# US 8,751,220 B2 · Multiple microphone based low complexity pitch detector

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- Number: US 8,751,220 B2
- Document ID: US8751220B2
- Status: Granted
- Kind: B2
- Application number: 13/290,907
- Filed: 2011-11-07
- Published: 2013-05-09
- Granted: 2014-06-10
- Earliest claimed: 2011-11-07
- Assignees: Broadcom Corporation
- Applicants: Xianxian Zhang; Alfonsus Lunardhi
- Inventors: Xianxian Zhang; Alfonsus Lunardhi
- Web page: https://patentgrep.com/patent/US8751220B2

## CPC

- G10L 21/00: Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility (G10L19/00 takes precedence)
- G10L 25/90: Pitch determination of speech signals
- G10L 2021/02165: {Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal}
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

Various embodiments of multiple microphone based pitch detection are provided. In one embodiment, a method includes obtaining a primary signal and a secondary signal associated with multiple microphones. A pitch value is determined based at least in part upon a level difference between the primary and secondary signals. In another embodiment, a system includes a plurality of microphones configured to provide a primary signal and a secondary signal. A level difference detector is configured to determine a level difference between the primary and secondary signals and a pitch identifier is configured to clip the primary and secondary signals based at least in part upon the level difference. In another embodiment, a method determines the presence of voice activity based upon a pitch prediction gain variation that is determined based at least in part upon a pitch lag.

## Claims

### Claim 1

A method, comprising:
obtaining, by a computing device, a primary signal corresponding to a primary microphone and a secondary signal corresponding to a secondary microphone;
determining, by the computing device, a level difference between the primary and secondary signals; and
determining, by the computing device, a pitch value based at least in part upon the determined level difference of the primary and secondary signals.

### Claim 2 (depends on 1)

The method of claim 1, wherein determining the pitch value includes determining, by the computing device, a clipping level based upon the level difference.

### Claim 3 (depends on 2)

The method of claim 2, wherein determining the pitch value further includes:
clipping, by the computing device, a portion of the primary signal using the determined clipping level; and
determining, by the computing device, a pitch value associated with the portion of the primary signal based upon autocorrelation of the clipped portion of the primary signal.

### Claim 4 (depends on 3)

The method of claim 3, wherein determining the pitch value further includes determining, by the computing device, a clipping level for the secondary signal based upon the level difference.

### Claim 5 (depends on 4)

The method of claim 4, wherein determining the pitch value further includes:
clipping, by the computing device, a portion of the secondary signal using the determined clipping level for the secondary signal; and
determining, by the computing device, a pitch value associated with the portion of the secondary signal based upon autocorrelation of the clipped portion of the secondary signal.

### Claim 6 (depends on 5)

The method of claim 5, wherein determining the pitch value further includes determining, by the computing device, a final pitch value based upon the pitch value associated with the primary signal and the pitch value associated with the secondary signal.

### Claim 7 (depends on 3)

The method of claim 3, wherein the primary and secondary signals are sectioned to provide the portion of the primary signal and a corresponding portion of the secondary signal.

### Claim 8 (depends on 2)

The method of claim 2, wherein a ratio of the averaged Teager Energy Operator (TEO) energy (RTEO) of the primary and secondary signals represents the level difference between the primary and secondary signals.

### Claim 9 (depends on 8)

The method of claim 8, wherein the clipping level is based at least in part upon an adaptive factor that varies between a minimum value and a maximum value based upon the RTEO.

### Claim 10 (depends on 8)

The method of claim 8, wherein the adaptive factor varies exponentially within a defined range of the RTEO.

### Claim 11

A system, comprising:
a plurality of microphones configured to provide a primary signal and a secondary signal;
a level difference detector configured to determine a level difference between the primary and secondary signals; and
a pitch identifier configured to clip the primary and secondary signals based at least in part upon the level difference.

### Claim 12 (depends on 11)

The system of claim 11, wherein the pitch identifier is further configured to determine a pitch value based at least in part upon autocorrelation of the clipped primary signal and autocorrelation of the clipped secondary signal.

### Claim 13 (depends on 11)

The system of claim 11, wherein the pitch identifier is further configured to determine a clipping level based at least in part upon the level difference.

### Claim 14 (depends on 13)

The system of claim 13, wherein the level difference is a ratio of the averaged Teager Energy Operator (TEO) energy (RTEO) of the primary and secondary signals.

### Claim 15 (depends on 13)

The system of claim 13, wherein the primary and secondary signals are sectioned into a plurality of corresponding signal sections before clipping, each signal section including a pitch searching frame and a portion that overlaps with an adjacent signal section.

### Claim 16 (depends on 11)

The system of claim 11, wherein a primary microphone provides the primary signal and a noise reference microphone provides the secondary signal.

### Claim 17 (depends on 11)

The system of claim 11, wherein a speech output of a beamformer provides the primary signal based upon signals from the plurality of microphones and a noise output of a beamformer provides the secondary signal based upon the signals from the plurality of microphones.

### Claim 18

A method, comprising:
obtaining, by a computing device, a section of a primary signal and a corresponding section of a secondary signal, the primary and secondary signals associated with a plurality of microphones;
determining, by the computing device, a pitch value based at least in part upon a level difference between the primary signal and secondary signal;
determining, by the computing device, a pitch lag based upon the pitch value;
determining, by the computing device, a pitch prediction gain variation for the primary signal section based at least in part upon the pitch lag; and
determining, by the computing device, the presence of voice activity based upon the pitch prediction gain variation.

### Claim 19 (depends on 18)

The method of claim 18, wherein the pitch prediction gain variation is determined with a pitch searching frame of the primary signal section.

### Claim 20 (depends on 18)

The method of claim 18, wherein the pitch prediction gain variation is compared to a predefined threshold to determine the presence of voice activity.