Showing papers on "Microphone published in 1968"

Broadband Matching of Resonant Circuits and Circulators

Abstract: In a high-power microwave system (particularly a CW or long-pulse system), it often becomes necessary to protect the transmitter from the damaging effects of RF breakdown in the waveguide. The onset of RF breakdown may be detected by optical detectors or by an increase in the reflected RF signal. Fast switches can be arranged to turn off the transmitter in a time of the order of a microsecond. Under these conditions, it becomes difficult to determine the location of the breakdown. This correspondence describes an experiment to test the feasibility of locating the arc by measuring the time delay required for the sound from the arc to reach a microphone placed at some point in the waveguide.

Headset incorporating a microphone and an earphone

Abstract: A DYNAMIC MICROPHONE TRANSDUCER AND AN EARPHONE TRANSDUCER ARE MOUNTED IN FRONT AND REAR HALF-SHELLS WHICH FIT TOGETHER TO FORM A CASING. SOUND IS BROUGHT TO THE MICROPHONE TRANSDUCER BY A VOICE TUBE EXTENDING FORWARDLY FROM THE FRONT HALF-SHELL. AN EAR TUBE IS CONNECTED TO THE REAR HALF-SHELL TO CARRY THE SOUND FROM THE EARPHONE TRANSDUCER TO THE EAR OF THE USER. POROUS DISCS MADE OF SINTERED METAL ARE PREFERABLY MOUNTED IN THE TUBES FOR DAMPING RESONANCES THEREIN. THE HEADSET IS SUPPORTED BY A MOUNTING MEMBER HAVING FRONT AND REAR CLIPS OF GENERALLY CIRCULAR CURVATURE FOR RESILIENTLY ENGAGING THE HALF-SHELLS TO HOLD THEM TOGETHER. THE HALF-SHELLS ARE PREFERABLY FORMED WITH RECESSES FOR RECEIVING THE CLIPS IN SUBSTANTIALLY FLUSH RELATION TO THE HALF-SHELLS. THE MOUNTING MEMBER PREFERABLY INCLUDES A TEMPLE CLIP FOR MOUNTING THE HEADSET ON ONE OF THE TEMPLES OF A PAIR OF EYEGLASSES. A SWIVEL JOINT IS PREFERABLY PROVIDED BETWEEN THE TEMPLE CLIP AND THE FRONT AND REAR CLIPS.

Antistuttering therapeutic device

Abstract: A therapeutic device which provides voice masking to assist a patient in overcoming a speech deficiency such as stuttering. A microphone, selectively responsive to the patient''s voice, receives his speech and converts it into electrical signals which are utilized to develop a control signal. An audio oscillator generates an audiofrequency pulsed wave which is varied in frequency in proportion to pitch changes in the patient''s voice by a circuit responsive to the control signal. An output transducer converts the audiofrequency pulsed wave into a corresponding sound wave which is applied to the patient''s ear. A switching circuit, also responsive to the control signal, enables application of the sound wave only while the patient is speaking or attempting to speak.

Microphone and headset for underwater swimmer

Abstract: An improved headset and microphone construction for use in aqueous environments of high ambient pressure and a method of manufacture thereof.

“N Waves” from Bursting Balloons

Abstract: When a round balloon is burst “perfectly,” the resulting acoustic disturbance should have the shape of the letter N. In the experiments reported here, the N wave is received by a baffled microphone, whose frequency-response characteristic is flat to about 80 kHz. The oscillogram of the microphone output is then photographed. The waveforms obtained show deviations from the idealized N shape, which are attributed to loss of spherical symmetry. Important factors determining the departure from spherical symmetry are the type of balloon and the method of bursting. By paying careful attention to experimental technique and photographing the waveforms from many balloons, it is possible to obtain good approximations of the N shape.

