Abstract: An apparatus and method is provided for transmitting “masked” stereo audio signals in a signal distribution network such as a cable television system within the bandwidth constraints of conventional frequency allocation schemes. In various embodiments, left and right stereo audio signal components (L+R and L−R) are used to amplitude modulate a carrier using independent sideband (ISB) modulation without the transmission of a pilot signal. A jamming signal or low bandwidth data signal may be transmitted in place of the normal pilot tone. Various aspects of the invention contemplate the use of Hilbert transforms to perform the ISB modulation and demodulation.

Abstract: A synchronized sounding/flashing circuit includes a sound synthesizer stored with sound data and emitting sound signal upon being supplied with power, a digital-to-analog converter connected to the sound synthesizer for converting the sound signal to an analog signal for driving an external speaker, a sound level/density detector connected to the sound synthesizer for generating a detected signal in response to the sound signal therefrom, a frequency generator being connected to the sound synthesizer and triggered thereby when the sound synthesizer outputs the sound signal and outputting a signal having a frequency according to the detected signal, a flasher being connected to the sound synthesizer and triggered thereby when the sound synthesizer outputs the sound signal, and being connected to the frequency generator for sequentially and alternately outputting a pulse from a plurality of output terminals thereof with a frequency proportional to the frequency of the signal outputted from the frequency generat

Abstract: The system and method of the present invention provides enhanced surround sound effects. In one embodiment, 90.degree. phase shift and copy of the 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. This provides the audible effect of distinguishing more clearly sounds originating in front of the listener or to the rear of the listener while not limiting the perceived bandwidth of the signal. The rear signals corresponding to the first channel are inverted. The front and rear signals for each corresponding channel are then combined. The two channels, generated can be stored on media, such as film, and subsequently read and input to a surround sound decoder to generate enhanced surround sound output.

Abstract: A sound image localization device includes a delay circuit and a multiplier which cooperate to cause a time difference and an amplitude difference between left and right channel audio signals. One of the channel audio signals is inverted in phase. The channel audio signals thus having a time difference and an amplitude difference, with one of them being inverted in phase, are amplified by an amplifier and outputted through left and right loudspeakers as sound, whereby a sound image formed by the audio signals can be localized at a rearward position with respect to the listener.

Abstract: This invention regards a method and an arrangement for attenuating undesirable high amplitude output sound of an acoustic system 2 by injecting a canceling sound produced by a controller 10 and radiated by a loudspeaker 12. The controller 10 has a nonlinear transfer behavior between the control input 20 provided with the sensed input noise and the output 26 connected to the loudspeaker 12. The architecture of the nonlinear controller 10 is directly derived from an acoustic model describing the nonlinear sound propagation in the acoustic system 2. The control architecture can be implemented in a digital signal processor with a minimum of elements and improves the efficiency of the active attenuation so that the fundamental and the nonlinear distortions of the sound can be canceled and the output noise level is lower than by using a linear control system.

Abstract: Techniques for reducing unwanted acoustic feedback in a space are carried out by an adaptive notch filter algorithm that adjusts a notch to a plurality of different notch values in order to locate feedback. The results obtained by performing the algorithm at various notch values are compared. Based on the comparison, the parameters for the algorithm are adjusted for processing of the input signals to reduce the feedback.

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 spectrum display device for audio use includes a first differential amplifier circuit and a first capacitor forming a low pass filter. A second differential amplifier circuit and a second capacitor form high pass filter; A band pass filter circuit is formed by the low pass filter and the high pass filter; A band selection circuit selectively sets a frequency band of the band pass filter circuit out of a plurality of predetermined frequency bands through selective setting of the operating currents of the first and second differential amplifier circuits.

Abstract: An audio signal transmission line including capacitive and/or inductive networks connected in series or parallel with an audio transmission cable providing for increased storage of electrical energy, and thereby overcoming energy storage problems associated with previous audio signal transmission systems which create unwanted pre-emphasis of audio signals at certain frequencies.

Abstract: A noise reducing microphone apparatus having an adaptive noise canceller which has a primary input and a reference input and in which the reference input is subtracted from the primary input through an adaptive filter and the adaptive filter is adaptively controlled by an output signal resulted from the subtraction, comprises. The apparatus includes a pair of microphone units disposed in proximate locations; and subtracting means for performing subtraction of outputs from the pair of microphone units. An output from one of the microphone units is supplied as the primary input of the adaptive noise canceller. A differential output from the subtracting means is supplied as the reference input of the adaptive noise canceller.

