Abstract: A stereophonic sound processing system for localizing a sound image at desired locations using devices including a headphone and a speaker, includes a processing unit for generating stereophonic sound on the basis of an input signal. The processing unit includes: a plurality of stereophonic filter units each including an FIR filter for processing an input signal; a selecting unit for selecting one of the plurality of stereophonic filter units in accordance with a desired factor; wherein the processing unit controls the selected stereophonic filter unit so as to generate stereophonic sound on the basis of a processed result supplied by the selected stereophonic filter unit.

Abstract: A wireless headphone/speakers sound field control system, which includes a wireless signal receiver, a left speaker connected to the wireless signal receiver through a left differential amplifier and a left variable resistor, and a right speaker connected to the wireless signal receiver through a right differential amplifier and a right variable resistor, each of the left and right variable resistors being respectively connected to the positive pole of each of the left and right differential amplifiers, wherein a phase-shifting circuit is connected between the left differential amplifier and the right differential amplifier, having two sub-circuits each formed of a first capacitor, a variable resistor, a second capacitor and a resistor, each sub-circuit being connected in series between the right or left variable resistor and the left or right differential amplifier, the phase-shifting circuit enabling the differential amplifiers to have a dual signal input, so that left sound channel signal is inputted into

Abstract: A system for generating loudspeaker-ready binaural signals comprises a tracking system for detecting the position and, preferably, the angle of rotation of a listener's head; and means, responsive to the head-tracking means, for generating the binaural signal. The system may also include a crosstalk canceller responsive to the tracking system, and which adds to the binaural signal a crosstalk cancellation signal based on the position (and/or the rotation angle) of the listener's head. The invention may also address the high-frequency components not generally affected by the crosstalk canceller by considering these frequencies in terms of power (rather than phase). By implementing the compensation in terms of power levels rather than phase adjustments, the invention avoids the shortcomings heretofore encountered in attempting to cancel high-frequency crosstalk.

Abstract: A BTSC-compatible encoder that is integrated onto an application specific integrated circuit includes a low pass filter that is responsive to a digital representation of an audio signal that has a sample rate of FS. The low pass filter generates a corresponding second digital signal having an pseudo-interpolated sampling rate of 4FS. A digital infinite impulse response pre-emphasis filter generates a pre-emphasized output signal corresponding to the second digital signal. A digital signal compressor that is responsive to the pre-emphasized output signal, generates a compressed digital signal corresponding to the pre-emphasized output signal. A digital phase locked loop that is responsive to a video sync pulse having a sync pulse frequency, generates a third digital signal corresponding to a sinusoid having a frequency equal to twice the sync pulse frequency and a having a sampling frequency equal to 4FS.

Abstract: A system produces, based on samples of a single-channel input audio signal and an indication of a particular orientation of the listener relative to a source of the audio signal, a multi-channel output audio signal that emulates an audio signal as emanating from the source having the particular orientation to the listener. Interaural time delay (ITD) circuitry generates, from the single-channel input audio signal, a first left channel audio signal and a first right channel audio signal, wherein the first left channel audio signal and the first right channel audio signal are each based on the single-channel input audio signal but differ from each other at least with respect to phase based on the indication of the particular orientation. Azimuth frequency compensating (AFC) circuitry modifies the first left channel audio signal and the first right channel audio signal based on an azimuth, relative to the listener's left ear and right ear, respectively, of the particular orientation.

Abstract: A system is disclosed for steering a monaural audio signal representing a source of sound into left and right audio signals for presentation to the corresponding ears of a listener so that the listener perceives the sound source in a specific location relative to his head. The left and right signals may be provided through headphones or loudspeakers, in the latter case employing techniques to cancel the crosstalk from each loudspeaker into the opposite ear of the listener. The monaural audio signal is filtered using head-related transfer functions (HRTFs) into the left and right outputs, these being equivalent to the acoustic HRTFs that would be generated if a source of sound were placed at the specific location relative to the listener.

Abstract: The system of the present invention includes, briefly, a point source speaker system, comprising a processor which produces a left minus right (L−R) audio signal, a right plus left (R+L) and a right minus left (R−L) audio signal; three speakers each for audibly transmitting one of the L−R, R+L and R−L audio signals; and a point source speaker enclosure for housing the three speakers in a single enclosure.

