applies the rules: (a) when the input signals are both of the same polarity, the discriminator selects the input closer to zero and presents it as the output; (b) when the input signals are of opposite polarity, the device presents zero as the output. The output from the discriminator is then subtracted from one of the original microphone outputs in a manner tending to cancel out the noise contents, and the resulting signal examined for the presence of the sought signal S. The invention is applicable also to non-aural signal detection equipment.

Sound communication system

Abstract: A communication system for an emergency vehicle including a provision for selectively producing plural automatically and manually controlled siren sounds, the sound broadcast of radio reception and the sound amplification of the input to a microphone. A complete momentary-contact, pushbutton console may be employed, if desired, by short circuiting all the inputs to ground except that corresponding to the mode of operation selected. Start up instability is also eliminated. A selector pushbutton performs the dual function of manual siren control. Negative feedback from the speaker is provided selectively for radio and public address system use. Common use of components reduces cost and complexity. For example, common use of a voltage controlled oscillator, two amplifier stages, a driver and a speaker assembly is made. Radio input is turned on by an alternate action switch. As described in the specification, the action of ''''turning on'''' the radio shorts out all siren functions by firing silicon controlled rectifiers. The microphone input is turned on by pushing the ''''push to talk'''' switch thereon. This action fires all the siren shorting silicon controlled rectifiers through a pulse amplifier.

Radio transmission system

Abstract: A radio transmission system for use by the operator of a motorcycle or other vehicle subject to high background noise, comprising a helmet worn by the operator and carrying a small low powered transmitter including a microphone located adjacent the operator''s mouth at all times. A small receiver carried by the motorcycle is tuned to the frequency of the transmitter and its output is connected by a wire conductor to the input of a relatively high powered transmitter carried by the motorcycle and operating on a different frequency.

Detection of acoustic sources using long‐wavelength acoustical holography

Abstract: Sound sources from vibrating circular and ribbed rectangular plates are detected by holographic means using a microphone scanner and associated photographic equipment. Reconstruction of the wavefront from the acquired acoustical holograms reveals the areas on the plates which generate the far‐field acoustic radiation. In all cases, the plates were driven below their coincidence frequency. The location of the sound sources on the plates supports the theory of acoustic radiation from complex vibrators except for irregularities which are due to inhomogeneities of the plate material, nonlinearities of the holographic technique, and the speckle effect.

Silent emergency alarm system for schools and the like

Abstract: An emergency alert system is described. In a school each classroom (or other area) is instrumented with a hidden microphone and receiver tuned to a non-audible frequency. The receivers' outputs are connected to a central display unit in the school's administrative office. Each instructor is provided with a small concealable transmitter which, when hand activated by the instructor upon the occurrance of any emergency, generates a non-audible signal at the receiver's tuned frequency.

Camera and microphone combination having a variable directional characteristic in accordance with a zoom lens control

Abstract: A simultaneous picture and sound recording system provides variation of the directional characteristic of a sound-receiving microphone in accordance with the zoom lens adjustment of a motion picture camera. The motion picture camera having a zoom lens is provided with a potentiometer which is interlocked with a zoom control ring capable, upon rotation, of moving the zoom lens assembly along the optical axis to derive a difference signal which is fed to an electric circuit device incorporated in the system. The electric circuit device is connected to a microphone having a variable directional characteristic so that the output signal from the device is directed to the input of the microphone. The combination makes it possible to increase the directional response characteristic of the microphone in the main direction, while adjusting the focal length of the motion picture camera from the wide angle setting to the telephoto setting.

Microphone and connector unit therefor

Abstract: An electret microphone provided with a protruding pin shaped terminal member which is adapted to pierce the tie or other clothing of the user and engage a connector unit located behind the clothing of the user. The connector unit is electrically connected to a power unit supported remotely on the user.

CB microphone-AM/FM radio control with AM-FM radio cut off switch and microphone holder

Abstract: A microphone holder having a slot for receiving the headed shank of a microphone, and a switch located for operative engagement by the shank head to electrically close the switch, so that the switch connected in an AM/FM radio will automatically disable the latter upon use of the CB radio, and return the AM/FM radio to operation upon replacement of the CB microphone in the holder.

Floor wave microphone stand

Abstract: A microphone stand for responding to the floor wave of a distant acoustical source which utilizes a body of open cellular foam plastic having between 10 and 80 voids per linear inch and having a total volume of voids of at least 90 percent of the total volume of the body. The body has a flat side which permits it to be placed upon a horizontal surface such as a floor and a cavity therein to snugly accommodate a microphone and hold it in position.

Hearing aid with directional microphone - has device converting microphone lobe characteristic into spherical characteristic

Abstract: The aid has a sound entry orifice facing forward. A switch is connected to the above switching device, controlling means determining the amplifier, frequency characteristic. The switch controls any one of the following: connects attenuators for lower frequencies; or an additional amplifier channel; or an additional treble boost at its position for directional reception, or connects additional electrical and/or acoustical filters or resonators, or it changes the hearing aid dynamic range as required. The aid avoids the sudden strengthening of the lower frequencies which usually happens on the closing of the second sound channel. An optimum reproduction over the complete audio range by means of a single apparatus is the chief object of the aid.

Telephone transmitter circuit

Abstract: A microphone, for example an electret microphone, may be combined with an amplifier to replace a typical carbon telephone transmitter. Such a combination is modified by the addition of a controlled impedance a-c shunt load circuit between the self polarized transmitter and a typical loop circuit. The shunt load circuit co-acts with the output impedance of the amplifier to simulate the conversion efficiency of the typical carbon microphone over a range of loop circuit operating voltages.