Abstract: A method wherein an auralization is performed, in that a plurality of spatial pulse responses are incited from various locations in the same room, and are received via a multi-channel receiving apparatus, for example, a directional microphone or a plurality of directional microphones at one location, and are recorded. For the reproduction, a multi-channel loudspeaker arrangement of vertically configured loudspeakers and of horizontally configured loudspeakers is used, at least two loudspeakers being required to reproduce sources in one line from point to point that are able to be localized, at least three loudspeakers for reproduction in one plane, and at least four loudspeakers in one room.

Abstract: A stereo headphone employing a standard stereo headphone plug is adapted for automatically hearing a monaural signal at both earpieces, when accessing a typical monaural source. In the first embodiment of the invention, an impedance element couples the signal from a first acoustical driver that receives the monaural signal from the stereo plug tip, to a second acoustical driver that is connected to the stereo plug ring and normally receives no signal when plugged into a conventional monaural audio source output jack. The magnitude of the coupling impedance is selected with respect to the impedance of the acoustical driver so that the reduction in loudness at the second earpiece due to the signal voltage drop across the coupling impedance is not perceptible to the listener. This will occur when the reduction in loudness at the second earpiece is less than the threshold of perceivable loudness reduction at one ear when there is no reduction in loudness at the other ear.

Abstract: An apparatus and method for providing controlled acoustic isolation within various forms of headsets. The invention provides manual and automatic mechanisms for changing the amount of acoustic isolation provided by the headsets. Sounds in the environment that the user wishes to be made aware of can be programmed into a set of stored sound selection characteristics. In response to correlation of the stored sound characteristics with sounds in the external environment the headset decreases acoustic isolation by coupling signals from one or more external microphones to the audio conversion elements within the earpieces. Alternatively, the apparatus can respond to sounds to be blocked by increasing acoustic isolation. A manual control may be activated by the user to decrease acoustic isolation at their discretion.

Abstract: A sound system and method for modeling a sound field generated by a sound source and creating a sound event based on the modeled sound field is disclosed. The system and method captures a sound field over an enclosing surface, models the sound field and enables reproduction of the modeled sound field. Explosion type acoustical radiation may be used. Further, the reproduced sound field may be modeled and compared to the original sound field model.

Abstract: The problem addressed by the invention, to develop a microphone with assoted amplifier which has a better dynamic response than analog microphones, requires less space, can replace analog microphones by using cables already in place, and has a low-cost construction, is solved by the invention in that the microphone is made up of an electroacoustic transducer, two analog-digital converters, two preamplifiers connected to the output of the electroacoustic transducers on the one hand and on the other hand each with preamplifiers connected each to an analog-digital converter, and with a driver stage connected to the analog-digital converters for a two-channel digital audio format and in that the amplifier is made up of a receiver for a two-channel digital audio format and a signal processor which generates a one-channel signal from the two-channel audio format as an image of the signal of the electroacoustic transducer. The field of application is in musical production. The invention is illustrated by FIGS.

Abstract: Method of controlling sound is performed in a computer monitor having sound processing function, and comprises the step of modifying a volume limit value, i.e., a maximum sound volume value adaptive to the incorporated software and/or hardware of the personal computer so as not to generate howling in the monitor. The method is accomplished by a microcomputer. With the method, when a volume limit level modifying signal to modify the volume limit value is externally applied, the microcomputer neglects a previously set volume limit value and stores a new volume limit value which is adjusted by an operator.

Abstract: In a method for constructing an acoustic transfer function table for virtual sound localization, acoustic transfer functions are measured at both ears for a large number of subjects for each sound source position and subjected to principal components analysis, and that one of the transfer functions which corresponds to a weighting vector closest to the centroid of weighting vectors obtained for each sound source position and each ear are determined as a representative.

Abstract: An audio processing system applies a filter to convert the audio signals generated by the microphone of a combined microphone/speaker earpiece into filtered audio signals, where the filter is designed to correct for distortions in the audio signals that result from the microphone being part of the combined earpiece.

Abstract: A method of synthesizing a set of filters comprises locating first and second loudspeakers at first and second locations, respectively, coupling a first component of an audio program to the first loudspeaker to be reproduced thereby, and coupling a second component of the audio program to the second loudspeaker to be reproduced thereby. First and second microphones are placed at third and fourth locations, respectively, at which the reproduced first and second audio components are to be heard in order to convert audio impinging upon the first and second microphones into first and second microphone signals, respectively. A first set of transfer functions is developed from the first and second components of the audio program and the first and second microphone signals. One loudspeaker is then located at a fifth location different from one of the first and second locations. The first component is then coupled to the first loudspeaker, and the second component to the second loudspeaker.

