Speech dereverberation methods, devices and systems
Improved audio data processing method and systems are provided. Some implementations involve dividing frequency domain audio data into a plurality of subbands and determining amplitude modulation signal values for each of the plurality of subbands. A band-pass filter may be applied to the amplitude modulation signal values in each subband, to produce band-pass filtered amplitude modulation signal values for each subband. The band-pass filter may have a central frequency that exceeds an average cadence of human speech. A gain may be determined for each subband based, at least in part, on a function of the amplitude modulation signal values and the band-pass filtered amplitude modulation signal values. The determined gain may be applied to each subband.
1. A method, comprising:
receiving a signal that includes frequency domain audio data;
applying a filterbank to the frequency domain audio data to produce frequency domain audio data in a plurality of subbands;
determining amplitude modulation signal values for the frequency domain audio data in each subband;
applying a band-pass filter to the amplitude modulation signal values in each subband to produce band-pass filtered amplitude modulation signal values for each subband, the band-pass filter having a central frequency that exceeds an average cadence of human speech;
determining a gain for each subband based, at least in part, on a function of the amplitude modulation signal values and the band-pass filtered amplitude modulation signal values; and
applying a determined gain to each subband.
2. The method of claim 1 , wherein the process of determining amplitude modulation signal values involves determining log power values for the frequency domain audio data in each subband.
3. The method of claim 1 , wherein a band-pass filter for a lower-frequency subband passes a larger frequency range than a band-pass filter for a higher-frequency subband.
4. The method of claim 1 , wherein the band-pass filter for each subband has a central frequency in the range of 10-20 Hz.
5. The method of claim 4 , wherein the band-pass filter for each subband has a central frequency of approximately 15 Hz.
6. The method of claim 1 , wherein the function includes an expression in the form of R10 A .
7. The method of claim 6 , wherein R is proportional to a band-pass filtered amplitude modulation signal value divided by an amplitude modulation signal value.
8. The method of claim 6 , wherein A is proportional to an amplitude modulation signal value minus a band-pass filtered amplitude modulation signal value.
9. A non-transitory medium having software stored thereon, the software including instructions for controlling at least one apparatus to perform the method of claim 1 .
10. A device, comprising:
an interface system; and
a logic system configured to
receive, via the interface system, a signal that includes frequency domain audio data;
apply a filterbank to the frequency domain audio data to produce frequency domain audio data in a plurality of subbands;
determine amplitude modulation signal values for the frequency domain audio data in each subband;
apply a band-pass filter to the amplitude modulation signal values in each subband to produce band-pass filtered amplitude modulation signal values for each subband, the band-pass filter having a central frequency that exceeds an average cadence of human speech;
determine a gain for each subband based, at least in part, on a function of the amplitude modulation signal values and the band-pass filtered amplitude modulation signal values; and
apply a determined gain to each subband.
11. The device of claim 10 , wherein the process of determining amplitude modulation signal values involves determining log power values for the frequency domain audio data in each subband.
12. The device of claim 10 , wherein a band-pass filter for a lower-frequency subband passes a larger frequency range than a band-pass filter for a higher-frequency subband.
13. The device of any one of claim 10 , wherein the band-pass filter for each subband has a central frequency in the range of 10-20 Hz.
14. The device of claim 13 , wherein the band-pass filter for each subband has a central frequency of approximately 15 Hz.
15. The device of claim 10 , wherein the function includes an expression in the form of R10 A .
16. The device of claim 15 , wherein R is proportional to a band-pass filtered amplitude modulation signal value divided by an amplitude modulation signal value.
17. The device of claim 15 , wherein A is proportional to an amplitude modulation signal value minus a band-pass filtered amplitude modulation signal value.
18. The device of claim 15 , wherein A includes a constant that indicates a rate of suppression.
19. The device of claim 15 , wherein determining the gain involves determining whether to apply a gain value produced by the expression in the form of R10 A or a maximum suppression value.
20. The device of claim 10 , wherein the logic system is further configured to
determine a diffusivity of an object; and
determine the maximum suppression value for the object based, at least in part, on the diffusivity.