Frequency control based on device properties
View Patent ↗There is provided a method of controlling a noise cancellation system, the noise cancellation system being for use in a device comprising a speaker for receiving a wanted signal and generating a sound signal therefrom, and the noise cancellation system comprising: a digital filter, for generating a noise cancellation signal from an input signal representative of ambient noise; and an output for applying the noise cancellation signal to the speaker in addition to the wanted signal to generate a sound signal from which the ambient noise has been at least partially cancelled. The method comprises: determining a resonant frequency of the speaker; based on the determined resonant frequency, selecting a set of filter coefficients; and applying the selected set of filter coefficients to the digital filter.
1. A method of controlling a noise cancellation system, the noise cancellation system being for use in a device comprising a speaker for receiving a wanted signal and generating a sound signal therefrom, and the noise cancellation system comprising: a digital filter, for generating a noise cancellation signal from an input signal representative of ambient noise; and
an output for applying the noise cancellation signal to the speaker in addition to the wanted signal to generate a sound signal from which the ambient noise has been at least partially cancelled,
the method comprising:
determining a resonant frequency of the speaker;
in response to the determination of the resonant frequency, selecting a set of filter coefficients from a plurality of prestored sets of filter coefficients; and
applying the selected set of filter coefficients to the digital filter.
2. A method as claimed in claim 1 , wherein the step of determining the resonant frequency of the speaker comprises determining said resonant frequency from a plurality of predetermined frequencies.
3. A method as claimed in claim 2 , wherein the plurality of prestored sets of filter coefficients comprise one prestored set of filter coefficients corresponding to each of said plurality of predetermined frequencies.
4. A method as claimed in claim 2 , wherein the step of determining the resonant frequency comprises applying signals to the speaker at each of said predetermined frequencies, and detecting a resulting current.
5. A method as claimed in claim 4 , comprising applying to the speaker a composite signal containing components at each of said predetermined frequencies, and using a digital Fourier transform to detect resulting currents at each of said predetermined frequencies.
6. A method as claimed in claim 1 , comprising determining the resonant frequency of the speaker at a time when the speaker has been receiving a signal.
7. A method as claimed in claim 2 , wherein the step of determining the resonant frequency of the speaker comprises detecting currents at each of said predetermined frequencies, resulting from application of a voice or noise cancellation signal to the speaker.
8. A noise cancellation system, for use in a device comprising a speaker for receiving a wanted signal and generating a sound signal therefrom, the noise cancellation system comprising:
a digital filter, for generating a noise cancellation signal from an input signal representative of ambient noise; and
an output for applying the noise cancellation signal to the speaker in addition to the wanted signal to generate a sound signal from which the ambient noise has been at least partially cancelled,
wherein the noise cancellation system is adapted to:
determine a resonant frequency of the speaker;
in response to the determination of the resonant frequency, select a set of filter coefficients from a plurality of prestored sets of filter coefficients; and
apply the selected set of filter coefficients to the digital filter.
9. A method as claimed in 1 , wherein the step of determining the resonant frequency of the speaker comprises determining said resonant frequency from a plurality of predetermined frequencies.
10. A noise cancellation system as claimed in claim 8 , adapted to determine the resonant frequency of the speaker by determining said resonant frequency from a plurality of predetermined frequencies.
11. A noise cancellation system as claimed in claim 10 , wherein the plurality of prestored sets of filter coefficients comprise one prestored set of filter coefficients corresponding to each of said plurality of predetermined frequencies.
12. A noise cancellation system as claimed in claim 10 , adapted to determine the resonant frequency by applying signals to the speaker at each of said predetermined frequencies, and detecting a resulting current.
13. A noise cancellation system as claimed in claim 12 , adapted to apply to the speaker a composite signal containing components at each of said predetermined frequencies, and adapted to use a digital Fourier transform to detect resulting currents at each of said predetermined frequencies.
14. A noise cancellation system as claimed in claim 8 , adapted to determine the resonant frequency of the speaker at a time when the speaker has been receiving a signal.
15. A noise cancellation system as claimed in claim 10 , adapted to determine the resonant frequency of the speaker by detecting currents at each of said predetermined frequencies, resulting from application of a voice or noise cancellation signal to the speaker.
16. A noise cancellation system as claimed in claim 8 , adapted to determine the resonant frequency of the speaker by determining said resonant frequency from a plurality of predetermined frequencies.
17. An integrated circuit, comprising:
a noise cancellation system according to claim 8 .
18. A mobile phone, comprising:
an integrated circuit as claimed in claim 17 .
19. A pair of headphones, comprising:
an integrated circuit as claimed in claim 17 .
20. A pair of earphones, comprising:
an integrated circuit as claimed in claim 17 .
21. A headset, comprising:
an integrated circuit as claimed in claim 17 .