Lucent Technologies Inc.

At&t Bell Laboratories

Mh Acoustics, LLC

At+t Corp.

Robert A Kubli

Gary Wayne Elko

James Edward West

Dennis Raymond Morgan

Jens M Meyer

Gabriel L Miller

Jeffrey Phillip McAteer

James L Flanagan

Eric R Wagner

Ilene J Busch-Vishniac

Daniel A Quinlan

Michael M Goodwin

A microphone array-based audio system that supports representations of auditory scenes using second-order (or higher) harmonic expansions based on the audio signals generated by the microphone array. In one embodiment, a plurality of audio sensors are mounted on the surface of an acoustically rigid sphere. The number and location of the audio sensors on the sphere are designed to enable the audio signals generated by those sensors to be decomposed into a set of eigenbeams having at least one eigenbeam of order two (or higher). Beamforming (e.g., steering, weighting, and summing) can then be applied to the resulting eigenbeam outputs to generate one or more channels of audio signals that can be utilized to accurately render an auditory scene. Alternative embodiments include using shapes other than spheres, using acoustically soft spheres and/or positioning audio sensors in two or more concentric patterns.

Audio system based on at least second-order eigenbeams

In a capacitor microphone system for directional applications, an array of backplates of microphone cells are formed on a printed circuit (PC) board. A continuous strip of diaphragm is employed to cover each backplate. The diaphragm is stretched to create a uniform tension along its length, contributing to the objective of achieving a uniform gain by each microphone cell. In addition, the diaphragm is separated from the backplates by a relatively large distance such that the percentage deviation from such a distance from cell to cell is relatively small, again contributing to the objective of gain uniformity.

Directional capacitor microphone system

An acoustic signal receiving apparatus comprising a housing having an acoustically reflecting surface and a directional acoustic sensor unit having first-order gradient characteristics. The sensor unit is coupled to the housing with use of a retractable member having a retracted position and an extended position. When the member is extended, the sensor unit is positioned relative to the reflecting surface such that the acoustic interaction between the sensor unit and the reflecting surface causes the output of the sensor unit to have second-order gradient response characteristics. In accordance with one illustrative embodiment, in a notebook computer with a 'flip-back' lid, the sensor element automatically extends to the desired position when the lid is opened, and automatically retracts to be flush with the housing surface when the lid is closed.

Collapsible image derived differential microphone

Method and apparatus for the active cancellation of broad band noise and/or single frequency tones emanating from rotating machinery, such as an air moving device, by detecting related mechanical and acoustic signals therein and causing canceling vibrations to be applied directly to the rotating machinery by a transducer.

Apparatus and method for the active control of air moving device noise

A method and apparatus for providing a differential microphone with a desired frequency response are disclosed. The desired frequency response is provided by operation of a filter, having an adjustable frequency response, coupled to the microphone. The frequency response of the filter is set by operation of a controller, also coupled to the microphone, based on signals received from the microphone. The desired frequency response may be determined based upon the distance between the microphone and a source of sound, and may comprise both a relative frequency response and absolute output level. The frequency response of the filter may comprise the substantial inverse of the frequency response of the microphone to provide a flat response. Furthermore, the filter may comprise a Butterworth filter.

Adjustable filter for differential microphones

An electret transducer array and fabrication technique are disclosed. The array comprises a foil having a layer of insulating material and a layer of metal in contact therewith. The layer of metal comprises one or more discrete areas of metal which define the active areas of one or more transducers in the array. Electrical leads are coupled to the discrete areas of metal. By means of these leads, electrical signals produced by each transducer in response to incident acoustic signals may be accessed. The areas of metal may be formed by selectively removing metal from the foil, or by selective metal deposition. The layer of insulating material is electrostatically charged. The electret transducer array further comprises a porous backplate of sintered metal. The backplate further comprises a rough surface in contact with the layer of insulating material. The backplate serves as a common electrode for transducers of the array. A second backplate is provided positioned adjacent to the metal layer of the foil forming an air gap therewith. The second backplate provides, among other things, shielding from stray electromagnetic fields.

Electret transducer array and fabrication technique

Second-order gradient (SOG) toroidal and unidirectional microphones derived using a first-order gradient sensor (FOG) and a reflecting plane are described. The FOG is positioned with its axis illustratively orthogonal to and suspended a few centimeters from a large acoustically reflecting surface. The resulting sensor image is phase reversed resulting in a transducer that is a linear quadrupole. The linear quadrupole can be described by two dimensions, the distance corresponding to the FOG's dipole distance and twice the distance from the reflecting plane. If the reflecting surface is large enough or if the wall of an enclosure is used, the resulting microphone becomes a SOG unidirectional microphone. The perfect match between the sensor and its image from a good acoustic reflector results in an ideal SOG microphone with 3 dB beam width of .+-.33.degree. and no grating lobes below about 3 kHz for a spacing from the reflecting plane of about 2.5 cm. A wall-mounted toroid can be formed by using two FOGs at right angles to each other and with the axis of each sensor at 45.degree. to the reflecting surface and a spacing between transducers that is twice the height of the transducers from the reflecting plane. A table-mounted toroid can be realized by properly combining a filtered version of a suspended FOG and an omnidirectional sensor flush mounted to the reflecting table-top. Other arrays of image-derived directional sensors are applied to hands-free telephoning and other noise and reverberation-reducing arrangements.

Image derived directional microphones

A back electrode has a plurality of ridges on one surface. An electret foil is spaced from the ridged surface of the back electrode. In the absence of applied pressure, a gap remains between the foil and the surface of the back electrode between the ridges. Above one applied pressure, the foil collapses between the ridges. Below a second applied pressure, the foil returns to its original position.

Electret transducer for blood pressure measurement

A directional acoustic transducer includes a plurality of acoustic paths each having first and second ends. The second end of each path terminates in the atmosphere. An electroacoustic device is attached to an acoustic cavity and the acoustic path first ends are coupled to the said acoustic cavity through an acoustic arrangement adapted to produce a predetermined transducer directional response pattern.

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Milford, NJ, United States of America

Robert A Kubli