Abstract: A stereophonic sound system is disclosed, having a source of stereophonic signals which contain a right signal and a left signal as well as further signals which supplement the right and left signals to convey a three-dimensional sound impression. The right and left signals are adapted to a stereo base of a pair of loudspeakers having a correspondingly small size by means of a modification circuit. Of the stereophonic signals, only the right and left signals are fed to the modification circuit so that they are falsified as little as possible. An improved system for conveying a three-dimensional sound impression is thus provided.

Abstract: A method and apparatus for simulating the transmission of sound from sound sources to the ear canals of a listener encompasses novel head-related transfer functions (HTFs), novel methods of measuring and processing HTFs, and novel methods of changing or maintaining the directions of the sound sources as perceived by the listener. The measurement methods enable the measurement and construction of HTFs for which the time domain descriptions are surprisingly short, and for which the differences between listeners are surprisingly small. The novel HTFs can be exploited in any application concerning the simulation of sound transmission, measurement, simulation, or reproduction. The invention is particularly advantageous in the field of binaural synthesis, specifically, the creation, by means of two sound sources, of the perception in the listener of listening to sound generated by a multichannel sound system.

Abstract: A spatial enhancement system broadens the sound image of a stereo signal. The system emphasizes dissimilarity between the left and right channels by (i) boosting the level of the dissimilar components, (ii) providing spectral equalization to enhance the perception of breadth, and (iii) injecting an equalized, attenuated and inverted version of the dissimilar component into the opposite channel to broaden the components stereo image. The present invention avoids spectral coloration by providing a generally flat transfer function from input to output. Interchannel dissimilarity is estimated by performing a first order comparison of the left and right input signals. The comparison may be implemented by a peak detector on the L-R signal, a cross-correlation procedure, or some other scheme. As a feature, a feedback mechanism alters the equalization characteristics of the signals in a manner that is responsive to the dissimilarity of the output signals.

Abstract: Digital audio signal transmission is provided for digitally processing, for transmission in a digital VCR format, audio signals from a plurality of channels into a digitized audio data segmented into blocks having a data size, each block reserved for audio data digitized from one of the channels. The audio data is converted from the channels into the blocks of digitized audio data by varying the data size of the blocks. The audio data is composed by scaling the audio data in at least one of the blocks and combining the scaled audio data with the audio data of another of the blocks into a block reserved for composite audio data.

Abstract: The present invention is concerned with an audio equipment capable of processing video signals and a method of displaying operation of the acoustic equipment. An input selector switch 1 is supplied with reproduced audio signals from devices connected to a tuner unit 2 and input terminals 3, and supplies a signal to a sound field processing DSP unit 4. A signal processed by the DSP unit 4 is applied through a muting switch 5 to an output terminal 6. An input selector switch 7 is supplied with reproduced video signals from devices connected to input terminals 8, and supplies a signal to a graphic controller (GDC) 9 which generates a video signal to display an image. One of a signal generated by the GDC 9 and an original video signal are selected by a switch 10, and applied to an output terminal 11. The GDC 9 also generates an image simulating a control panel. When a key switch 13 is operated, the display corresponding to the operated key in the simulating image is varied.

Abstract: It is an object of the present invention to provide an apparatus for localizing a sound image capable of achieving so called "surround-effect" sufficiently with a simple structure while maintaining a sufficient width of a frontal sound field. Both surround left and surround right signals SL, SR are supplied to a sideward localizer 12 for localizing the sound image reproduced by the signals to positions of sideward of a listener. Also, front left and front right signals FL, FR are supplied to the sideward localizer 12. In this way, the sound image reproduced by the signals is localized at positions between speakers arranged in front side and sidewards of the listener, so that a sufficient width of frontal sound field can be maintained eventually.

