Telephonic handset employing feed-forward noise cancellation
First Claim
1. A telephonic handset comprising an active noise reduction (ANR) system, wherein:
- the ANR system comprises a noise reference microphone and a digital filter;
the digital filter is receivingly coupled to the noise reference microphone, and transmittingly coupled to a receiver transducing element in the handset;
the digital filter is a non-adaptive IIR filter; and
the ANR system is configured as a fixed feed-forward noise-cancellation system.
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Abstract
A telephonic handset comprises an active noise reduction (ANR) system. The ANR system comprises a reference microphone and an IIR filter. The IIR filter is receivingly coupled to the reference microphone with respect to noise reference signals, and it is transmittingly coupled to the receiver transducing element of the handset. The ANR system is configured as a fixed feed-forward noise cancellation system. Preferably, the IIR filter has a transfer function derived, in part, from the open-loop gain of a feedback noise cancellation system.
In specific embodiments of the invention, the noise reference microphone is situated so as to sample the ambient noise field near the front face of the receiver, but without directly sampling the noise field on the front face.
52 Citations
19 Claims
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1. A telephonic handset comprising an active noise reduction (ANR) system, wherein:
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the ANR system comprises a noise reference microphone and a digital filter; the digital filter is receivingly coupled to the noise reference microphone, and transmittingly coupled to a receiver transducing element in the handset; the digital filter is a non-adaptive IIR filter; and the ANR system is configured as a fixed feed-forward noise-cancellation system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of active noise reduction (ANR), comprising:
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sampling ambient noise adjacent an external surface of a telephonic handset, thereby to provide a reference signal; processing the reference signal in a non-adaptive IIR filter, thereby to provide a cancellation signal effective for at least partially canceling ambient noise in the vicinity of the entrance to a user'"'"'s ear canal; and feeding the cancellation signal forward to a receiver transducing element substantially without feedback from said element. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A telephonic handset comprising:
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a noise reference microphone configured to sample a noise field at a sampling location and to generate a noise signal in response to the noise field; a receiver transducing element; a non-adaptive digital IIR filter configured to process the noise signal, thereby to form a noise-cancelling signal; and circuitry configured to combine the noise-cancelling signal with a far-end speech signal and to forward the combined signals to the receiver transducing element; wherein the IIR filter is configured in a fixed feed-forward noise-cancellation system.
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Specification