METHOD FOR ENCODING MULTIPLE MICROPHONE SIGNALS INTO A SOURCE-SEPARABLE AUDIO SIGNAL FOR NETWORK TRANSMISSION AND AN APPARATUS FOR DIRECTED SOURCE SEPARATION

• US 20120269332A1
• Filed: 04/20/2012
• Published: 10/25/2012
• Est. Priority Date: 04/20/2011
• Status: Active Grant

• Current Assignee: Plantronics, Inc.
• Original Assignee: Plantronics, Inc.
• Inventors: Mukund, Shridhar K.
• Granted Patent: US 8,670,554 B2
• Time in Patent Office: Days
• US Class Current: 379/201.06
• CPC Class Codes: G10L 2021/02161 Number of inputs available containing the signal or the noise to be suppressed
• CPC Class Codes: G10L 25/84 for discriminating voice from noise
• CPC Class Codes: H04R 2201/40 Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
• CPC Class Codes: H04S 2400/03 Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1 H04S2400/01 takes precedence
• CPC Class Codes: H04S 3/006 in which a plurality of audio signals are transformed in a combination of audio signals and modulated signals, e.g. CD-4 systems

Abstract

A method is provided for encoding multiple microphone signals into a composite source-separable audio (SSA) signal, conducive for transmission over a voice network. The embodiments enable the processing of source separation of the target voice signal from its ambient sound to be performed at any point in the voice communication network, including the internet cloud. A multiplicity of processing is possible over the SSA signal, based on the intended voice application. The level of processing is adapted with the availability of the processing power at the chosen processing node in the network in one embodiment. An apparatus for separating out the target source voice from its ambient sound is also provided. The apparatus includes a directed source separation (DSS) unit, which processes the two virtual microphone signals in the SSA representation, to generate a new SSA signal including the enhanced target voice and the enhanced ambient noise.

Claims

1. An apparatus for sound capture, comprising:

a plurality of microphones spatially disposed in a first group and a second group, wherein outputs of the plurality of microphones within the first group are summed together as a first output and the outputs of the plurality of microphones within the second group are summed together as a second output, thereby defining a first virtual microphone and a second virtual microphone, respectively.

2. The apparatus of claim 1, wherein the first virtual microphone and the second virtual microphone each represent an independent mixture of a target source voice and an ambient noise.

3. The apparatus of claim 2, further comprising:

an adaptive directed source separation (DSS) unit having a first input and a second input, the first input and the second input coupled to the first output of the first virtual microphone and the second output of the second virtual microphone, respectively, the DSS unit generating a first DSS output and a second DSS output, the first output comprising enhanced target source voice and the second output comprising enhanced ambient noise.

4. The apparatus of claim 3 further comprising:

a voice likelihood detector, wherein the first output of the first virtual microphone and the second output of the second virtual microphone are processed through the voice likelihood detector to generate a first control output and a second control output, the first control output representing a probability of presence of the target source voice and the second control output representing a probability of presence of the ambient noise, wherein the first control output and the second control output are supplied as a first control input and a second control input of the DSS unit.

5. The apparatus of claim 2, wherein the ambient noise is acoustic echo generated by loudspeakers located proximate to the plurality of microphones.

6. The apparatus of claim 5, further comprising:

a plurality of loudspeakers operated to maximize acoustic echo disparity between the first virtual microphone and the second virtual microphone.

7. The apparatus of claim 1, wherein the summing of the outputs of the plurality of microphones in the first group and the summing of the outputs of the plurality of microphones in the second group is realized by a passive electrical connection.

8. The apparatus of claim 1, wherein the plurality of microphones are of a digital micro electrical mechanical systems (MEMS) type, and wherein the digital output streams of the digital MEMS microphones are interleaved to realize one composite pulse digitally modulated (PDM) output.

9. The apparatus of claim 1, comprising:

a digital MEMS type microphone operable to accept an analog summing input; and

a plurality of analog MEMs microphones passively ganged together, wherein a combined output of the plurality of analog MEMS microphones is supplied to the analog summing input of the digital MEMS microphone.

10. A method for network transmission of voice, comprising:

combining two audio signals into a composite source separable audio (SSA) signal, each audio signal of the two audio signals representing an independent mixture of a target source voice and an ambient noise.

11. A method of claim 10, further comprising:

separating the two audio signals within the composite SSA signal into two mono audio signals by performing directed source separation (DSS).

12. A method of claim 10, wherein the two audio signals are digital signals and the combining process comprises interleaving the two audio signals to generate the composite SSA signal.

13. A method of claim 10, wherein the two audio signals are analog signals and the combining process comprises delaying the second audio signal and summing the delayed second audio signal with the first audio signal to generate the composite SSA signal.

14. A method of claim 10, wherein the composite SSA signal is intelligible for human listening without requiring any further processing.

15. A method of claim 11, comprising:

performing a first ambient sound separation process for human listening intelligibility; and

performing a second ambient sound separation process for a machine voice application.

16. A method of claim 11, wherein a quality of ambient sound separation is traded off gracefully, depending on the availability of processing power.

17. A method of claim 11, wherein the separating is performed in an intermediate server in a network cloud.

18. A method of claim 11, wherein the target source voice signal is suppressed and the ambient sound signal is enhanced.

19. A method of claim 11, for teleconferencing, further comprising:

generating a first SSA composite audio;

generating a second SSA composite audio;

performing directed source separation (DSS) on each of the first and second SSA signals; and

mixing resulting SSA signals.

20. A method of claim 11, further comprising:

co-transmitting a voice-band, non-voice signal, the co-transmitting comprising;

summing the non-voice signal into the first virtual microphone signal of the SSA signal;

summing the inverted non-voice signal into the second virtual microphone signal of the said SSA signal.

21. A method of network transmission of voice, comprising:

establishing a first voice call between a first transmit host and a first receive host;

establishing a second voice call between a second transmit host and second receive host, wherein the second transmit host is located in physical proximity of the first transmit host; and

using the noise from the second call to perform ambient noise suppression for the first call.

22. A method of network transmission of voice, comprising:

using ambient noise captured by a first listening device to determine a physical location of the first listening device relative to a second listening device.