Abstract: An audio processing system is used to process digital audio signals that represent sound emanating from a source that is moving through three dimensional space. The audio processing system has a filter unit that employs infinite impulse response (IIR) filters to filter the audio signals. The IIR filters have filter coefficients that change when the sound source is stationary or moves from one location to the next in the 3D space. To minimize the transient response following a coefficient change, the filter unit initializes elements in the tap delay lines of the IIR filters to non-zero values. In one implementation, the tap delay line elements are changed to a set of predetermined non-zero values. In another implementation, the tap delay line elements are initialized to the final values produced by the filter for the previous sound source location.

Abstract: A device and method are disclosed which perform diagnostics on a microphone and display diagnostic information and instructions to a user. The invention uses a processor to create histograms of the PCM (Pulse Code Modulation) signal after removing any dc bias to determine signal and noise levels and ratios, as well as other parameters. Messages are generated and displayed by the device and method to inform a user that the microphone is working correctly or about possible malfunctions, such as low gain. The messages can advise the user on steps to take to correct the malfunctions, for example, to try a different adapter cable or plug.

Abstract: A transportable sound reproduction system for transducing binaurally encoded signals with near-field reproduction including a support, a head locator attached to the support for positioning a listener's head at a desired location in the near-field, and a pair of speakers located close to and forward of the desired location of the listener's head. A carrying case for transporting the system has protective packaging with compartments for detachably securing the components of the system.

Abstract: A sound capturing method and device for use in making recordings having improved three-dimensional imagery during playback. Vibration information is detected from a body portion through the use of a crystal microphone for generating a first signal corresponding to a vibrational frequency of the body portion in response to a received sound wave. Direct sound information is detected from the body portion through the use of a condenser microphone affixed thereto at a second location for generating a second signal corresponding to a frequency of the received sound wave. The first and second locations are in proximity to one another such that a sound wave will reach each location at substantially the same time. Alternatively, the signals received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time.

Abstract: A microphone system includes a portable frame for mounting linear pick-up microphones such that each of the microphones has its diaphragm facing outwards from the frame and the diaphragms form a generally elliptical pattern. A microphone with a substantially hemispherical pick-up pattern is mounted on the frame such that it is directed upwards and a second substantially hemispherical pick-up pattern microphone is mounted on the frame directed downwards. The linear pick-up pattern microphones are equispaced about the perimeter of the frame. There is a hand or camera grip depending downwards from the frame. The microphones of the frame can be electronically connected to the respective channels of a multi-channel sound system, or to the channels of a multi-channel digital mixer which in turn can be connected to a multi-channel sound recording device. The microphones may be selectively electronically connected and disconnected to adapt the system for a predetermined sound playback configuration.

Abstract: A portable computer has a base unit, a first printed circuit board and a second circuit board. The base unit has a bottom wall and a connector panel which extends upward from a bottom wall. The first printed circuit board is mounted on the bottom wall, and has a first stacking connector. A second stacking connector is connected to the first stacking connector. A reinforcing plate is disposed on an upper surface of the second stacking connector. A bracket is arranged from the connector panel to the upper surface of the second stacking connector. The second circuit board is mounted on an upper surface of the bracket, and disposed above the first printed circuit board. A flexible wiring board is electrically connected to the second stacking connector and the second printed circuit board. The second printed circuit board is electrically connected to the first printed circuit board via the first and second stacking connector and the flexible wiring board.

Abstract: A microphone boom mounting device has two portions, a track portion and a truck portion which moves along the track. The truck portion has a boom mount suitable for mounting a microphone boom. The movable microphone boom mounting device is mounted above a television or a motion picture production stage in a catwalk located above the stage. The track portion is formed in a "T" shape, and the truck portion has wheels which engage the top and bottom surfaces of the top part of the "T" section of the track. By moving the truck along the track, a microphone boom attached to the boom mount on the truck portion can be moved from side to side above the stage, such that a single microphone mount is all that is required to follow the actors on the stage in different sets on the stage and ensure a high quality sound recording.

