Directional acoustic signal processor and method therefor

• US 6,002,776 A
• Filed: 09/18/1995
• Issued: 12/14/1999
• Est. Priority Date: 09/18/1995
• Status: Expired due to Term

• Current Assignee: Interval Research Corporation
• Original Assignee: Interval Research Corporation
• Inventors: Ngo, John-Thomas Calderon, Bhadkamkar, Neal Ashok
• Primary Examiner(s): Lee, Ping
• Application Number:
  US08/531,143
• Time in Patent Office: 1,548 Days
• Field of Search: 381/66, 381/94, 381/93, 381/96, 381/94.1, 381/94.7, 379/410, 379/390, 379/395, 379/406, 455/33.1
• US Class Current: 381/66
• CPC Class Codes: G10K 11/341 Circuits therefor
• CPC Class Codes: G10K 2210/108 Communication systems, e.g. where useful sound is kept and noise is cancelled
• CPC Class Codes: G10K 2210/3028 Filtering, e.g. Kalman filters or special analogue or digital filters
• CPC Class Codes: G10K 2210/505 Echo cancellation, e.g. multipath-, ghost- or reverberation-cancellation
• CPC Class Codes: H04M 9/00 Arrangements for interconnection not involving centralised switching
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23
• CPC Class Codes: H04R 25/407 Circuits for combining signals of a plurality of transducers
• CPC Class Codes: H04R 29/006 Microphone matching
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

Two or more microphones are mounted in an environment that contains an equal or lesser number of distinct sound sources. Acoustic energy from each source, with its attendant echoes and reverberation, impinges on each microphone. Using direction-of-arrival information, a first module attempts to extract the original source signals as if the acoustic environment were anechoic. Any residual crosstalk between the channels, which may be caused by echoes and reverberation, is removed by a second module. The first and second modules may be implemented using existing technology.

Claims

1. A signal processing system for processing waves from a plurality of sources, said system comprising:

a plurality of transducer means for receiving waves from said plurality of sources, including echoes and reverberation thereof and for generating a plurality of signals in response thereto, wherein each of said plurality of transducer means receives waves from said plurality of sources including echoes and reverberations thereof, and for generating one of said plurality of signals;

first processing means for receiving said plurality of signals and for generating a plurality of first processed signals in response thereto, said first processing means comprises;

a plurality of delay means, each for receiving one of said plurality of signals and for generating a delayed signal in response thereto, and

a plurality of first combining means, each for receiving at least one of said plurality of signals and one of said delayed signals not associated with said one of said plurality of signals, and for combining said received delayed signal and said signal, by an active cancellation process, to produce one of said first processed signals; and

second processing means for receiving said plurality of first processed signals and for generating a plurality of second processed signals in response thereto, wherein each of said second processed signals represents waves from one different source, said second processing means including feedback means for supplying said plurality of second processed signals to said second processing means for combining each of said plurality of second processed signals with at least one of said plurality of first processed signals not associated with said each second processed signal to generate said plurality of second processed signals.

3. The system of claim 1, further comprising:

means for generating a direction of arrival signal for said waves; and

wherein said first processing means generates said plurality of first processed signals, in response to said direction of arrival signal.

4. The system of claim 1, wherein the number of transducer means is two, the number of first processed signals is two, and the number of second processed signals is two.

5. The system of claim 1, wherein said transducer means are spaced apart omnidirectional microphones.

6. The system of claim 1 wherein said microphones are co-located directional microphones.

7. The system of claim 1, 3, 4, 5, 6, or 2 wherein said second processing means comprises:

a plurality of second combining means, each of said second combining means having a first input, at least one other input, and an output;

each of said second combining means for receiving one of said first processed signals at said first input, an input signal at said other input, and for generating an output signal, at said output;

said output signal being one of said plurality of second processed signals and is a difference between said first processed signal received at said first input and the sum of said input signal received at said other input;

a plurality of adaptive filter means for generating a plurality of adaptive signals, each of said adaptive filter means for receiving said output signal from one of said plurality of second combining means and for generating an adaptive signal in response thereto; and

means for supplying each of said plurality of adaptive signals to one of said other input of said plurality of second combining means other than the associated one of said second combining means.

8. The system of claim 7 further comprising means for filtering each of said second processed signals to generate a plurality of third processed signals.

