Abstract: A device and method for producing sound which simulates the sound of an engine, whereby sound segments are digitally stored in memory and accessed by a microcontroller which is responsive to a user accessible switch. When the switch is activated and the device is producing an acceleration or deceleration sound, the device will "match" the acceleration or deceleration sound with a closely matched deceleration or acceleration sound, respectively, so that a realistic engine sound is produced.

Abstract: A method and apparatus is capable of accurately deriving acoustic transfer functions such as head-related transfer functions (HRTF) at low cost. Various aspects of the invention include constraining the reflection geometry of a measurement system to facilitate removal of reflection effects, establishing ambient noise level and ambient reverberation time to calibrate test signals, generating soundfields using Golay code test signals, invalidating measurements by detecting test subject movement and short-duration ambient sounds, deriving distance and/or interaural time difference (ITD) using minimum-phase forms of impulse responses, and deriving equalized HRTF suitable for use in acoustic displays without knowing output or input transducer acoustical properties. Spatial resampling of derived HRTF and spectral shaping of test signals are discussed.

Abstract: The object of the present invention is to provide a noise cancelling method and a noise canceller where the shortening of the convergence time and the reduction in the distortion (residual error) after the convergence can be realized.A second adaptive filter outputs a pseudo noise signal by receiving a reference signal from a reference signal input terminal. A subtracter subtracts an output pseudo noise signal of the second adaptive filter from a receiving signal input from a speech signal input terminal, and supplies the subtraction result to the second adaptive filter as an error signal. A divisor circuit divides an output speech signal power of a power averaging circuit obtained from the output error signal of the subtracter by an output noise signal power of another power averaging circuit obtained from the output pseudo noise signal of the second adaptive filter, and outputs the result of the division as an estimated value of the signal to noise ratio (SNR).

Abstract: A matrix decoding system and method generates left, right, center and surround output signals by adding and subtracting weighted versions of first and second input signals. The output signals are generated using a variable matrix to combine the input signals. The variable matrix is controlled by steering control signals derived from a controller which generates the steering control signals responsive to the detected phase difference between the first and second input signals. The decoding system and method uses compressors to generate constant amplitude versions of the input channels prior to performing phase detection. Because the compressors generate constant amplitude signals, phase detection is not affected by an imbalance in channel power.

Abstract: System and method for creating a Doppler Effect signal in a virtual reality environment. A host produces: (1) an audio signal indicative of sound produced by a sound source, (2) a first set of signals indicative of a velocity of the sound source and an observer of the sound source, and (3) a second set of signals indicative of a position of the sound source and the observer. An interpolator interpolates the audio signal and generates an interpolation signal. A Doppler engine receives the first and second sets of signals and generates a decimation factor signal. A decimator filter, receives the interpolation signal and the decimation factor signal and generates a decimation signal. The decimation signal is a digital representation of said Doppler Effect signal and can be converted to an analog signal for broadcast to a listener.

Abstract: An active foam system for noise and vibration control which employs embedded PVDF layers (12) in a urethane foam pad (13). The system can be used to isolate and/or attenuate vibration. It can also be used to cause a reduction in far-field acoustic pressure and to act as a structurally radiated speaker (130).

Abstract: The present invention relates to sound reproduction apparatus comprising stereophonic amplifier means for amplifying left and right signals from any stereo emission source, and a plurality of loudspeakers disposed in two groups, namely one group on the left of a listening direction and another group on the right thereof, each group respectively receiving the amplified left signal and the amplified right signal. The number of said loudspeakers is even and not less than four, the loudspeakers being situated in pairs on axes that are vertical or substantially vertical, with all of the emission faces of said loudspeakers being placed on a surface of continuous curvature, and with the respective vertical and horizontal distances between said loudspeakers being determined as a function of the size of the loudspeakers and as a function of the listening volume.

Abstract: Acoustic feedback is removed from an audio signal (50) by digitizing the audio signal (50) to produce a digitized audio signal (54). The digitized audio signal (54) is then filtered with an adaptive bandpass filter (56) to detect the frequency of the acoustic feedback, where the adaptive bandpass falter (56) is aligned with the feedback based on a phase relationship between the input and the output of the adaptive bandpass filter (56). A notch filter (58) is then configured based on the frequency of the acoustic feedback, and the digitized audio signal (54) is filtered with the notch filter (58) to attenuate the feedback. The feedback-attenuated digitized signal (62) is converted to a feedback-attenuated analog signal (70).

Abstract: A photothermal apparatus is provided for controllably heating and cooling a gas in order to alter and thereby control the acoustic, mechanical or optical properties of the gas. For acoustic applications, the photothermal device may be used to heat and cool the gas in order to generate three-dimensional spatially-located sound corresponding to an electrical audio signal. Also, the photothermal device may be used to generate a three-dimensional sound shield around a noise source in order to prevent the propagation of sound waves from the noise source. It may also be used to controllably heat and cool a gas to thereby provide mechanical energy or force for moving an object.

Abstract: A compatible quadrature type AM sterophobic decoder including an enveolpe detector for providing a current output signal and a combination of a VCA and a synchronous detector for providing a current output signal.The combination of the VCA and the synchronous detector is controlled by a feedback signal from an adder which adds the current output signal of the envelope detector and the inverting current output signal of the conbination of the VCA and the synchronous detector.

