Granted Patent B2

US 8,199,928 · App. 12/118,205 · Granted Jun 12, 2012

Abstract

Claims (27)

1. A method for processing an acoustic input signal to provide an output signal with reduced noise, the method comprising:

weighting the input signal using a frequency-dependent weighting function, where the weighting function is bounded below by a frequency-dependent threshold function, and wherein the weighting function represents whichever is the greater of:

i. one minus a product of a noise overestimation factor times a ratio of an estimated power density spectrum of a noise component of the input signal to an estimated power density spectrum of the input signal, and

ii. the threshold function.

2. The method of claim 1 , where the threshold function comprises a time-dependent function.

3. The method of claim 1 further comprising:

attempting to detect a presence of a wanted signal; and

if no such wanted signal is detected, adapting the weighting function.

4. The method of claim 1 , where the threshold function is based on a target noise spectrum.

5. The method of claim 4 , where the target noise spectrum comprises a time-dependent target noise spectrum.

6. The method of claim 4 , further comprising:

attempting to detect a presence of a wanted signal detection; and

if no such wanted signal is detected, adapting the target noise spectrum.

7. The method of claim 6 , where if power of the target noise spectrum at time (n−1) within a predetermined frequency interval is smaller than a predetermined attenuation factor times an estimate of the power of a noise component in the input signal at time n within the predetermined frequency interval, then the target noise spectrum at time n is incremented.

8. The method of claim 4 , where the threshold function is based on the lesser of:

i. a predetermined minimum attenuation value, and

ii, a quotient of the target noise spectrum and the absolute value of the input signal.

9. The method of claim 4 , where the threshold function is based on at least two target noise spectra.

10. A computer program product comprising:

a memory; and

weighting logic stored in the memory and operable to weight an input signal using a frequency-dependent weighting function, where the weighting function is bounded below by a frequency-dependent threshold function, and wherein the weighting function represents whichever is the greater of:

i. one minus a product of a noise overestimation factor times a ratio of an estimated power density spectrum of a noise component of the input signal to an estimated power density spectrum of the input signal, and

ii. the threshold function.

11. An apparatus for processing an acoustic input signal to provide an output signal with reduced noise, comprising:

a processor operable to weight the input signal using a frequency dependent weighting function, where the weighting function is bounded below by a frequency dependent threshold function, and wherein the weighting function represents whichever is the greater of:

i. one minus a product of a noise overestimation factor times a ratio of an estimated power density spectrum of a noise component of the input signal to an estimated power density spectrum of the input signal, and

ii. the threshold function.

Assignments (13)