Abstract: An end fire microphone array having reduced analog-to-digital converter requirements is disclosed. Analog filters are used to band-limit at least two secondary microphone elements which are spaced from a primary microphone element a distance respective of their band limited outputs. The band-limited secondary microphone outputs are combined by an analog summer and the primary microphone and combined secondary microphone signals are digitized by an analog-to-digital converter. A signal processor performs a super-directive analysis of the primary microphone signal and the combined secondary microphone signals.A steerable superdirective microphone array is disclosed. A plurality of microphones are arranged in a ring. The microphone outputs are digitized, split into frequency bands, and weighted sums are formed for each of a plurality of directions. A steering control circuit evaluates the relative energy of each directional signal in each band and selects a microphone direction for further processing and output.

Abstract: A sound input apparatus according to the present invention subtracts, from the output signal from a first microphone, the output signal of a second microphone which is arranged in a manner different from that of the first microphone to output the subtracted signal and controls the level of the signal of the second microphone in response to the level of the subtracted signal. The sound input apparatus simply constructed in this way achieves a narrowed sound directivity when picking up sound and presents high-quality audio signal while keeping the influence of ambient noise to a minimum.

Abstract: An artificial head (2) and a plurality of discrete monophonic microphones (8, 10, 12) are used to record one or more sound sources. The signals (14, 16, 18) from each of the microphones (8, 10, 12) then undergo binaural synthesis based upon acoustical properties of a real human head or the artificial head (2), and the signals (4, 6) from the head are equalised using air-to-ear transfer functions of the artificial head (2) or a real head. The resultant signals are combined by summing the individual left (48) and right (50) channels together and then these summed signals (52, 54) are transaural crosstalk compensated (56) to provide final left and right channel signals (58, 60) suitable for recording or playback which provide a three-dimensional sound effect to a listener both via headphones and loudspeakers.

Abstract: A stereo ultradirectional microphone apparatus for detecting a sound to produce stereo sound signals, comprises: first and second ultradirectional microphones arranged side by side with a given distance in parallel for converting a sound into first and second sound signals respectively, first and second delays for delaying an output of the first and second microphones by a delay time .tau. respectively, and first and second subtractors for subtracting for subtraction between the first sound signal and an output of the second delay and subtracting for subtraction between the second sound signal and an output of the first delay. The delay time .tau. corresponds to a difference between the timings of a sound from a sound source in a direction making a clockwise angel .theta. from the front where a dead angel should be made. The subtraction provides the dead angle. Similarly, a dead angle on the side is also made to obtain a stereo characteristic.

Abstract: An autocalibration system includes two loudspeakers (2, 4) spaced from three microphones (16, 18, 20). Acoustic transient pulses are emitted by each loudspeaker (2, 4) in turn and from the reception of of these pulses by each of the microphones (16, 18, 20), the time-of-flight for each pulse to each microphone may be derived. From these time-of-flight measurements are also derived the distance and angular displacement of each microphone (16, 18, 20) from a reference point (12) flanked by the loudspeakers (2, 4).

Abstract: Disclosed is a device of the dummy head type for recording sound. It comprises a supporting body fitted with an anatomically faithful imitation of the human auricle. The auricle is coupled to a channel inside the body. This channel opens into the imitated auricle and corresponded to an auditory meatus of anatomical construction and length. It further comprises a microphone arranged behind the channel, such that the position of the membrane of the microphone relative to the imitated auditory meatus and auricle corresponds as much as possible to the anatomical position of the human eardrum relative to the associated auditory meatus and auricle. According to the invention, the channel has an open end on the side of the microphone and the microphone is arranged in front of this open end. A dummy head according to the invention comprises two devices as described, with the supporting plate of each mounted on opposite sides of a dividing plate by means of a bracket.

Abstract: In a small-sized pressure gradient type microphone apparatus, a plurality of omni-directional microphone units are encased within a microphone holder. A plurality of acoustic passages having first and second ends are provided within the microphone holder for coupling the sound inlets of the plurality of omni-directional microphone units respectively to an outer space of the microphone holder. The second ends of the acoustic passages opened to the outer space of the microphone holder are arranged to be apart from each other at distances larger than distances between the sound inlets of the corresponding microphone units coupled at the first ends of the acoustic passages.

Abstract: This invention relates to the presentation of sound where it is desirable for the listener to perceive one or more sounds as coming from specified three-dimensional spatial locations. In particular, this invention provides economical means of presenting three dimensional binaural audio signals with adjustment of spatial positioning parameters in real time.

Abstract: A method for reproducing sounds from signals, which are supplied from a same sound source through a pair of localization filters by using a pair of transducers disposed apart from each other and for controlling the localization of a sound image in such a way to make a listener feel that he hears sounds from a virtual sound source which is localized at a desired sound image location being different from the positions of the transducers. When performing this method, a signal for measurement reproduced at each sound image location is measured at the listener's position as data to be used for estimating head-related transfer characteristics. Then, the head-related transfer characteristics corresponding to each sound image location are estimated from the measured data.

