# US 9,435,873 B2 · Sound source localization using phase spectrum

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- Number: US 9,435,873 B2
- Document ID: US9435873B2
- Status: Granted
- Kind: B2
- Application number: 13/182,449
- Filed: 2011-07-14
- Published: 2013-01-17
- Granted: 2016-09-06
- Earliest claimed: 2011-07-14
- Assignees: Microsoft Technology Licensing, LLC
- Applicants: Shankar Regunathan; Kazuhito Koishida; Harshavardhana Narayana Kikkeri
- Inventors: Shankar Regunathan; Kazuhito Koishida; Harshavardhana Narayana Kikkeri
- Web page: https://patentgrep.com/patent/US9435873B2

## CPC

- G01S 3/8083: {determining direction of source}
- G01S 3/8006: {Multi-channel systems specially adapted for direction-finding, i.e. having a single aerial system capable of giving simultaneous indications of the directions of different signals}
- G01S 3/82: with means for adjusting phase or compensating for time-lag errors
- H04R 3/005: {for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407)}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

An array of microphones placed on a mobile robot provides multiple channels of audio signals. A received set of audio signals is called an audio segment, which is divided into multiple frames. A phase analysis is performed on a frame of the signals from each pair of microphones. If both microphones are in an active state during the frame, a candidate angle is generated for each such pair of microphones. The result is a list of candidate angles for the frame. This list is processed to select a final candidate angle for the frame. The list of candidate angles is tracked over time to assist in the process of selecting the final candidate angle for an audio segment.

## Claims

### Claim 1

A computer-implemented process comprising:
receiving signals from a plurality of pairs of microphones into a memory;
processing the signals from the microphones to identify when the signals are active;
computing frequency spectrum data for the signals;
for each pair of active signals:
determining a phase spectrum of a cross power spectrum using the frequency spectrum data of the pair of active signals,
determining a phase distortion for the pair from the phase spectrum, and
deriving a candidate angle from the determined phase distortion; and
selecting an angle from among the candidate angles derived for the plurality of pairs of microphones.

### Claim 2 (depends on 1)

The computer-implemented process of claim 1, wherein receiving signals includes receiving each signal as a plurality of frames, and wherein processing, computing, determining and selecting are performed on a per frame basis.

### Claim 3 (depends on 1)

The computer-implemented process of claim 1, wherein selecting the angle from among the candidate angles comprises selecting the angle using information about prior candidate angles.

### Claim 4 (depends on 3)

The computer-implemented process of claim 3, wherein selecting further comprises:
tracking a history of candidate angles over multiple frames; and
updating the history with the candidate angles from the current frame.

### Claim 5 (depends on 4)

The computer-implemented process of claim 4, further comprising selecting the angle from the history which has a phase distortion less than or equal to the minimum phase distortion of all entries.

### Claim 6 (depends on 4)

The computer-implemented process of claim 4, further comprising selecting the angle from the history having an angle similar to a highest ranked candidate angle for the frame.

### Claim 7 (depends on 4)

The computer-implemented process of claim 4, further comprising selecting the angle from the history having a presence score greater than or equal to a maximum presence score of angles in the history.

### Claim 8

An article of manufacture comprising:
a computer storage medium;
computer program instructions stored on the computer storage medium which, when processed by a processing device, instruct the processing device to perform a process comprising:
receiving signals from a plurality of pairs of microphones into a memory;
processing the signals from the microphones to identify when the signals are active;
computing frequency spectrum data for the signals;
for each pair of active signals:
determining a phase spectrum of a cross power spectrum using the frequency spectrum data of the pair of active signals,
determining a phase distortion for the pair from the phase spectrum, and
deriving a candidate angle from the determined phase distortion; and
selecting an angle from among the candidate angles derived for the plurality of pairs of microphones.

### Claim 9 (depends on 8)

The article of manufacture of claim 8, wherein receiving signals includes receiving each signal as a plurality of frames, and wherein processing, computing, determining and selecting are performed on a per frame basis.

### Claim 10 (depends on 8)

The article of manufacture of claim 8, wherein selecting the angle from among the candidate angles comprises selecting the angle using information about prior candidate angles.

### Claim 11 (depends on 10)

The article of manufacture of claim 10, wherein selecting further comprises:
tracking a history of candidate angles over multiple frames; and
updating the history with the candidate angles from the current frame.

### Claim 12 (depends on 11)

The article of manufacture of claim 11, further comprising selecting the angle from the history which has a phase distortion less than or equal to the minimum phase distortion of all entries.

### Claim 13 (depends on 11)

The article of manufacture of claim 11, further comprising selecting the angle from the history having an angle similar to a highest ranked candidate angle for the frame.

### Claim 14 (depends on 11)

The article of manufacture of claim 11, further comprising selecting the angle from the history having a presence score greater than or equal to a maximum presence score of angles in the history.

### Claim 15

A computing machine comprising:
a memory;
an input for receiving signals from a plurality of pairs of microphones into the memory;
a processing unit configured to process the signals from the microphones to identify when the signals are active and compute frequency spectrum data for the signals;
wherein the processing unit is further configured to, for each pair of active signals, determine a phase spectrum of a cross power spectrum using the frequency spectrum data of the pair of active signals, determine a phase distortion for the pair using the phase spectrum, and derive a candidate angle from the phase distortion, and select an angle from among the candidate angles derived for the plurality of pairs of microphones.

### Claim 16 (depends on 15)

The computing machine of claim 15, wherein the input receives and stores each signal as a plurality of frames, and wherein the processing unit is configured to process the signals on a per frame basis.

### Claim 17 (depends on 15)

The computing machine of claim 15, wherein the memory further stores a history of candidate angles over multiple frames, and the processing unit is configured to update the history with the candidate angles from the current frame.

### Claim 18 (depends on 17)

The computing machine of claim 17, wherein the angle selected from the history has a phase distortion less than or equal to the minimum phase distortion of all entries.

### Claim 19 (depends on 17)

The computing machine of claim 17, wherein the angle selected from the history has an angle similar to a highest ranked candidate angle for the frame.

### Claim 20 (depends on 17)

The computing machine of claim 17, wherein the angle selected from the history has a presence score greater than or equal to a maximum presence score of angles in the history.