Communications – electrical: acoustic wave systems and devices – Distance or direction finding
Reexamination Certificate
1998-12-23
2001-02-06
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
Reexamination Certificate
active
06185152
ABSTRACT:
FIELD
This invention relates generally to sound steering systems and, in particular the present invention relates to a spatial sound steering system utilizing three-dimensional spatial audio technology.
BACKGROUND
Many systems have been proposed which can detect a signal from a sound source for a variety of different purposes. Videoconferencing systems and other communication systems, as well as various types of security, automation and monitoring systems are used to enhance, simplify or safeguard lives. More advanced sound-detecting systems also make it possible to determine the direction or location of the sound source using voice-directional camera image steering. In U.S. Pat. No. 5,778,082 to Chu et al., for example, a system and method for localization of an acoustic source is described using a pair of spatially separated microphones to obtain direction or location of speech or other acoustic signals from a common sound source. Similarly, U.S. Pat. No. 5,686,957 to Baker uses an array of microphones to determine the direction of a particular human speaker in a hemispheric viewing area, and to provide directional signals to a video camera system. However, since the Chu and Baker systems, as well as other similar systems can only detect the “differences” in audio signal amplitude, two or microphones must be used to determine directionality of a sound source, thus increasing the cost and complexity of these systems.
U.S. Pat. No. 5,742,693 to Elko discloses an acoustic transducer comprising a finite acoustical reflecting surface or baffle having one or more sensors to produce a first or second-order differential response pattern at a predetermined frequency. The sensors in Elko are image-derived sensors which must be positioned on the baffle itself. Furthermore, the transducer in Elko requires the baffle to be about one to one-half of an acoustic wavelength at a predetermined frequency. Such limitations make it difficult to use the device in Elko with standard videoconferencing equipment, such as video cameras.
For the reasons stated above, there is a need in the art for a more convenient and compact system for detecting the directionality of a sound source.
SUMMARY
An apparatus and method for determining directionality of acoustic signals arriving from an acoustic source is disclosed. A plurality of reflectors for modifying the acoustic signals and a transducer located proximate to the reflectors is used. A notch detector detects and identifies spectral notches in the modified acoustic signals. A device then determines the direction of the acoustic source.
In one embodiment, a microphone system capable of detecting three-dimensional sound is provided. The microphone system comprises an elliptical-shaped microphone enhancer having at least two reflectors located different distances apart from a microphone located in the center of the ellipse. The reflectors have asymmetric ridges which cause interference patterns in the signals received by the microphone, conceptually analogous to the patterns generated by the pinnae of the human ear.
In another embodiment, a sound steering system is disclosed which utilizes the directional information to guide a camera towards a sound source. Unlike conventional videoconferencing systems which use specialized imaging equipment, or require at least two microphones to determine directionality, the sound steering system of the present invention requires only one microphone and can be integrated with conventional videoconferencing equipment.
In another embodiment, an analog signal from the microphone system is converted into separate frames of time-based digital audio information. Fourier analysis is used to convert this time-based information into frequency-based spectral coefficients. A spatial estimator then uses the spectral coefficients to find spectral notches or anti-resonances within frames. The spatial estimator associates these frames with known spatial coordinates using a look-up table and conveys this information to the camera motor.
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Intel Corporation
Pihulic Daniel T.
Schwegman Lundberg Woessner & Kluth P.A.
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