Abstract: A method of detecting localization of an acoustic image, in which an acoustic impulse is emitted from a sound source to a dummy of a human head, an acoustic sensor is provided to a portion of the dummy's ears, and the response waveform is received by the acoustic sensor. This enables the detection of what effects are derived from interruption, reflection, and the like of a tone due to the human head. The received response waveform is analyzed and parameters for an acoustic image localization system are obtained. The acoustic image localization system comprising a delay circuit, a filter and an amplification controller sets the parameters into the delay circuit, the filter and the amplification controller, so that the detected localization of an acoustic image is reproduced.

Abstract: A small AM/FM audio player, operating as a radio, tape, cassette or disc machine can be adjusted to receive music or other audio programs. The received programs can be heard audibly through a stereo Y-adapter set of earphones, and also through a set (pair) of stereo microphones which are clamped by spring loading on to a stereo microphone of a camcorder. The small AM/FM audio player can be programmed to emit any desired program and can be audited by personnel simultaneously with recording the audio program. Thus the picture being shown by the camcorder can be concurrently coordinated with the audio messages inexpensively.

Abstract: The insertion effects of hearing aids are determined and compensated to restore the ability to have directional hearing in individuals wearing hearing aids. In one aspect a method involves finding the ratio of the unaided head related transfer function to the aided head related transfer function and then designing a hearing aid filter that is the inverse of that derived insertion effect, thereby restoring the ability to hear interaural differences in aided systems both in level and in time of arrival to improve hearing in the presence of noise. The insertion effects can be derived either through frequency domain analyses, using the above-mentioned transfer function calculations and measurements, or in another aspect through time domain analyses, using optimal filter calculations and measurement obtained using a successive data acquisition system that is subsequently time aligned by recording trigger pulses with the data.

Abstract: A camcorder having a loudspeaker function has a recording device and includes an input device for receiving an external sound and converting it into a first electric signal and for receiving a sound from a user and converting it into a second electrical signal. The input device is preferably movable between an extended position and a retracted position. Sound processing means are provided and coupled to a speaker for outputting an amplified sound through the speaker. A switching device is provided for sending the first electrical signal to the recording device when the second input device is in the retracted position and for sending the second electrical signal to the sound processing device when the second input device is in the extended position.

Abstract: Disclosed is a camcorder comprising a microphone housing formed in one side of the body of the camcorder for receiving a microphone body, a microphone body received in the microphone housing so as to move forwards and backwards, a resilient means for resiliently supporting the microphone body, and a switching means for controlling a recording device of the camcorder according to the motion of said microphone body.

Abstract: A microphone apparatus comprises two non-directional microphones in case of monaural sound pickup or three non-directional microphones in case of stereo sound pickup, and a signal processing means for processing output signals of the non-directional microphones so that a directivity becomes non-directional in a low frequency region and a first order pressure gradient type in a high frequency region. Accordingly, the microphone apparatus can attenuate the level of unwanted acoustic and vibration noises caused by its onboard moving mechanism as well as wind noise, thus ensuring no declination in the S/N ratio during sound pickup action.

Abstract: A stereo microphone unit adapted to be installed in a video camera or the like, includes a cabinet, two nondirectional microphones disposed with a predetermined distance therebetween on respective walls of the cabinet for collecting an outside sound signal, delay circuits for delaying each output of the microphones by a time period corresponding to the predetermined distance, and signal subtractors for subtracting the output of the delay circuit relative to one microphone from the output of the other microphone. A stereo audio signal is provided only with regard to the output sound signal of any frequency lower than a predetermined frequency of 6 kHz or so.

Abstract: An apparatus for producing pseudo-stereophonic sound from a monaural signal including a monaural source having a first speaker disposed in an anechoic room and having a sound output generated by the monaural signal. Second, third, fourth and fifth speaker disposed in the anechoic room (substantially) symmetrically about a listener having two ears. The monaural signal from the source is processed to output processed signals to each of the second, third, fourth and fifth speakers, each speaker producing a sound output corresponding to the received processed signal. A pair of microphones are disposed in the ears of the listener for receiving the sound outputs of the first, second, third, fourth and fifth speakers and producing two differentiated audio channels.

