Open Air Noise Cancellation
First Claim
1. An apparatus for actively cancelling an ambient sound wavefront in an open air environment, the apparatus comprising:
- a directional microphone having a first polar response, the directional microphone configured to, in response to a portion of the ambient sound wavefront being incident upon the directional microphone, produce a microphone output signal representative of the portion of the ambient sound wavefront;
a directional loudspeaker having a second polar response, the directional loudspeaker positioned behind the microphone such that the first polar response and the second polar response are opposite in orientation; and
a signal processing module configured to receive the microphone output signal from the directional microphone and transmit a control signal to the directional loudspeaker, the control signal causing the directional loudspeaker to produce a noise cancellation wavefront, wherein the noise cancellation wavefront and the ambient sound wave are equal in magnitude and inverse in polarity.
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Abstract
An active noise cancellation device is described that is capable of cancelling an ambient sound wave in an open air environment via destructive interference. The active noise cancellation device comprises a directional microphone, a directional loudspeaker, and a signal processing module. The directional loudspeaker can comprise either one or two dipole loudspeakers in combination with a sealed loudspeaker. Multiple active noise cancellation devices can be arranged in arrays to create open air active noise cancellation systems. Each active noise cancellation device within the array, when combined with the outputs of the other devices within the array, produces a noise cancellation wavefront that actively cancels a portion of an ambient sound wavefront. Arrays of any geometry or spatial dimension are possible.
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Citations
22 Claims
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1. An apparatus for actively cancelling an ambient sound wavefront in an open air environment, the apparatus comprising:
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a directional microphone having a first polar response, the directional microphone configured to, in response to a portion of the ambient sound wavefront being incident upon the directional microphone, produce a microphone output signal representative of the portion of the ambient sound wavefront; a directional loudspeaker having a second polar response, the directional loudspeaker positioned behind the microphone such that the first polar response and the second polar response are opposite in orientation; and a signal processing module configured to receive the microphone output signal from the directional microphone and transmit a control signal to the directional loudspeaker, the control signal causing the directional loudspeaker to produce a noise cancellation wavefront, wherein the noise cancellation wavefront and the ambient sound wave are equal in magnitude and inverse in polarity. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for actively cancelling an ambient sound wavefront in an open air environment, the system comprising:
a plurality of noise cancellation devices arranged in an array, wherein each noise cancellation device comprises; a directional microphone having a first polar response, the directional microphone configured to, in response to a portion of the ambient sound wavefront being incident upon the directional microphone, produce a microphone output signal representative of the portion of the ambient sound wavefront; a directional loudspeaker having a second polar response, the directional loudspeaker positioned behind the microphone such that the first polar response and the second polar response are opposite in orientation; and a signal processing module configured to receive the microphone output signal from the directional microphone and to transmit a control signal to the directional loudspeaker such that the directional loudspeaker produces a noise cancellation wavefront, wherein the noise cancellation wavefront and the ambient sound wavefront are equal in magnitude and inverse in polarity. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
Specification