# US 9,520,140 B2 · Speech dereverberation methods, devices and systems

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- Number: US 9,520,140 B2
- Document ID: US9520140B2
- Status: Granted
- Kind: B2
- Application number: 14/782,746
- Filed: 2014-03-31
- Published: 2016-02-04
- Granted: 2016-12-13
- Earliest claimed: 2013-04-10
- Assignees: Dolby Laboratories Licensing Corporation
- Applicants: Dolby Laboratories Licensing Corporation
- Inventors: Erwin Goesnar; Glenn N. Dickins; David Gunawan
- Web page: https://patentgrep.com/patent/US9520140B2

## CPC

- G10L 21/0232: Processing in the frequency domain
- G10L 21/0208: Noise filtering
- G10L 25/18: the extracted parameters being spectral information of each sub-band
- G10L 25/21: the extracted parameters being power information
- G10L 2021/02082: {the noise being echo, reverberation of the speech}
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

The method of claim 1, wherein the band-pass filter for each subband has a central frequency in the range of 10-20 Hz.

### Claim 5 (depends on 4)

The method of claim 4, wherein the band-pass filter for each subband has a central frequency of approximately 15 Hz.

### Claim 6 (depends on 1)

The method of claim 1, wherein the function includes an expression in the form of R10A.

### Claim 7 (depends on 6)

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.

### Claim 8 (depends on 6)

The method of claim 6, wherein A is proportional to an amplitude modulation signal value minus a band-pass filtered amplitude modulation signal value.

### Claim 9 (depends on 1)

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.

### Claim 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.

### Claim 11 (depends on 10)

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.

### Claim 12 (depends on 10)

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.

### Claim 13 (depends on 10)

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.

### Claim 14 (depends on 13)

The device of claim 13, wherein the band-pass filter for each subband has a central frequency of approximately 15 Hz.

### Claim 15 (depends on 10)

The device of claim 10, wherein the function includes an expression in the form of R10A.

### Claim 16 (depends on 15)

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.

### Claim 17 (depends on 15)

The device of claim 15, wherein A is proportional to an amplitude modulation signal value minus a band-pass filtered amplitude modulation signal value.

### Claim 18 (depends on 15)

The device of claim 15, wherein A includes a constant that indicates a rate of suppression.

### Claim 19 (depends on 15)

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 R10A or a maximum suppression value.

### Claim 20 (depends on 10)

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.