Abstract: A method or system is provided for real-time synthesis in a rehearsal space of an acoustic environment of a target space. Microphones, pick-ups or other devices are used to separately record the singing or instruments. These “dry” instrument signals are sent to a remote site, where they are processed to imprint the acoustics of the desired location. Performers in a rehearsal space with loudspeakers are close-miked. The signals collected would be sent to a processing center via a low-latency internet connection, where the signals would be processed according to the response of the target acoustic space, corrected by the known acoustics and loudspeaker configuration of the rehearsal space. The processed signals would then be sent back to the rehearsal space, where they would be amplified and played over the loudspeakers, thereby giving the impression that the performers are performing in the target acoustic space.

Abstract: The present invention relates to methods and apparatuses for using head waves to greatly improve microseismic event localization accuracy, particularly in the depth dimension, by analyzing them in addition to direct path arrivals whenever they are observed. Embodiments of the invention also include techniques known as multipath analysis.

Abstract: According certain aspects, embodiments of the invention consider the problem of microseismic event localization from a parameter estimation perspective, and include a method and system for computing and displaying characteristics of event localization errors. According to certain other aspects, embodiments of the invention include techniques for deriving aggregate statistics from a set of event location estimates, including methods for computing and displaying the probability that an event occurred in any given volume, and methods for describing and displaying the smallest volume that contains a specified percentage of the event probability or expected to contain the specified percentage of the events.

Abstract: The present invention relates to audio signal processing, and more particularly to methods and apparatuses for emulating and controlling various features of mechanical spring reverberation in a digital audio processing system. According to certain aspects of the invention, such an emulation is performed so as to enhance or alter the characteristics of a digitally stored or processed audio signal in substantially the same manner as a mechanical spring reverberation system. In one example embodiment, the propagation of energy through a mechanical spring is simulated using dispersive waveguides, wherein left-going and right-going waves are separately processed, and the effects of dispersion and attenuation commuted to the waveguide ends. According to additional aspects, many spring reverberators contain spring elements arranged in parallel, with no coupling between springs.

Abstract: A system and method for graphic equalization of audio signals is disclosed. Traditional graphic equalizers provide control over the gains in each of a set of frequency bands. However, the actual band gains vary from the desired gains due to crosstalk between bands. Prior art methods for addressing this difficulty include applying a correction filter to the equalizer, and adjusting the shape of the individual band filters, both of which increase the computational cost. In an embodiment of the present invention, the input gains are processed to produce a set of adjusted gains which take into account the crosstalk, and result in an equalization interpolating the input band gains.

Abstract: A method and system for designing a discrete-time filter having a transfer function which approximates that of an analog shelf filter is disclosed. Prior art methods include applying the bilinear transform to the analog filter, which has the drawback of warping high-frequency features of the desired transfer function. In an embodiment of the present invention, an analog filter is designed which anticipates the warping imposed by the bilinear transform. For filters whose features approach the Nyquist limit, the inventive method provides a closer approximation to the analog response than direct application of the bilinear transform.

Abstract: The invention is a crosstalk canceler wherein different frequency bands are canceled at different locations so as to allow greater listener movement about the “sweet spot” while maintaining effective crosstalk cancellation. A spectrally smooth canceler equalization is used, reducing artifacts for listeners away from the sweet spot and further enlarging the sweet spot. Finally, the canceler equalization is adapted to either the anticipated or the actual crosscoherence among the input channels, producing a natural equalization regardless of the input.

Abstract: The invention is a crosstalk canceler wherein different frequency bands are canceled at different locations so as to allow greater listener movement about the “sweet spot” while maintaining effective crosstalk cancellation. A spectrally smooth canceler equalization is used, reducing artifacts for listeners away from the sweet spot and further enlarging the sweet spot. Finally, the canceler equalization is adapted to either the anticipated or the actual crosscoherence among the input channels, producing a natural equalization regardless of the input.

Abstract: A crosstalk canceler wherein different frequency bands are canceled at different locations so as to allow greater listener movement about the “sweet spot” while maintaining effective crosstalk cancellation. A spectrally smooth canceler equalization is used, reducing artifacts for listeners away from the sweet spot and further enlarging the sweet spot. Finally, the canceler equalization is adapted to either the anticipated or the actual crosscoherence among the input channels, producing a natural equalization regardless of the input.

Abstract: A method and apparatus implements a novel surround sound panning paradigm. Rather than controlling the x-y position of a perceived sound source within a linear grid, the perceived sound is characterized by specifying perceived arrival energy as a function of direction of arrival. In one embodiment, perceived sound source azimuth and width (or spatial extent) are specified, which parameters are used in a novel panning law to control each output channel. In a preferred implementation, the panning control is provided in a Plug-In application for a conventional DAW environment such as Pro Tools, which application includes an interface that provides precise control over the direction and spatial extent of audio.

