# US 7,610,197 B2 · Method and apparatus for comfort noise generation in speech communication systems

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- Number: US 7,610,197 B2
- Document ID: US7610197B2
- Status: Granted
- Kind: B2
- Application number: 11/216,624
- Filed: 2005-08-31
- Published: 2007-03-01
- Granted: 2009-10-27
- Earliest claimed: 2005-08-31
- Assignees: Motorola, Inc.
- Inventors: Edgardo M. Cruz-Zeno; James P. Ashley
- Web page: https://patentgrep.com/patent/US7610197B2

## CPC

- G10L 19/012: Comfort noise or silence coding
- G10L 19/005: Correction of errors induced by the transmission channel, if related to the coding algorithm
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

A method that may be used in variety of electronic devices for generating comfort noise includes receiving a plurality of information frames indicative of speech plus background noise, estimating one or more background noise characteristics based on the plurality of information frames, and generating a comfort noise signal based on the one or more background noise characteristics. The method may further include generating a speech signal from the plurality of information frames, and generating an output signal by switching between the comfort noise signal and the speech signal based on a voice activity detection.

## Claims

### Claim 1

An apparatus for comfort noise generation in a speech communication system, comprising a decoder configured to receive a plurality of information frames indicative of speech plus background noise; estimate one or more background noise characteristics based on the plurality of information frames wherein
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and wherein:
Ebgn(m,i) is an estimated background noise energy value of an ith frequency channel of an mth frame of the plurality of information frames,
Ech(m,i) is a estimated channel energy value of the ith frequency channel of the mth frame of the plurality of information frames,
Ebgn(m−1,i) is an estimated background noise energy value of the ith frequency channel of the (m-1)th frame of the plurality of frequency frames,
Δ1 is a first incremental energy value,
Δ2 is a second incremental energy value, and
Evoice.is an energy value indicative of voice energy; and generate a comfort noise signal based on the one or more background noise characteristics.

### Claim 2

An apparatus for comfort noise generation in a speech communication system, comprising a decoder configured to receive a plurality of information frames indicative of speech plus background noise; estimate one or more background noise characteristics based on the plurality of information frames wherein
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otherwise
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and wherein
Ebgn(m,i) is an estimated background noise energy value of an ith frequency channel of an mth frame of the plurality of information frames,
Ech(m,i) is a estimated channel energy value of the ith frequency channel of the mth frame of the plurality of information frames,
Ebgn(m−1,i) is an estimated background noise energy value of the ith frequency channel of the (m-1)th frame of the plurality of frequency frames, and
Δis an incremental energy value; and generate a comfort noise signal based on the one or more background noise characteristics.

### Claim 3 (depends on 2)

The apparatus according to claim 2 further comprising:
a radio frequency receiver to receive a radio signal that includes the information frame and a speaker to present the comfort noise.

### Claim 4

A method for comfort noise generation in a speech communication system, comprising:
receiving a plurality of information frames indicative of speech plus background noise;
estimating one or more background noise characteristics based on the plurality of information frames wherein
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otherwise
Ebgn(m,i) is an estimated background noise energy value of an ith frequency channel of an mth frame of the plurality of information frames,
Ech(m,i) is a estimated channel energy value of the ith frequency channel of the mth frame of the plurality of information frames,
Ebgn(m−1,i) is an estimated background noise energy value of the ith frequency channel of the (m−1)th frame of the plurality of frequency frames, and
Δ is an incremental energy value; and
generating a comfort noise signal based on the one or more background noise characteristics.

### Claim 5 (depends on 4)

The method according to claim 4, wherein Δ is at most 0.5 dB.

### Claim 6 (depends on 4)

The method according to claim 4, further comprising:
generating a speech signal from the plurality of information frames; and
generating an output signal by switching between the comfort noise signal and the speech signal based on a voice activity detection.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the voice activity detection is based on non-receipt of information frames containing active voice for a predetermined time.

### Claim 8 (depends on 6)

The method according to claim 6, wherein the switching between the comfort noise and the speech signal is performed using an overlap function.

### Claim 9 (depends on 1)

The method according to claim 1, wherein generating the comfort noise signal comprises performing an inverse discrete Fourier transform of spectral components derived from the background noise characteristics.

### Claim 10 (depends on 9)

The method according to claim 9, wherein the spectral components are derived to have random phases.

### Claim 11

A method for comfort noise generation in a speech communication system, comprising:
receiving in a packet decoder a plurality of information frames indicative of speech plus background noise;
estimating by a background noise estimator one or more background noise characteristics based on the plurality of information frames wherein
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ch
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+
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;
(
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>
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voice
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bgn
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m
-
1
,
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+
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2
;
otherwise
and wherein:
Ebgn(m,i) is an estimated background noise energy value of an ith frequency channel of an mth frame of the plurality of information frames,
Ech(m,i) is a estimated channel energy value of the ith frequency channel of the mth frame of the plurality of information frames,
Ebgn(m−1,i) is an estimated background noise energy value of the ith frequency channel of the (m−1)th frame of the plurality of frequency frames,
Δ1 is a first incremental energy value,
Δ2 is a second incremental energy value, and
Evoice, is an energy value indicative of voice energy; and
generating a comfort noise signal based on the one or more background noise characteristics.

### Claim 12 (depends on 11)

The method according to claim 11, wherein:
Δ1 is at most 0.5 dB;
Δ2 is at most 1.0 dB; and
Evoice, is less than 50 dB.