Loudspeaker telephone circuit arrangement

Abstract: A LOUDSPEAKER TELEPHONE CIRCUIT ARRANGEMENT PROVIDING A HYBRID CIRCUIT COUPLED TO A TELEPHONE LINE, A MICROPHONE TRANSMISSION CHANNEL AND A LOUDSPEAKER RECEPTION CHANNEL COUPLED TO AN INPUT AND AN OUTPUT OF THE HYBRID CIRCUIT RESPECTIVELY, A CONTROL CIRCUIT COUPLED TO THE MICROPHONE CHANNEL AND THE LOUDSPEAKER CHANNEL FOR CONTROLLING THE TRANSMISSION TO AND RECEPTION FROM SAID TELEPHONE LINE RESPECTIVELY, A MICROPHONE SWITCHING AMPLIFIER AND A LOUDSPEAKER SWITCHING AMPLIFIER COUPLED BETWEEN THE CONTROL CIRCUIT AND THE MICROPHONE CHANNL AND BETWEEN THE CONTROL CIRCUIT AND THE LOUDSPEAKER CHANNEL RESPECTIVELY FOR BIASING THE CONTROL CIRCUIT IN OPPOSITE DIRECTIONS, AN ECHO DETECTOR COUPLED BETWEEN THE LOUDSPEAKER CHANNEL AND THE MICROPHONE SWITCHING AMPLIFIER TO PREVENT LOUDSPEAKER SIGNALS FROM BEING TRANSMITTED OUT ON THE TELEPHONE LINE, AND A BREAKTHROUGH MUTING CIRCUIT COUPLED BETWEEN THE HYBRID CIRCUIT AND THE LOUDSPEAKER SWITCHING AMPLIFIER TO PREVENT "BREAKTHROUGH" OF SIGNALS FROM SAID MICROPHONE CHANNEL TO THE LOUDSPEAKER CHANNEL VIA THE HYBRID CIRCUIT.

Acoustical-electrical transducer and support assembly

Abstract: An acoustical-electrical transducer and support assembly is composed of an elongated tubular member which supports a microphone capsule of a condenser microphone at one end and the preamplifier of the microphone at the other end with electrical circuitry extending through the tubular member connecting the capsule and the preamplifier. A counterweight member is movably positionable on the end of the tubular member opposite the microphone capsule and incorporates the preamplifier. The tubular member and its attached parts are pivotally supported on a support member at the center of gravity of the assembly. In this arrangement the microphone capsule can be selectively positioned about the support member with its preamplifier disposed in a spaced nonobstructing location on the tubular member.

Cordless,self-contained microphone transmitter

Abstract: A CORDLESS, SELF-CONTAINED, FREQUENCY MODULATED MICROPHONE TRANSMITTER INCLUDING A HOUSING ADAPTED TO BE HAND-HELD, A MICROPHONE PICKUP ELEMENT, AND A CIRCUIT COMPRISING A BATTERY, AN INPUT IMPEDANCE MATCHING AND EQUALIZATION NETWORK, A TRIPLEX COLPITTS RADIO FREQUENCY OSCILLATOR-MODULATOR, AN ANTENNA THAT INCLUDES COMPONENTS OF THE MICROPHONE PICKUP ELEMENT, AND AN ISOLATING BUFFER AMPLIFIER TO COUPLE FREQUENCY MODULATED ENERGY TO THE ANTENNA.

Cosmic dust sensor

Abstract: A sensor for detecting and measuring the energy, velocity and direction of travel of a cosmic dust particle, comprises an array of electrodes. Some of the electrodes are arranged in columns and spaced in close proximity to other electrodes that are disposed in rows. Together the columns and rows define a plurality of sectors through which a cosmic particle may traverse. Each electrode includes electrically biased conductor layers supported on an optically transparent matrix. Ions and electrons from an impacting cosmic dust particle compose an ionized plasma for collection on the electrically biased conductors, creating an electrical output pulse which may be amplified. A second array of electrodes in columns and grids in rows is included in spaced relationship from the first array. An impacting cosmic dust particle on the second array produces an electrical output pulse in the same manner as described. Should a particle penetrate the first array and impact upon the second spaced array, a pair of time spaced electrical outputs will result, the time spacing of the pulses being proportional to the velocity of the particle. The direction of the particle''s travel, and thereby its origin in space is determined by the alignment of respective sectors traversed by the particle. Behind the second array is placed a microphone plate which arrests further penetration of the particle. The microphone output amplitude is an indication of the momentum of a particle. At least one of the secottors in each of the arrays is bounded by an epoxy coating rendering it impervious to plasma collection. Accordingly, a pulse output originated from the impervious sector gives an indication of noise or other interference collected by the sensor. Additionally, a second microphone of small area is segregated from the first-described microphone and is provided with a separate output. Accordingly, electrical signals from the small microphone which are disproportionate with respect to the small area of the second microphone are indicative of interfering noise as well as particle impact.