Abstract: A surround signal processing system receives a surround signal and also a program of processing the surround signal. The received surround signal is decoded into multiple-channel signals according to the received program. The multiple-channel signals include a left surround signal and a right surround signal. The multiple-channel signals are converted into two-channel signals according to the received program. The two-channel signals are transmitted to a pair of loudspeakers respectively. During the conversion of the multiple-channel signals into the two-channel signals, the left surround signal and the right surround signal are subjected to filtering processes according to the received program so that the left surround signal and the right surround signal will be converted into filtering-resultant signals. The two-channel signals are generated on the basis of the filtering-resultant signals.

Abstract: A method of entering an audio signal into a data processing apparatus, in which analog audio signals of at least two channels as the audio signal are digitized by and transmitted from an audio signal output device on a side of an audio source to an audio signal input device on a side of the data processing apparatus. A clock signal is supplied from the audio signal input device to the audio signal output device. The audio signal output device performs delta-sigma (.DELTA..SIGMA.) modulation on the analog audio signals of at least two channels so as to convert each of the analog audio signals of at least two channels into one-bit digital audio data for each of the at least two channels, based on the clock signal supplied to the audio signal output device. The one-bit digital audio data for the each channel is alternately selected based on the clock signal, to perform time-division multiplexing on the one-bit digital audio data for the at least two channels, to thereby produce one-bit multiplex audio data.

Abstract: A stereophonic image enhancement signal processing system for vehicular sound systems provides a symmetrical improvement in imaging for listeners located at the left and right regions of a vehicle passenger compartment The stereo signals are processed in a manner to provide a rapid rate-of-change of phase equal to at least 90 degrees per octave approaching a maximum of 180 degrees between the stereo channels at approximately 300 Hz. A further enhancement of the reproduced sound stage is provided through the application of equalized stereo difference signals prior to, and in combination with, the above described phase shift process. An optional center channel signal, summed from stereo source signals, may be provided for driving a central speaker.

Abstract: A sound image control apparatus is arranged by a time difference signal producing unit, and a function processing unit. The time difference producing unit sequentially outputs externally supplied input signals as a first time difference signal and a second time difference signal while giving an inter aural time difference corresponding to a sound image localization direction. This second time difference signal is externally outputted as a left channel signal. Also, the first time difference signal is processed in the function processing unit by using a relative function constituted by a ratio of a left head related acoustic transfer function to a right head related acoustic transfer function in correspondence with the sound image localization direction, and the processed signal is externally outputted as a right channel signal.

Abstract: A signal regulator regulates an auxiliary signal based upon a primary signal scaled by an external amplifier. The signal regulator receives the primary signal with an unscaled level. Processing circuitry monitors the unscaled level of the primary signal. The primary signal is then output to the external amplifier for scaling, either by amplification or attenuation. The primary signal with a scaled level is in turn received by the signal regulator from the amplifier. The processing circuitry monitors the scaled level of the primary signal from the amplifier, and then generates a gain factor based upon the unscaled level and the scaled level of the primary signal. An auxiliary signal is received by the signal regulator. Adjusting circuitry receives the gain factor from the processing circuitry and adjusts a level of the auxiliary signal based upon the gain factor. The auxiliary signal with the adjusted level is then provided to an external component, for example, a loudspeaker.

Abstract: A system and method are disclosed for providing a two channel signal to the ears of a listener through an audio system. The audio system includes a plurality of audio signals which are played through a plurality of loudspeakers. A plurality of propagation paths exist from the loudspeakers to the ears of the listener. Crosstalk is canceled in the audio system by providing the two channel signal which is to be received at the ears of the listener as an input to a crosstalk compensating network. The crosstalk compensating network is operative to provide an inverse crosstalk signal which cancels the crosstalk caused by the propagation of the audio signals from the plurality of loudspeakers along the plurality of propagation paths to the ears of the listener.

Abstract: An acoustic signal processing subsystem for an electronic stereophonic audio system is disclosed. The acoustic signal processing subsystem will modify electronic audio signals such that sound broadcast from loudspeakers will be perceived as mimicking the quality of sound broadcast in an acoustically ideal room. The acoustic signal processing subsystem has a left signal processor coupled to a left acoustic signal source to modify the left acoustic signal and to couple a first modified left acoustic signal to a left speaker, and a right signal processor coupled to a right acoustic signal source to modify the right acoustic signal and to couple a first modified right acoustic signal to a right speaker.