Abstract: An active vibration controller includes acceleration detectors for generating output signals on the basis of vibrations of a vehicle, speakers provided in a vehicle's cabin, microphones provided in the vehicle's cabin for receiving generated sounds from the speakers and road noises generated on the basis of running of the vehicle, and adaptive digital filters using output signals from the acceleration detectors as inputs for controlling filter factors on the basis of an RLS algorithm to minimize levels of output signals from the microphones in response to output signals from the microphones and output signals from the acceleration detectors through use of a transfer function matched to the transfer function of the vehicle's cabin in a sound field between the speakers and the microphones. The controller minimized levels of output signals from the microphones by developing an applied output signal to the speakers.

Abstract: An active noise control system is provided with a plurality of error sensor arrays 50,77 which provide signals on lines 64-74,90-100 to beam forming and beam steering logic 76 which cause the arrays 50,77 to exhibit acoustic response profiles 104,106, respectively. The profiles 104,106 intersect in a predefined region 116 to be quieted. The logic 76 provides signals on lines 118, one for each region to be quieted, to active noise control (ANC) logic 20 which also receives inputs from feedforward sensing microphones 10 and provides output signals to acoustic speakers 24 which generate anti-noise 26 to cancel the noise in the quiet region 116. The quiet region 116 may be selectively positioned to any region in the room by steering the beams 104,108. Alternatively, the system may have a plurality of distributed sensors which, when taken together, have an overall maximum (main lobe) acoustic response at a predetermined selectable quiet region.

Abstract: Apparatus for limiting and displaying fader levels employing a display device provided with a linear bar graph display having a plurality of bar graph segments and having an input to which a display signal of variable value can be applied. The display signal has a value range with predetermined maximum and minimum values. The device responds to any value of the display signal to illuminate a corresponding segment. A fader mechanism is manually adjustable to produce a fader signal of variable value. The fader signal has a value range with maximum and minimum values which respectively exceed and fall below the corresponding maximum and minimum values of the display signal. A computer has an input at which the fader signal is applied. The computer stores the maximum and minimum values of the display signal and compares the value of the fader signal with the stored values to produce a display signal.

Abstract: The method for obtaining the quality signal includes multiplying a digital multiplex signal (MPX) by respective reference carrier signals mutually phase shifted by 90.degree. to each other, but otherwise equal, to form a pair of mixed signals (Imr1,Imr2); multiplying the mixed signals (Imr1, Imr2) by respective correction signals (G38c,G38s) to form a pair of corrected mixed signal (Ims1,Ims2); separately multiplying the digital multiplex signal (MPX) by each of two reference pilot signals mutually shifted in phase by 90.degree.

Abstract: According to the invention, sound data is distributed as a plurality of sound data, and the distributed sound data are combined to obtain a plurality of synthesized sound data. The synthesized sound data are sounded by a plurality of speakers, thus forming a sound image. Through combining and multiplexing of sound data in this way, stereo sounds having a sense of spatiality are generated.

Abstract: A photothermal apparatus is provided for controllably heating and cooling a gas in order to alter and thereby control the acoustic, mechanical or optical properties of the gas. For acoustic applications, the photothermal device may be used to heat and cool the gas in order to generate three-dimensional spatially-located sound corresponding to an electrical audio signal. Also, the photothermal device may be used to generate a three-dimensional sound shield around a noise source in order to prevent the propagation of sound waves from the noise source. It may also be used to controllably heat and cool a gas to thereby provide mechanical energy or force for moving an object.

Abstract: An equalizing circuit, for compensating frequency response perturbations in a loudspeaker caused by a recessed mounting of the loudspeaker, includes an input for receiving an audio signal, a peaking network coupled to the input for augmenting the audio signal in a first frequency range, a dipping network also coupled to the input for attenuating the audio signal in a second frequency range, and a combiner for combining an output of the peaking network to an output of the dipping network, an output of the combiner carrying a compensated audio signal for application to the loudspeaker.

Abstract: An engine rotating speed sensor detects intake sound information due to the drive of an engine. A controller generates a signal having a frequency corresponding to a desired ratio of orders based on the detected intake sound information. Further, a phase and an amplitude the signal are controlled, and so a speaker arranged in a propagation path of the intake sound of the engine generates control sound to control the intake sound due to the drive of the engine. An engine noise control apparatus which is capable of effectively reducing or waveform-reshaping a wide range of engine noise. The apparatus has an engine rotating speed sensor for detecting an engine rotating speed and a waveform generator circuit for converting a rotation pulse signal to a periodic signal having a frequency which is a predetermined multiple of the detected engine rotating speed.

Abstract: A method and apparatus for active cancellation of vibrational noise produced by a medical instrument in the head of a patient. Vibrations from the instrument, as well as vibrations in the bone structure in the head of the patient, are sensed and processed to generate cancelling noise waves which are then fed into the inner ear through vibrators placed on the head of the patient. An equalizer shapes the magnitude and phase spectrum of the vibrational signal picked up from the drill and delivers the equalized vibrational signals to the patient. An automatic adaptive controller adjusts the equalizer using control signals consisting of vibrations from the bone structure and the drill.

Abstract: An Audio Signal Processing system in which gain values are calculated for a plurality of output channels so that, from a notional listening position, a notional sound source may be perceived as being positioned anywhere within a notional listening space. First gain contributions arranged to make a predominant contribution when the perceived position is close to the notional listening position are calculated. Second gain contributions arranged to make a predominant contribution when the perceived positions are not close to the notional listening position are calculated. The first gain contributions and the second gain contributions are combined to produce combined gain values for each output channel.