Abstract: A process for evaluating spatial impression of an enclosed space includes the steps of generating output signals as a function of fluctuating sound pressure at two points spaced about one-quarter meter apart, band limiting the output signals to a pass band of less than about one octave, generating fluctuating signals that represent amplitude information of the band limited output signals, band limiting the fluctuating amplitude information signals to a pass band of about five hertz to thirty hertz, and comparing the band limited fluctuating amplitude information signals to provide an indication of the spatial impression of the enclosed space.

Abstract: A wiring harness is provided with a miniature speaker and attachment means for connecting the speaker to the microphone on a video camera. The harness is also provided with a plug for coupling the speaker to an audio play-back machine. In this manner a background of music may be laid down on the sound track of home-videos by direct audio input through the microphone pick-up on the video camera.

Abstract: A stereophonic microphone system for improving stereophonic hearing utilizes intensity stereophonic and/or time difference stereophonic pickup methods with the use of replicas of the human head. The microphones are mounted in the replicas of the outer auditory meatus. The replica of the human head is limited to replicas of the pinna with outer auditory meatus. In addition to the known stereophonic recording device used as a position association stage, two replicas of human pinnas are used, with pressure microphones in each opening of the auditory meatus as a shape association stage. The pinna replicas are arranged spaced apart and oriented on the human head or closely next to each other with the same orientation. The pinna replicas are arranged preferably immediately adjacent the arrangement of known directional microphones for the interaural sound recording in the horizontal and median planes.

Abstract: A stereo audio processing system for a stereo audio signal processing reproduction that provides improved source imaging and simulation of desired listening environment acoustics while retaining relative independence of listener movement. The system first utilizes a synthetic or artificial head microphone pickup and utilizes the results as inputs to a cross-talk cancellation and naturalization compensation circuit utilizing minimum phase filter circuits to adapt the head diffraction compensated signals for use as loudspeaker signals. The system provides for head diffraction compensation including cross-coupling while permitting listener movement by limiting the cross-talk cancellation and diffraction compensation to frequencies substantially below approximately ten kilohertz.

Abstract: A device for the stereophonic recording of sound events by means of two microphones arranged with essentially oppositely directed orientation and mounted in replicas of the human head. The microphones are mounted in the replicas of the outer auditory meatus. The replica of the human head is limited to the replicas of the pinnae with the outer auditory meatus. Microphones with unilateral pickup effect are used and are mounted preferably in positions corresponding to the positions of the pinna openings in human heads. The microphones operate in the low-frequency range of up to approximately 1500 Hz as directional microphones and, in the frequency range above approximately 1500 Hz, operate with spectral resolution of the outer ear transmission function. The device according to the present invention provides compatibility of headset reproduction and loudspeaker reproduction.

Abstract: A multi-channel electronic visual aid device which is able to signal to the user whether sound is coming from the left or right, front or back, or both. For the plurality of channels, which may operate in pairs, the sound is picked up by a respective microphone and amplified and rectified into a DC voltage. The DC voltage is next fed to an analog to digital converter and then to a digital encoder. The binary code from the encoder is coupled into a logic circuit where the binary code is decoded to provide a plurality of output levels which are used to drive an indicator which, in turn, provides a visual indication of the sound level received. The binary codes for each pair of channels are also fed into a digital comparator.

Abstract: Device for listening to and recording of the sounds produced by birds or other distant objects. The device (FIG. 1) is attached to a pair of binoculars or a telescope and consists of one or more directional microphones, microphone structures or sets of microphones, a microphone and headphone amplifier and a pair of headphones, the directional microphone structures (2, 3) and the amplifier unit (4) with the headphones (7) being attached to the binoculars (1) by suitable means. An audio signal can be supplied from the amplifier to an external recording device, or a recording device may be integrated with the device of the invention. Used together with a pair of binoculars or a telescope, the device provides a light and easy-to-use means of audiovisual observation of distant objects, and when provided with an integral or external tape recorder it is also suited for amateur use for the recording of wildlife sounds.

Abstract: A stereo audio processing system for a stereo audio signal processing reproduction that provides improved source imaging and simulation of desired listening environment acoustics while retaining relative independence of listener movement. The system first utilizes a synthetic or artificial head microphone pickup and utilizes the results as inputs to an equalization circuit with the outputs coupled to a cross-talk cancellation compensation circuit utilizing minimum phase filter circuits to adapt the head diffraction compensated signals for use as loudspeaker signals. The system provides for head diffraction compensation including equalization and cross-coupling while permitting listener movement by modifying the cross-talk cancellation and diffraction compensation at frequencies substantially above approximately ten kilohertz while maintaining substantially accurate equalization for the desired incidence angle.