Abstract: A stereophonic audio signal processing arrangement for variably enhancing a stereo image, wherein the stereo image enhancement is reduced at high signal levels so as to reduce distortion. The arrangement is used in a stereophonic audio reproduction system for enhancing the stereo image, which system may be part of an audio-visual reproduction system.

Abstract: The system and method of the present invention provides surround sound effects through a two channel system. In one embodiment, the first channel is connected to one speaker (e.g., the right speaker) of a headset and the second channel is connected to the other speaker (e.g., the left speaker) of the headset. Thus, surround sound effects, including providing effects to distinguish front and rear sound sources, are provided through headsets which isolate the sound provided to right ear and the left ear of the listener. Alternately, the signals are output to a two speaker system, enabling surround sound effects to be output through home stereo systems not necessarily configured specifically for surround sound. Modified head related transfer functions (HRTF) are applied to each rear sound signal. The modified HRTF for each rear signal is generated by removing the head related transfer function corresponding to the front center signal from the HRTF corresponding to the rear sound signal.

Abstract: A stereophonic sound image enhancement apparatus subtracts a right input signal from a left input signal and amplifies the subtracted signal to produce a difference signal, and also subtracts a right crosstalk signal from a left low-frequency-range enhanced signal obtained by filtering the left input signal. Then, the difference signal is added to this subtracted signal, and the added signal is outputted as a left output signal. Also, the left crosstalk signal is subtracted from a right low-frequency-range enhanced signal obtained by filtering the right input signal, and the difference signal is subtracted from the subtracted signal to output the subtraction result as a right output signal.

Abstract: An audio teleconferencing apparatus and method provide an audio sound field among a plurality of teleconferencees creating a sense of a virtual conference table having a spatial location for each conferencee at the virtual table. Each conferencee has a speakerphone including a programmable Digital Signal Processor (DSP) for receiving a conference audio signal. In one form, the speakerphones are coupled to a conference bridge through individual ports, the bridge linking together all conferencees for purposes of the multiparty teleconference and transmitting port identifying signals denoting at discrete instants of time which remote port has a currently speaking conferences. The port identity signals are transmitted in-band or out-of-band to the speakerphones in conjunction with the conference audio signal.

Abstract: A stereophonic audio processing system having left and right stereophonic sound channels with respective loudspeakers therefor is presented. The system is provided with spatial expansion of the stereophonic sound so that a first pair of spaced-apart loudspeakers will acoustically appear to be spaced further apart then they actually are. The audio system is provided with provisions for connecting a second pair of loudspeakers which can be spatially located at a distance between the loudspeakers which is larger than the first pair of loudspeakers. The audio system is provided with apparatus for providing stereo sound without spatial expansion when such secondary loudspeakers are used.

Abstract: A radio with a tuner and other program sources uses a digital signal processor (DSP) to enhance the audio signal and to generate a stream of digital data including audio data and control data corresponding to loudness functions. A fiber optic data link couples the data stream to a plurality of remote DSP modules each of which drive one or more speakers. Each module contains a user programmed DSP, a digital to analog converter and an amplifier for each associated speaker. The DSP modules are identical except for software parameters which establish a transfer function and a loudness characteristic for each speaker. The same DSP modules and the same speakers can be used in several vehicle types and the system audio performance can be optimized by customizing software for each type of vehicle.

Abstract: A sound image localization control device reproduces an acoustic signal on the basis of a plurality of simulated delay times and a plurality of simulated filtering characteristics as if a sound image ware located on an arbitrary position other than positions of separately arranged transducers. A convolver which is main device of the sound image localization control device comprise of a plurality of delay elements having the plurality of simulated delay times for delaying an audio signal to constitute a direct sound signal and a plurality of reflection sound signals. And the convolver includes a plurality of Infinite Impulse Response filters for filtering the direct sound signal and the plurality reflection sound signals on the basis of the plurality of simulated filtering characteristics respectively.

Abstract: Monaural inputs are accepted for presentation to a pair of speakers. The output sound image from that pair of speakers is such that a listener will perceive that the sound is stereo and that certain sounds come from a non-existent center speaker and that other sounds come from locations beyond the physical boundaries of the two speakers. The system operates to preserve full tone range at both speakers and does not split the sound from a particular instrument between both speakers. The system can be used to provide sound signals to the rear speakers of a multiple speaker system when the sound input to the rear speakers is either monaural or stereo.