Calibration of Standard Condenser Microphones: Coupler versus Electrostatic Actuator

Abstract: The response frequency characteristics of a “1‐in.” condenser microphone measured by an electrostatic actuator is likely to be significantly different from that measured by reciprocity in an acoustic coupler because of the radiation impedance of the microphone diaphragm with the actuator in place. It cannot be assumed, except at low frequencies, that the radiation impedance is negligible and that the actuator calibration yields the pressure response. Such an assumption also is apt to lead to errors in the determination of the free field response when calculated with the aid of the free‐field correction.

Labyrinth for unidirectional microphone

Abstract: A labyrinth structure for a unidirectional ribbon-type microphone comprises an outer shell-like member and at least one inner member, each having open and closed ends, the space enclosed by the outer member being divided into at least two communicating chambers by the inner member. The inner chamber, in addition to being the end of the labyrinth path, can be used to house microphone components therein and also to shield these components by making at least one member of a good electrical conductor.

Sound reflecting telephone casing

Abstract: A telephone instrument in which either the microphone or the receiver transducer is used in the ''''on-hook'''' condition to emit tone calling signals. The instrument casing is shaped to provide recesses for the microphone and receiver housings such as to define, with the housing of the tone-emitting transducer, a cavity which provides acoustic enhancement of the emitted tone. The transistor amplifier within the casing is connected to act as an oscillator to generate the calling tone in the ''''on-hook'''' condition and as a speech current amplifier in the ''''off-hook'''' condition.

Problems of diver communication

Abstract: The major problems of underwater communication are microphone and earphone construction speech distortion caused by high pressure and/or mixed gas breathing environments, and face mask design. Microphone and earphone elements have recently been developed that are relatively unaffected by increased ambient pressure. These elements are constructed of piezoelectric ceramics encased in a unique rubber housing to prevent water leakage. Preliminary tests indicate that the frequency response of these elements is changed less than 3 dB by pressures exceeding 500 lbf/in2gauge. Extensive research in speech distortion under extreme pressures with various gas mixtures includes voice spectrum analysis, study of adaptation changes in speech, and intelligibility measurements of helium speech before and after processing or "unscrambling." These basic data provide information for the design of microphones, masks, and electronic and mechanical means of normalizing distorted speech. Face mask design must include consideration of breathing requirements, as well as speaking requirements. The design of a speaking cavity has, of necessity, been based on empirical data. These designs often conflict with the primary requisite of proper breathing design. Electronic compensation is often employed to correct or improve deficiencies in mask characteristics.

Sound transmission measurement

Abstract: 1,117,723. Sound transmission measurement. FORD MOTOR CO. Ltd. 27 Jan., 1967, No. 4124/67. Heading H4D. In a system for measuring the sound absorption properties of a sample 14, the sample is mounted in an opening between a reverberant chamber 11, containing a sound source 31 and a microphone 32, and a chamber 12 containing a microphone 33 and having an anechoic wall portion and a reflective wall portion, means being provided for measuring the sound levels sensed by the two microphones and hence indicating absorption. The chamber walls provide sound insulation from external noise. Chamber 11 is fitted with reflecting liners 18 arranged at irregular angles to eliminate standing waves, and the anechoic wall portion of chamber 12 comprises absorbent wedges 24. The wall materials and shape in chamber 12 are such that any sound energy reflected inside chamber 12 is absorbed before it reaches microphone 33. Transmission loss through sample 14 is determined as a function of sound frequency by driving source 31 from a bandpass filtered (one third octave) random noise generator and recording the two microphone outputs, the microphone outputs being sampled alternately.

Comment on paper by Bhartendu, "A study of atmospheric pressure variations from lightning discharges"

Abstract: Bhartendu uses two types of microphones to provide the time series for his power spectral investigations of thunder, the hot wire microphone and a wide-range crystal microphone with amplification provided by a sound-level meter. He then takes power spectra calculated from these time series and states conclusions regarding the power spectrum of thunder. Data and discussion are presented here to demonstrate that one cannot use a single-grid hot-wire microphone for power spectral analysis without introducing spurious spectral components.

Alarm system sensitive to cut cables and insensitive to r-f interference

Abstract: IN AN ALARM SYSTEM WITH A BALANCED SHIELDED MICROPHONE CABLE A BARE DRAIN WIRE IS TIED TO THE CABLE SHIELD AT THE END OF THE MICRPHONE CABLE, THE END MICROPHONE BEING TERMINATED WITH RESISTORS SO THAT CABLE CUT BRIDGE CIRCUIT DETECTS AN UNBALANCE WHEN ANY MICROPHONE CABLE IS CUT TO PROVIDE AN ALARM SIGNAL AND REDUCE R-F INTERFERENCE.

