System and process for time delay estimation in the presence of correlated noise and reverberation

• US 20050249038A1
• Filed: 07/14/2005
• Published: 11/10/2005
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Rui, Yong, Florencio, Dinei A.
• Granted Patent: US 7,113,605 B2
• Time in Patent Office: Days
• US Class Current: 367/124
• CPC Class Codes: H04R 2430/23 Direction finding using a sum-delay beam-former
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A system and process for estimating the time delay of arrival (TDOA) between a pair of audio sensors of a microphone array is presented. Generally, a generalized cross-correlation (GCC) technique is employed. However, this technique is improved to include provisions for both reducing the influence (including interference) from correlated ambient noise and reverberation noise in the sensor signals prior to computing the TDOA estimate. Two unique correlated ambient noise reduction procedures are also proposed. One involves the application of Wiener filtering, and the other a combination of Wiener filtering with a G_nn subtraction technique. In addition, two unique reverberation noise reduction procedures are proposed. Both involve applying a weighting factor to the signals prior to computing the TDOA which combines the effects of a traditional maximum likelihood (TML) weighting function and a phase transformation (PHAT) weighting function.

Claims

1. A computer-implemented process for estimating the time delay of arrival (TDOA) between a pair of audio sensors of a microphone array, comprising using a computer to perform the following process actions:

inputting signals generated by the audio sensors; and

estimating the TDOA using a generalized cross-correlation (GCC) technique which,

employs a provision for reducing the influence from correlated ambient noise, and

employs a weighting factor for reducing the influence from reverberation noise by establishing a weighting function which is a combination of a traditional maximum likelihood (TML) weighting function and a phase transformation (PHAT) weighting function.

2. The process of claim 1, wherein the process action of employing a provision in the GCC technique for reducing the influence from correlated ambient noise, comprises an action of applying Wiener filtering to the audio sensor signals.

3-22. -22. (canceled)

23. A computer-readable medium having computer-executable instructions for estimating the time delay of arrival (TDOA) between a pair of audio sensors of a microphone array, said computer-executable instructions comprising:

inputting signals generated by each audio sensor of the microphone array;

simultaneously sampling the inputted signals to produce a sequence of consecutive blocks of the signal data from each signal, wherein each block of signal data is captured over a prescribed period of time and is at least substantially contemporaneous with blocks of the other signal sampled at the same time;

for each contemporaneous pair of blocks of signal data, estimating the TDOA using a generalized cross-correlation (GCC) technique which,

employs a provision for reducing the influence from correlated ambient noise, and

employs a weighting factor for reducing the influence from reverberation noise.