Method and apparatus for suppressing wind noise
The invention includes a method, apparatus, and computer program to selectively suppress wind noise while preserving narrow-band signals in acoustic data. Sound from one or several microphones is digitized into binary data. A time-frequency transform is applied to the data to produce a series of spectra. The spectra are analyzed to detect the presence of wind noise and narrow band signals. Wind noise is selectively suppressed while preserving the narrow band signals. The narrow band signal is interpolated through the times and frequencies when it is masked by the wind noise. A time series is then synthesized from the signal spectral estimate that can be listened to. This invention overcomes prior art limitations that require more than one microphone and an independent measurement of wind speed. Its application results in good-quality speech from data severely degraded by wind noise.
1. A method for attenuating noise in a signal detected by a sound detector device, comprising:
receiving separately by the sound detector device, at least a first signal and a second signal, wherein the first signal and the second signal being uncorrelated to each other both in phase and in amplitude;
performing separately, a time-frequency transform on the first signal and the second signal to obtain respective transformed data, wherein the first signal and the second signal remain uncorrelated to each other both in phase and in amplitude when respectively being time-frequency transformed;
performing signal analysis on the respective transformed data, by a processor, to identify wind noise in the respective transformed data that is caused by wind pressure fluctuations associated with wind striking a portion of the sound detector device;
identifying the wind noise by detecting a difference of both the amplitude and the phase between a plurality of signal peaks that comprise the respective transformed data that exceed an amplitude threshold and a phase threshold, respectively to identify the wind noise; and
attenuating at least a portion of the wind noise identified in the respective transformed data.
2. The method of claim 1 , where the step of performing signal analysis further comprises:
analyzing features of a spectrum of the respective transformed data;
assigning evidence weights based on the step of analyzing; and
processing the evidence weights to determine whether wind noise is present in the spectrum of the respective transformed data.
3. The method of claim 1 , where the step of performing signal analysis further comprises identifying peaks in a spectrum of the respective transformed data that have a Signal to Noise Ratio (SNR) exceeding a peak threshold as peaks not stemming from wind noise.
4. The method of claim 1 , where the step of performing signal analysis further comprises identifying peaks in a spectrum of the respective transformed data that are sharper and narrower than a selected criterion as peaks stemming from a signal of interest.
5. The method of claim 4 , where the step of identifying comprises measuring peak widths by taking an average difference between a highest point and its neighboring points on each side.
6. The method of claim 1 , where the step of performing signal analysis further comprises:
determining a stability of peaks by comparing peaks in a current spectra of the respective transformed data to peaks from a previous spectra of the respective transformed data; and identifying stable peaks as peaks not stemming from wind noise.
7. The method of claim 1 , where the step of performing signal analysis further comprises:
determining differences in phase and amplitude of peaks from signals from a plurality of microphones; and
identifying peaks whose phase and amplitude differences exceed a difference threshold as peaks stemming from wind noise.
8. The method of claim 1 , where the step of performing signal analysis further comprises: fitting a single straight line to a portion of a spectrum of the respective transformed data;
comparing a slope of the single straight line to a pre-defined threshold; and
determining whether wind noise is present in the spectrum of the respective transformed data from the slope.
9. The method of claim 1 , where the step of performing signal analysis further comprises:
fitting a single straight line to a portion of a spectrum of the respective transformed data;
comparing an intersection point of the single straight line to a pre-defined threshold; and
determining whether wind noise is present in the spectrum of the respective transformed data from the intersection point.
10. An apparatus for suppressing noise, comprising:
at least a first sound detector device and a second sound detector device configured to separately receive at least a first signal and a second signal, wherein the first signal and the second signal being uncorrelated to each other both in phase and in amplitude;
a time-frequency transform component configured to separately transform the first signal and the second signal to obtain respective time-based signals to respective frequency-based data, wherein the first signal and the second signal remain uncorrelated to each other both in phase and in amplitude when respectively being time-frequency transformed;
a signal analyzer configured to identify wind noise in the respective frequency-based data that is caused by wind pressure fluctuations associated with wind striking a portion of the first sound detector device and the second sound detector device that detected the respective time-based signals, wherein the signal analyzer identifies the wind noise by detecting a difference of both the amplitude and the phase between a plurality of signal peaks that comprise the respective transformed data that exceed an amplitude threshold and a phase threshold, respectively to identify the wind noise; and
a wind noise attenuation component configured to attenuate at least a portion of the wind noise in the respective frequency-based data using results obtained from the signal analyzer.