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 surround sound encoder, intended for implementation in software, runs in real time on a personal computer using low mips and a small fraction of available CPU cycles. In the principal application for the encoder, the Lt and Rt signals of the encoder are mixed with the Lt and Rt signals of a pre-recorded source (e.g., computer game soundtrack, CD ROM, Internet audio, etc.). Alternatively, the encoder may be used by itself or with one or more other virtual encoders to provide a totally user-generated soundfield. The encoder is implemented in either of two ways: the signal being encoded may be panned to one or more of the four inputs of a surround-sound fixed matrix encoder or the signal may be encoded by applying the signal to a surround-sound variable-matrix encoder.

Abstract: A position tracker uses an inertial angular measurement system, for measuring orientation and linear translation of a helmet on a human head for the synthesis by a host computer of virtual, directional audio over headphones sensors mounted on the helmut, includes a roll gyro sensor, a pitch gyro sensor, a yaw gyro sensor, an absolute roll tilt sensor coupled to a first universal signal conditioner, an absolute pitch tilt sensor coupled to a second universal signal conditioner, and an absolute yaw compensator. A data acquisition system is coupled between the sensors and the host computer for converting analog signals from the sensors into digital, angular orientation data. Each of the gyro sensors includes angular velocity detectors and solid state electronic devices connected to provide angular velocity signals at a given sample rate.

Abstract: An audio effects processing system and method performs audio effects processing on a subband-by-subband basis using less memory and computational resources than audio effects produced through post processing of a fullband audio signal. The input fullband audio signal is split into subbands and the compressed subbands may be stored in memory of the system as compressed audio subband data or may be generated by real time processing of a fullband audio signal. The system stores in memory a set of prototype subband effects filters, the set including echo, flange, chorus, and reverberation effects filters. A subband filter customization procedure allows a sound system designer to build customized versions of the prototype subband effects filters. One or more of the customized subband effects filters are applied to one or more of the subbands comprising the compressed audio subband data.

Abstract: An audio tremolo producing system uses a rotating horn as a tremolo producing device for mid and high frequency audio signals, and an electronic tremolo producing device capable of both phase and amplitude modulation for low frequency signals.

Abstract: An active noise conditioning system for use with a combustion engine exhaust system is provided. A controller receives an exhaust noise signal, along with various other feedback signals for producing an anti-noise signal in response to the input signals. An amplifier is provided for receiving and amplifying the anti-noise signal. A wave generator receives the amplified anti-noise signal and generates an audio anti-noise signal. The output of the wave generator is collocated with the exhaust pipe of the exhaust system, where the audio anti-noise signal and the exhaust noise are acoustically coupled, which effects cancelling of the exhaust noise.

Abstract: A system for attenuating noise which can be sensed by the auditory nerve comprising a microphone positioned in a first sound region for sensing noise present in the first sound region for creating a first electrical signal having a frequency and amplitude corresponding to the noise sensed in the first sound region. Circuitry is provided for processing the first electrical signal to create a second electrical signal having the same frequency but of opposite amplitude and sign of the first electrical signal. A speaker is provided for converting the second electrical signal to anti-noise for attenuation of the sensed noise in a second sound region spaced from the first sound region. A microphone is disposed in the second sound region for detecting any noise above a predetermined noise level in the second sound region to provide an error correction signal.

Abstract: A vibration control system includes a processor-based circuit which monitors and controls an analog vibration control circuit. The system include, a sensor to detect the undesirable vibrations and a synchronous pulse generator for determining the fundamental frequency of the vibrations emitted by the source. An actuator produces anti-noise to counter unwanted vibrations. The processor circuit tests the system, monitors system functions, and adjusts various parameters to provide optimal performance.

Abstract: In a method for the adaptation of the transmission characteristic of a hearing aid to the hearing aid impairment of a hearing aid wearer using a personal computer having a pointer device such as a mouse, the acoustician selects segments of the graphic presentation of the hearing aid parameters with the mouse, modifies the graphics point-by-point or segment-by-segment by displacement of the mouse and thereby correspondingly co-modifies appertaining, displayable parameters. The hearing aid can be adapted to reach a target characteristic by means of one adaptation procedure, followed if necessary by further analogous fine adaptation procedures.

Abstract: A method and apparatus for mixing audio signals. Each audio signal is digitized and then transformed into a predefined visual image, which is displayed in a three-dimensional space. Selected audio characteristics of the audio signal, such as frequency, amplitude, time and spatial placement, are correlated to selected visual characteristics of the visual image, such as size, location, texture, density and color. Dynamic changes or adjustment to any one of these parameters causes a corresponding change in the correlated parameter.