Noise cancellation
AssigneeCirrus Logic International Semiconductor Ltd.
InventorRichard Clemow
Life of this patent
Estimating the term…
Abstract
A noise cancellation signal is generated by generating an ambient noise signal, representing ambient noise, and generating a noise cancellation signal, by applying the ambient noise signal to an feedforward filter, where the feedforward filter comprises a high-pass filter having an adjustable cut-off frequency, and by applying a controllable gain. The noise cancellation signal is then applied to a loudspeaker, to generate a sound to at least partially cancel the ambient noise. An error signal is generated, representing unwanted sound in the region of the loudspeaker. The phase of the ambient noise signal is compared to a phase of the error signal, and the gain is controlled on the basis of a result of the comparison, taking account of a phase shift introduced by the high-pass filter when performing the comparison.
Claims17
A method for correcting a gain of a noise cancellation system, the method comprising:
- generating an ambient noise signal, representing ambient noise;
- generating a noise cancellation signal, by applying the ambient noise signal to a feedforward filter, wherein the feedforward filter comprises a high-pass filter having an adjustable cut-off frequency, and by applying a controllable gain;
- applying the noise cancellation signal to a loudspeaker, to generate a sound to at least partially cancel the ambient noise;
- and
- generating an error signal, representing unwanted sound in the region of the loudspeaker, wherein the method further comprises:
- comparing a phase of the ambient noise signal to a phase of the error signal, and controlling said gain on the basis of a result of said comparison, and taking into consideration any changes to the phase of the noise cancellation signal when controlling said gain.
A computer program product, comprising code for causing a computer to perform a method for correcting a gain of a noise cancellation system, the method comprising:
- receiving an ambient noise signal, representing ambient noise;
- generating a noise cancellation signal by applying the ambient noise signal to a feedforward filter, wherein the feedforward filter comprises a high-pass filter having an adjustable cut-off frequency, and by applying a controllable gain;
- applying the noise cancellation signal to a loudspeaker, to generate a sound to at least partially cancel the ambient noise;
- and
- generating an error signal, representing unwanted sound in the region of the loudspeaker, wherein the method further comprises:
- comparing a phase of the ambient noise signal to a phase of the error signal, and controlling said gain on the basis of a result of said comparison, and taking into consideration any changes to the phase of the noise cancellation signal when controlling said gain.
A sound reproduction device, comprising a noise cancellation system, wherein the noise cancellation system is adapted to:
- receive an ambient noise signal, representing ambient noise;
- generate a noise cancellation signal by applying the ambient noise signal to a feedforward filter, wherein the feedforward filter comprises a high-pass filter having an adjustable cut-off frequency, and by applying a controllable gain;
- apply the noise cancellation signal to a loudspeaker, to generate a sound to at least partially cancel the ambient noise;
- and
- generate an error signal, representing unwanted sound in the region of the loudspeaker, wherein the noise cancellation system is further adapted to:
- compare a phase of the ambient noise signal to a phase of the error signal, and control said gain on the basis of a result of said comparison, and taking into consideration any changes to the phase of the noise cancellation signal when controlling said gain.
Dependencies are inferred from the claim text.