Abstract: An audio enhancement system and method for use in a surround sound environment creates a more diffuse and continuous sound field from a multi-channel, multi-speaker reproduction environment. Multiple audio source signals generated from an audio recording, which are intended for speakers placed in front of and behind a listener, are isolated into pairs and processed to create corresponding pairs of component audio signals. Each pair of component audio signals is generated, at least in part, from the information present in both corresponding audio source signals. The individual component audio signals are then selectively combined to form enhanced output signals so that each enhanced output signal is modified as function of a plurality of audio source signals.

Abstract: A three-dimensional sound processing system which provides a listener with three-dimensional sound effects by reproducing a sound image properly positioned in a reproduced sound field. A filter coefficient enhancement unit creates two difference-enhanced impulse responses by emphasizing the difference between two sets of acoustic characteristics pertaining to a listener's both ears, which are represented as impulse responses measured in an original sound field. Based on the two difference-enhanced impulse responses, a series of coefficients of a sound image positioning filter are determined for every possible location of the sound source. A coefficient memory unit stores various sets of such filter coefficients separately for each sound source location.

Abstract: A digital audio spatialization system that incorporates accurate synthesis of three-dimensional audio spatialization cues responsive to a desired simulated location and/or velocity of one or more emitters relative to a sound receiver. Cue synthesis may also simulate the location of one or more reflective surfaces in the receiver's simulated acoustic environment. The cue synthesis techniques are suitable for economical implementation in a personal computer add-on card.

Abstract: A sound field processor having amplitude/phase conversion circuits for left and right channels of a stereophonic signal. The amplitude/phase conversion circuits for left and right channels have substantially the same circuit structure. Each of the amplitude/phase conversion circuits has an inversion amplifier, an amplitude/phase characteristic changing circuit that changes amplitude and phase characteristics of an output from the inversion amplifier, and a feedback device that add outputs from the amplitude/phase characteristic changing circuit and outputs from the inversion amplifier to an input signal to generate a sum signal and feed back the sum signal to the inversion amplifier. An output from the inversion amplifier for the left channel and an output from the amplitude/phase characteristic changing circuit for the right channel are added by a first adder device.

Abstract: A stereophonic image may be enhanced by splitting the left and right input audio signals into a plurality of left and right output signals in a plurality of audio frequency bands and then generating left and right output audio signals from the left and right output signals based on the magnitude of the differences between corresponding left and right output signals and also based upon the absolute magnitude of the left and right input audio signals themselves. In particular, a stereophonic image enhancement device according to the invention processes a left input signal and a right input signal using a first spectrum analyzer and a second spectrum analyzer which output a plurality of left output signals and right output signals corresponding to a plurality of frequency bands in response to the corresponding left input signal and right input signal.

Abstract: Stereophonic sound reproduction apparatus comprising an input means (2) for producing binaural signals, cross-talk cancellation means, (10) loudspeaker means, (20, 22) headphone means, (26) and a switch means (12, 18, 24, 30, 32) which in a first position (plug 24 not inserted in socket 18) couples the binaural signals from the input means (2) to the loudspeaker means (20, 22) through the cross-talk cancellation means (10) and in a second position (plug 24 inserted in socket 18) renders the cross-talk cancellation means (10) inoperable and couples the binaural signals from the input means (2) to the headphones (26).

Abstract: An audio enhancement system and method for use receives a group of multi-channel audio signals and provides a simulated surround sound environment through playback of only two output signals. The multi-channel audio signals comprise a pair of front signals intended for playback from a forward sound stage and a pair of rear signals intended for playback from a rear sound stage. The front and rear signals are modified in pairs by separating an ambient component of each pair of signals from a direct component and processing at least some of the components with a head-related transfer function. Processing of the individual audio signal components is determined by an intended playback position of the corresponding original audio signals. The individual audio signal components are then selectively combined with the original audio signals to form two enhanced output signals for generating a surround sound experience upon playback.