Abstract: A three-dimensional virtual audio display method is described which includes generating a set of transfer function parameters in response to a spatial location or direction signal. An audio signal is filtered in response to the set of transfer function parameters. The set of transfer function parameters are selected from or interpolated among parameters derived by smoothing frequency components of a known transfer function over a bandwidth which is a non-constant function of frequency. The smoothing includes for each frequency component in at least part of the audio band of the display, applying a mean function to the amplitude of the frequency components within the bandwidth containing the frequency component, and noting the parameters of the resulting compressed transfer function.

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: A method and apparatus for processing data from a positioning or navigation system, such as global positioning system (GPS) navigation system data. In preferred embodiments, the invention is a method and apparatus for estimating position based on GPS measurements and optionally, measurements from other types of navigation sensors combined with GPS navigation system data. The apparatus of the invention includes a point position estimator (which preferably approximates a maximum likelihood estimator) for processing data from a positioning or navigation system to generate point position estimate data, and a smoothing filter for smoothing the point position estimate data. The smoothing filter can be a linear Kalman filter.

Abstract: A three-dimensional virtual audio display method is described which includes generating a set of transfer function parameters in response to a spatial location or direction signal. An audio signal is filtered in response to the set of transfer function parameters. The set of transfer function parameters are selected from or interpolatated among parameters derived by smoothing frequency components of a known transfer function over a bandwidth which is a non-constant function of frequency. The smoothing includes for each frequency component in at least part of the audio band of the display, applying a mean function to the amplitude of the frequency components within the bandwidth containing the frequency component, and noting the parameters of the resulting compressed transfer function.

Abstract: Spatialization of soundfields is accomplished by filtering audio signals using filters having unvarying frequency response characteristics and amplifying signals using amplifier gains adapted in response to signals representing sound source location and/or listener position. The filters are derived using a singular value decomposition process which finds the best set of component impulse responses to approximate a given set of head related transfer functions. Efficient implementations for rendering reflection effects, and for spatializing multiple sound sources and/or generating multiple output signals are disclosed.

Abstract: A method and apparatus for processing a set of signals to identify narrow bandwidth features of the signals, and optionally to process the signals further to extract information about the identified narrow-band features. The invention processes a set of input signal frames (a multi-dimensional pixel array) to generate a narrow-band feature signal (also a multi-dimensional pixel array) from which narrow-band features of the input signal frames can be efficiently, automatically, and unambiguously identified. In a class of preferred embodiments, the input signal frames are the power spectra of a set of sequentially measured signals. Thus, the set of input signal frames is a "spectrogram," comprising rows and columns of pixels (with row indices representing time, and column indices representing frequency). Alternatively, the input signal frames represent a data array of another type, such as a correlogram or a sequence of images.

Abstract: The restoration of a band-limited signal which has undergone amplitude clipping is viewed as recovery from signal drop-outs (missing samples over an interval of time), with the extrapolated signal constrained to lie outside the clipping interval during the drop out. If the signal is oversampled, and the clipping threshold moderate, a unique reconstruction may result from application of signal matching and bandwidth constraints. More generally, however, candidate reconstructions are seen to lie on or inside a polyhedron in the space of sampled signals. In contrast to the case of extrapolation through missing samples, upper and lower limits typically can be placed on the reconstructed signal at every sample point. In light of this finding, methods for choosing a unique reconstruction are achieved. The use of inequality constraints allows practical restoration of clipped signals.

Abstract: A method and apparatus for processing a set of signals to identify narrow bandwidth features of the signals, and optionally to process the signals further to extract information about the identified narrow-band features. The invention processes a set of input signal frames (a two-dimensional pixel array) to generate a narrow-band feature signal (also a two-dimensional pixel array) from which narrow-band features of the input signal frames can be efficiently, automatically, and unambiguously identified. In a class of preferred embodiments, the input signal frames are the power spectra of a set of sequentially measured signals. Thus, the set of input signal frames is a "spectrogram," comprising rows and columns of pixels (with row indices representing time, and column indices representing frequency). Alternatively, the input signal frames represent a data array of another type, such as a correlogram or a sequence of images.

Abstract: Conductive materials are formed by implanting high energy ions (30 keV to 300 keV) into rigid backboned polymers, such as poly (p-phenylene sulfide); conductivities on the order of 10.sup.-3 (ohm-cm).sup.-1 are demonstrated and the materials remain stable over periods as long as a year.