Indirect measurement of arterial blood pressure with the aid of a digital computer

Abstract: Indirect measurement of arterial pressure was carried out using a cuff and a microphone positioned over the brachial artery. Selective sound sampling, data analysis, and remote control of the arm cuff pressure were used. Criteria for “acceptability” of Korotkoff sounds were developed. Sampling of the microphone signal was done at cuff pressures where an acceptable sound was expected. Data obtained in 15 postoperative cardiac patients with this method and with a direct method were compared. Indirect systolic measurements averaged 11 mm. Hg lower than direct measurements. Diastolic averages for direct and indirect pressures were equal.

Improvements in and relating to microphones

Abstract: 1,136,794. Microphones. COSMOCORD Ltd. 5 July, 1967 [5 July, 1966], No. 30062/66. Heading H4J. A microphone comprises a casing having a body 10 and a cover 19 mounted by pivots 16, 17 on the body 10. A microphone transducer (14), Fig. 2 (not shown), is mounted in the body 10. The cover 19 is movable between a first position in which it obstructs or modifies sound apertures 13 against the ingress of sound (Fig. 4) and a second position in which it serves merely as a support member for the microphone. Thus in the second position the cover 19 may be completely open and in line with the body 10 to act as a handle (Fig. 1). Alternatively, in the second position the cover 19 may be at an angle to the body 10 and act as a rest for supporting the microphone on a flat surface (Fig. 3, not shown). In the first position the cover 19 is folded to lie closely against the back of the body 10. If a cardioid transducer is used, closure of the back changes the polar diagram to omnidirectional. Closure of the apertures 13 may be improved by using a foamed polyurethane pad 20. The back of the body 10 may carry an acoustic filter to modify the acoustic effect due to the rear slots. A decorative fret (15), Figs. 2, 3 (not shown) of perforated plastics or expanded metal may fit over the front of the body 10.

Dictating machine with microphone operated cradle switch

Abstract: The invention relates to a combined dictation machine and detachable microphone cradle. The bottom of the dictation machine has a pair of sockets, one being electrically connected to the power circuit and the other being closed by a leaf switch element completing the circuit. The microphone cradle includes a pair of projecting pins connected to a microphone-operated normally closed switch. Upon insertion of the pins of the microphone cradle into the sockets of the dictation machine the leaf switch breaks the power circuit within the dictation machine and completes the circuit through the normally closed switch in the cradle so that control over the power circuit of the dictation machine is transferred to the microphone-operated cradle switch.

Design and Measurement of Infrasonic Gradient Microphones and Windscreens

Abstract: Until recently, infrasonic phenomena have been explored mainly with pressure microphones. Gradient microphones, especially when arranged in an orthogonal bigradient array, have the capability of providing information about the direction, as well as the intensity and time of sound arrival. A low‐frequency bigradient array is described. An equivalent circuit for analyzing infrasonic gradient microphones is developed and applied to the analysis of errors that may be expected when the microphone is measured in a spherical field. A plane‐wave calibrator for infrasonic gradient microphones and windscreens, with internal dimensions of 4×4×8 ft, has been built along the principles of the laboratory calibrator for gradient hydrophones described by the present author [J. Acoust. Soc. Amer. 39, 585–586 (1966)] with the added capability for testing the acoustical symmetry of infrasonic microphones. Windscreens affect the low‐frequency response of gradient microphones and the new equivalent circuit has been applied to...

Sound recording apparatus

Abstract: 1,120,720. Pulse modulation circuits. EASTMAN KODAK CO. 21 April, 1967 [25 April, 1966], No. 18455/67. Heading H4L. [Also in Division G5] In a sound recording system (see Division G4-G6), a light emitting diode 16 emits light pulses in response to output pulses from an oscillatory circuit including a unijunction transistor 21, the pulse repetition frequency being varied by variation in the capacitance of a crystal microphone 35 in accordance with an audio input signal. The output pulses from the unijunction transistor 21 are amplified by a coupling transistor 45.