11. The apparatus of claim 10 , where the signal analyzer is configured to:
analyze features of a spectrum of the respective frequency-based data;
assigning evidence weights based on the step of analyzing; and
processing the evidence weights to determine whether wind noise is present in the spectrum of the respective frequency-based data.
12. The apparatus of claim 10 , where the signal analyzer is configured to identify peaks in a spectrum of the respective frequency-based data that have a Signal to Noise Ratio (SNR) exceeding a peak threshold as peaks not stemming from wind noise.
13. The apparatus of claim 10 , where the signal analyzer is configured to identify peaks in a spectrum of the respective frequency-based data that are sharper and narrower than a selected criterion as peaks stemming from a signal of interest.
14. The apparatus of claim 13 , where the signal analyzer is configured to measure peak widths by taking an average difference between a highest point and its neighboring points on each side.
15. The apparatus of claim 10 , where the signal analyzer is configured to: determine a stability of peaks by comparing peaks in a current spectra of the respective frequency-based data to peaks from a previous spectra of the respective frequency-based data; and
identify stable peaks as peaks not stemming from wind noise.
16. The apparatus of claim 10 , where the signal analyzer is configured to:
determine differences in the phase and the amplitude of peaks from the first and the second signals from a plurality of microphones; and
identify peaks whose phase and amplitude differences exceed a difference threshold as peaks stemming from wind noise.
17. The apparatus of claim 10 , where the signal analyzer is configured to:
fit a single straight line to a portion of a spectrum of the respective frequency-based data;
compare a slope of the single straight line to a pre-defined threshold; and
determine whether wind noise is present in the spectrum of the respective frequency-based data based on the slope.
18. The apparatus of claim 10 , where the signal analyzer is configured to:
fit a single straight line to a portion of a spectrum of the respective frequency-based data;
compare an intersection point of the single straight line to a pre-defined threshold; and
determine whether wind noise is present in the spectrum of the respective frequency-based data based on the intersection point.
19. A computer program product, comprising:
a non-transitory computer usable storage medium having computer readable program code embodied therein configured for suppressing noise, comprising:
computer readable code configured to cause a computer to receive separately by a sound detector device, at least a first signal and a second signal, wherein the first signal and the second signal being uncorrelated to each other both in phase and in amplitude;
computer readable code configured to cause a computer to perform separately, a time-frequency transform on the first signal and the second signal to obtain respective transformed data, wherein the first signal and the second signal remain uncorrelated to each other both in phase and in amplitude when respectively being time-frequency transformed;
computer readable code configured to cause the computer to perform signal analysis on the respective transformed data to identify wind noise in the respective transformed data that is caused by wind pressure fluctuations associated with wind striking a portion of the sound detector device, wherein the computer identifies the wind noise by detecting a difference of both the amplitude and the phase between a plurality of signal peaks that comprise the respective transformed data that exceed an amplitude threshold and a phase threshold, respectively to identify the wind noise; and
computer readable code configured to cause the computer to attenuate at least a portion of the wind noise identified in the respective transformed data.
20. The computer program product of claim 19 , where the computer readable code
configured to cause the computer to perform signal analysis further comprises:
computer readable code configured to cause the computer to fit a single straight line to a portion of a spectrum of the respective frequency-based data;
computer readable code configured to cause the computer to compare a slope of the single straight line and an intersection point of the line to a plurality of pre-defined thresholds; and
computer readable code configured to cause the computer to determine whether wind noise is present in the spectrum of the frequency-based data from the slope and the intersection point.