Abstract: In portable stereo radio receivers and television receivers, the loudspeakers therein may be separated only by a limited amount. This severely restricts the stereo image created by the loudspeakers. A circuit arrangement for creating an expanded stereo image may be incorporated in such receivers. This circuit arrangement includes, for each stereo channel, a first and a second all-pass 0.degree.-180.degree. phase shifter, wherein the first phase shifter shifts the input signal by 90.degree. at a frequency of 10 KHz, while the second phase shifter shifts the input signal by 90.degree. at a frequency of 100 Hz. The output from the first phase shifter in the left channel is combined with the output from the second phase shifter in the right channel to form the left channel output signal. Similarly, the output from the first phase shifter in the right channel is combined with the output from the second phase shifter in the left channel to form the right channel output signal.

Abstract: An apparatus for automatically equalizing a personal multi-channel audio system, and a method therefor, are disclosed. White noises which are generated by a transfer characteristic measuring section are reproduced through speakers. Transfer signals from the respective speakers are collected through a microphone array at a listening position so as to transmit the collected signals to a transfer function calculating section. The transfer function calculating section calculates the transfer characteristics between the respective speakers and the listening position by utilizing the white noise and the collected signals. Then the sound characteristics of the respective sound channels are adjusted so that the transfer characteristics between the respective speakers and the listening position would be equalized. Further, phantom channels are synthesized and reproduced by utilizing the transfer functions and the installed speakers. Therefore, at the given environment, an optimum sound reproduction is obtained.

Abstract: The manipulation system and apparatus receives electronic signals which are to be processed and recorded for playback as enhanced stereophonic audio signals from two laterally spaced loudspeakers in front of the listener. The system and apparatus processes those signals to produce a conditioning signal, such as which would be produced by virtual room boundaries, which is heard together with the original signals so that an enlarged listening area is perceived by the listener. By amplitude and phase control of the signal to the two real speakers, the system and apparatus provide a means for control over the enhanced sound field. This enhanced sound field is perceived by the listener as being contained within boundaries larger than those normally reproduced by stereophonic speakers.

Abstract: In portable stereo radio receivers and television receivers, the loudspeakers therein may be separated only by a limited amount. This severely restricts the stereo image created by the loudspeakers. A circuit arrangement for creating an expanded stereo image may be incorporated in such receivers. This circuit arrangement first forms a combined monaural signal and a differential signal from the two stereo signals. The differential signal is then subjected to a phase shift. The phase-shifted differential signal is then matrixed with the combined monaural signal to form output stereo signals. When reproduced through stereo loudspeakers, the stereo image appears to be greatly expanded, beyond the limited placement of the loudspeakers.

Abstract: A stereo enhancement system processes the difference signal component generated from a pair of left and right input signals to create a broadened stereo image reproduced through a pair of speakers or through a surround sound system. Processing of the difference signal component occurs through equalization characterized by amplification of the low and high range of auditory frequencies. The processed difference signal is combined with a sum signal, generated from the left and right input signals, and the original left and right input signals to create enhanced left and right output signals.

Abstract: A method and a system for audio communication between a plurality of users at a plurality of sites utilizes a set of audio input sensors at each site. Each set of audio input sensors binaurally senses an auditory space in proximity thereto. A metaphorical representation of each of the sites is provided. Each metaphorical representation has a position which is variable within a metaphorical space. The metaphorical representations can be based upon, for example, a physical metaphor, a visual metaphor, an auditory metaphor, or a textual metaphor. The auditory space sensed at each site is combined to form at least one synthetic auditory space. The at least one synthetic auditory space is formed in dependence upon the position of each metaphorical representation within the metaphorical space. A binaurally perceivable auditory environment is produced at one or more sites based upon the at least one synthetic auditory space.

Abstract: A split-band coding system combines multiple channels of input signals into various forms of composite signals and generates spatial-characteristic signals representing soundfield spatial characteristics in a plurality of frequency subbands. The spatial-characteristics signals may be generated in either or both of two forms. In a first form, the signal represents measures of signal levels for subband signals from the input channels. In a second form, the signal represents one or more apparent directions for the soundfield. The type of the spatial-characteristics signal may be adapted dynamically in response to a variety of criteria including input signal characteristics. Temporal smoothing and spectral smoothing of the spatial-characteristics signals may be applied in an encoder. Temporal smoothing and spectral smoothing may be applied to gain factors derived from the spatial-characteristics signals in a decoder.