Abstract: An audio signal recording system comprising a first apparatus for generating a sum signal of left and right signals of a stereophonic audio signal and a difference signal of the left and right signals, and a second apparatus for recording on a recording medium the sum signal and the difference signal which have been generated by the first apparatus, without converting the sum signal and difference signal into the left and right signals.

Abstract: A stereo microphone that delivers "Right" and "Left" output signals from the sound field at a single point in space. A small, light, ball-like sound-sensing element is loosely suspended so that it is free to move in any direction in a plane. Directional components of its displacements are sensed and translated into electrical analog signals, which are then processed to provide separate stereo outputs. The sound-sensing element may be suspended on an optical fiber and its displacements sensed by a quad photodetector, whose four outputs are added and subtracted in certain combinations to derive the stereo outputs.

Abstract: A stereo audio processing system for a stereo audio signal processing reproduction that provides improved source imaging and simulation of desired listening environment acoustics while retaining relative independence of listener movement. The system first utilizes a synthetic or artificial head microphone pickup and utilizes the results as inputs to a cross-talk cancellation and naturalization compensation circuit utilizing minimum phase filter circuits to adapt the head diffraction compensated signals for use as loudspeaker signals. The system provides for head diffraction compensation including cross-coupling while permitting listener movement by limiting the cross-talk cancellation and diffraction compensation to frequencies substantially below approximately ten kilohertz.

Abstract: A stereo dimensional recording method and microphone apparatus which produces a quality stereo signal output, that, when combined with any stereo audio recorder, allows the recording professional and amateur enthusiast excellent stereo sound with depth dimension realism independent of sound stage distances when reproduced by both headphones and loudspeakers without the need for additional frequency or phase processing equipment/circuits. The apparatus is virtually visually unobtrusive when personally worn on the user's head by means of a variety of mounting accessories, is unfatigueing when in use, does not impair the hearing of the wearer, and does not interfere with live listening enjoyment during recording.

Abstract: An adapter converts a monaural microphone unit for stereophonic operation. The adapter has an elongate cylindrical housing including an input jack which rigidly attaches to the microphone and receives the microphone signal and an output jack which makes stereophonic signals available to recording equipment. Two distinct signal transmission channels are present in the adapter for transmission of the microphone signal to the output jack. A gravity-responsive switch selects which of the two transmission channels is active depending on the orientation of the adapter housing relative to vertical. An interviewer maintains the adapter and microphone in a vertical orientation or inclined towards him to record his questions along one channel and tilts the adapter unit towards his subject to record the response on the other signal channel. Resistors couple the two transmission channels to ensure that the non-active signal channel is not silent but at least carries the microphone signal in attenuated form.

Abstract: By means of an active filter with free-field sound exposure from the front, a system is provided which assures a frequency response of a microphone's transmission functions which is comparable with that of a measurement microphone, so that this system on the one hand analyzes acoustic phenomena in the conventional manner and, additionally, in the case of reproduction via a free-field, distortion-corrected headset to the eardrums of a listening person, generates the same sound pressure signals as if the person were located at the place of sound recording, while, on the other hand, in the case of reproduction via loudspeakers no annoying acoustic contamination occurs. The entire artifical head system is designed for either a.c. or battery operation and is combined with an analog or digital recording unit to produce a self-sufficient recording and reproduction system.

Abstract: The acoustic transmission characteristics of a sound field, such as in the passenger compartment of a vehicle, are measured by placing microphones at the positions of ears of a dummy mannequin having a sound absorbing characteristic similar to that of a clothed adult human. The transmission characteristics are then corrected, such as with an automatic graphic equalizer, to provide optimized listening conditions inside the sound field for an actual listener. The use of the invention results in a listener's perception of completely natural sound.

Abstract: A microphone system comprising a pair of microphone capsules, a pair of planar barriers positioned at an angle to each other, with each microphone capsule secured to the center portion of a barrier positioned between the microphone capsules. A baffle is positioned between the microphones with the sidewalls of the baffle extending angularly toward the barriers forming corners with each of the microphone capsules located at the corner.

Abstract: An infrared headphone with supplemental microphones to aid the hearing impaired allowing the user to hear the significant sounds from the ambient surroundings. In order to suppress the sound intensity of the user's own voice the invention provides for microphones arranged at a distance from each other on a supporting elbow in such a way that when they are mounted on the head of the user they are symmetrically arranged with respect to a median plane of the user's head and the signals emitted from the microphones are conducted in counter-phase with respect to each other.