Improvements in or relating to audio frequency amplifier systems

Abstract: 1,137,448. Microphone circuits; automatic volume control. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 24 Aug., 1967, No. 38994/67. Headings H4J and H4R. In an audio amplifier system of the fixed frequency pilot tone A.G.C. type the fixed frequency tone is of ultrasonic frequency and is injected acoustically. The system is for use with an ultrasonic pilot tone generator and transducer carried by a performer, e.g. on a lapel, spectacles, tie-pin or hung round the neck. By such arrangement movements of the performer, which cause variations in input volume, cause little variation in output volume. A loud-speaker S (Fig. 1) is fed by an amplifier A which amplifies both audio signals and ultrasonic pilot signals. A filter F separates the pilot signals which are utilized to provide A.G.C. (e.g. by rectification) to control the amplifier gain. A single microphone M receives both sound and ultrasonic waves. The sound source P of the performer has polar diagram p and the pilot transducer T has a polar diagram t. The transducer T is more directional than the performer but this does not matter at low ultrasonic frequencies (e.g. 20 to 25 kc/s.) if major movements are relied upon. With a higher ultrasonic frequency the polar diagram t may be widened, e.g. by using two or more transducers in parallel. Alternatively a microphone (M1), Fig. 2 (not shown) receives sound waves while a microphone (M2) receives the ultrasonic waves, the outputs from the microphones (M1, M2) being applied to the amplifier (A) by a mixer (C1). In another arrangement the ultrasonic microphone (M2), Fig. 3 (not shown) is coupled directly to the A.G.C. device which controls the amplifier (A), there being no feed-back type A.G.C. loop.

Voice-controlled actuator

Abstract: 1,101,420. Controlling and actuating by sound. INSTITUTE FOR SCIENTIFIC INFORMATION. 22 Dec., 1964, No. 52088/64. Heading G4F. [Also in Division E1] A voice-controlled actuator comprises a first sensing system 22 including an audio spectral analysing device 30 coded to yield an output signal in response to a signal including specific spectrum of audio frequencies by comparison of a received signal with a record of the audio spectral characteristics of a specific command signal in the form of sound uttered by a specific individual; a second and similar sensing system 23 coded to respond to any received signal other than the said command signal to inhibit an output signal from the device of said first sensing system; and means for applying a received voice signal to the sensing systems. In the construction shown, the transducer is a microphone 24 and this is connected to an electromechanical driver 58 of the analyzing device. The analyzing device comprises in addition, a fibre optic array 60 which comprises a large number of tiny quartz fibres 64, all held at one end by an inclined or otherwise contoured base 62 so that all the fibres 64 are of different lengths so that, since each is a tiny cantilever beam, each will vibrate at a different frequency whenever it is mechanically excited at its natural frequency. Each fibre has sufficient space around it to vibrate in any direction without striking any other fibre. The analyzer also includes an incandescent lamp 36 and a diffuser 54 which are placed in a light sealed housing 56 on top of the electromechanical driver 58 so that the light from the lamp can pass through the fibre optic array 60. The electromechanical driver 58 shakes the fibre optic array in response to an audio signal received by the microphone and to sense the pattern of fibre motion, a mask is imposed between the fibre optic array and a photo-cell 66. The mask 52 is made by placing a photographic plate between the fibre optic array and the photo-cell and vibration of the array by a specific audio signal will cause each fibre that vibrates to leave a black line on the negative developed from the photographic plate and each which does not vibrate to leave a black spot; elsewhere the plate will be transparent. A positive is produced from the negative and this is used as the mask in conjunction with a negative formed by placing a photographic plate between the mask and the photo-cell and illuminating the array when the array is not vibrated; this produces an array of small spots on the photographic plate when developed, corresponding to the number of fibres. A mask produced from the positive and negative formed in this way will only pass light from the fibres which move in response to the specific audio signal used in producing the positive plate and this falls on the photo-cell and is used to actuate a time delay relay 74 via a Zener diode which only allows the relay to operate when the intensity of light on the photo-cell exceeds a specific amount. The contacts 46 of the relay complete the circuit to a control device 42 for a servomotor which, as described, withdraws a latch bolt to unfasten a door. To prevent a blast of sound which contains the frequencies of the specific audio signal operating the control device 42 the second sensing system is connected in parallel with the first to the microphone and in this system the negative photographic plate produced by the specific audio signal is used as the mask between the fibre optic array 60 and the photo-cell. This sensing system responds to all frequencies other than those of the specific audio signal and the relay controlled by the photo-cell opens a contact in the circuit of the control device 42 when such additional frequencies are present in the signal received by the microphone. When the mechanism is used as a lock mechanism for a door to withdraw a bolt, a switch is provided in a knob on the door which must be pressed to provide power to the mechanism. If it is desired that two separate command signals can operate the servomotor, two additional sensing systems as above are provided connected to a common microphone and controlling the servomotor, the relay contacts being arranged in parallel with those of the first pair of sensing systems. An arrangement is also described by which two separate command signals are required to operate the servomotor.