Abstract: A method of creating an impression of sound from an imaginary source to a listener. The method includes the step of determining an acoustic matrix for an actual set of speakers at an actual location relative to the listener and the step of determining an acoustic matrix for transmission of an acoustic signal from an apparent speaker location different from the actual location to the listener. The method further includes the step of solving for a transfer function matrix to present the listener with an audio signal creating an audio image of sound emanating from the apparent speaker location.

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: A method and apparatus is disclosed which spatially enhances stereo signals without sacrificing compatibility with monophonic receivers. In accordance with one embodiment of the present invention, a stereo enhancement system is implemented using only two op-amps and two capacitors and may be switched between a spacial enhancement mode and a bypass mode. In other embodiments, simplified stereo enhancement systems are realized by constructing one of the output channels as the sum of the other output channel and the input channels. In other embodiments, a pseudo-stereo signal is synthesized and spatially enhanced according to stereo speaker crosstalk cancellation principles. In yet other embodiments, the respective spacial enhancements of monophonic signals and stereo signals are integrally combined into a single system capable of blending, in a continuous manner, the enhancement effects of both.

Abstract: Acoustic signals received by the ears are controlled by feeding back and filtering the signal to be applied to the speaker, rather than by use of a feedforward filter. The feedback filter may incorporate an electrical model of the speaker-to-ear transfer function to force the ear signals to a desired ratio of amplitudes and phases as a function of the frequency. The signals to be output to the right and left channels are fed back through a filter to obtain a feedback signal. The feedback signal is subtracted from one input channel and added to the other input channel to provide the output signals. This technique may be used both in stereo spreading and in three-dimensional localization of a monaural sound source. By using feedback instead of feedforward, the system can be readily adapted to different playback environments. Through a simple adjustment of the electrical model of the speaker-to-ear transfer functions, this system automatically provides the desired ear signals.

Abstract: A stereophonic signal processing system for enhancing the perception of sonic dimension and imaging in a sound reproduction system having at least two stereo speakers.

Abstract: An acoustic correction apparatus processes a pair of left and right input signals to compensate for spatial distortion as a function of frequency when said input signals are reproduced through speakers in a sound system. The sound-energy of the left and right input signals is separated and corrected in a first low-frequency range and a second high-frequency range. The resultant signals are recombined to create image-corrected audio signals having a desired sound-pressure response when reproduced by the speakers in the sound system. The desired sound-pressure response creates an apparent sound image location with respect to a listener. The image-corrected signals may then be spatially-enhanced to broaden the apparent sound image.

Abstract: A method and apparatus is disclosed which spatially enhances stereo signals without sacrificing compatibility with monophonic receivers. In accordance with one embodiment of the present invention, a stereo enhancement system is implemented using only two op-amps and two capacitors and may be switched between a spacial enhancement mode and a bypass mode. In other embodiments, simplified stereo enhancement systems are realized by constructing one of the output channels as the sum of the other output channel and the input channels. In other embodiments, a pseudo-stereo signal is synthesized and spatially enhanced according to stereo speaker crosstalk cancellation principles. In yet other embodiments, the respective spacial enhancements of monophonic signals and stereo signals are integrally combined into a single system capable of blending, in a continuous manner, the enhancement effects of both.

Abstract: A software algorithm is disclosed which allows audio signals to be positioned discretely and dynamically in a 360.degree. environment, the center of which is assumed to be the position of the user-listener. The algorithm includes: a) proprietary knowledge of the sound sources (such as a synthesizer chip); b) proprietary knowledge of the number of independently addressable couplers (i.e. how many speakers are employed); and c) a software driver incorporated on a host, computer, or a stand-alone device which includes the algorithm for routing the sound sources to the transducers at the proper volume levels. In a preferred embodiment of the invention, the algorithm functions by controlling the amplitude attenuation of each source as it is coupled to the transducers, and the relationship of the amplitudes sent to each transducer by means of reference values contained in a matrix table native to the algorithm.