9. The system of claim 8 wherein said second processed signals are characterized by having a low frequency component and a high frequency component, and wherein said filtering means boosts the low frequency component relative to the high frequency component of said second processed signals.

2. A signal processing system for processing waves from a plurality of sources, said system comprising:

a plurality of transducer means for receiving waves from said plurality of sources, including echoes and reverberation thereof and for generating a plurality of signals in response thereto, wherein each of said plurality of transducer means receives waves from said plurality of sources including echoes and reverberations thereof, and for generating one of said plurality of signals;

first processing means for receiving said plurality of signals and for generating a plurality of first processed signals in response thereto, said first processing means comprises;

a plurality of multiplying means, each for receiving different ones of said plurality of signals and for generating a scaled signal in response thereto, and

a plurality of first combining means, each for receiving at least one of said plurality of signals and one scaled signal not associated with said one of said plurality of signals, and for combining said received scaled signal and said signal to produce one of said first processed signals; and

second processing means for receiving said plurality of first processed signals and for generating a plurality of second processed signals in response thereto, wherein each of said second processed signals represents waves from one different source, said second processing me including feedback means for supplying said plurality of second processed signals to said second processing means for combining each of said plurality of second processed signals with at least one of said plurality of first processed signals not associated with said each second processed signal to generate said plurality of second processed signals.

10. A signal processing system for processing waves from a plurality of sources, said system comprising:

a plurality of transducer means for receiving waves from said plurality of sources, including echoes and reverberations thereof and for generating a plurality of signals in response thereto, wherein each of said plurality of transducer means receives waves from said plurality of sources including echoes and reverberations thereof, and for generating one of said plurality of signals;

first processing means for receiving said plurality of signals and for generating a plurality of first processed signals in response thereto, wherein in the absence of echoes and reverberations of said waves from said plurality of sources, each of said first processed signals represents waves from only one different source;

said first processing means comprising;

a plurality of delay means, each for receiving one of said plurality of signals and for generating a delayed signal in response thereto, and

a plurality of first combining means, for receiving said plurality of signals and for feedforward combining said plurality of signals in an active cancellation process to produce said plurality of processed signals, wherein each of said plurality of first combining means receives at least one of said plurality of signals and one of said delayed signals not associated with said one of said plurality of signals, and for combining said received delayed signal and said one signal to produce one of said first processed signals; and

second processing means for receiving said plurality of first processed signals and for generating a plurality of second processed signals in response thereto, wherein in the presence of echoes and reverberations of said waves from said plurality of sources, each of said second processed signals represents waves from one different source;

said second processing means including feedback means for supplying said plurality of second processed signals to said second processing means for combining each of said plurality of second processed signals with at least one of said plurality of first processed signals not associated with said each second processed signal to generate said plurality of second processed signals.

12. The system of claim 10 wherein said waves are acoustic waves, and said transducer means are microphones.

13. The system of claim 12 further comprising means for filtering each of said second processed signals to generate a plurality of third processed signals.

14. The system of claim 13 wherein said second processed signals are characterized by having a low frequency component and a high frequency component, and wherein said filtering means boosts the low frequency component relative to the high frequency component of said second processed signals.

15. The system of claim 10, wherein the number of transducer means is two, the number of first processed signals is two, and the number of second processed signals is two.

16. The system of claim 10, wherein said transducer means are spaced apart omnidirectional microphones.

17. The system of claim 10 wherein said microphones are co-located directional microphones.

18. The system of claim 10, 12, 13, 14, 15, 16, 17 or 11 wherein said second processing means comprises:

a plurality of second combining means, each of said second combining means having a first input, at least one other input, and an output;

each of said second combining means for receiving one of said first processed signals at said first input, an input signal at said other input, and for generating an output signal, at said output;

said output signal being one of said plurality of second processed signals and is a difference between said first processed signal received at said first input and the sum of said input signal received at said other input;

a plurality of adaptive filter means for generating a plurality of adaptive signals, each of said adaptive filter means for receiving said output signal from one of said plurality of second combining means and for generating an adaptive signal in response thereto; and

means for supplying each of said plurality of adaptive signals to one of said other input of said plurality of second combining means other than the associated one of said second combining means.

19. The system of claim 18 wherein each of said adaptive filter means comprises a tapped delay line.

11. A signal processing system for processing waves from a plurality of sources, said system comprising:

a plurality of transducer means for receiving waves from said plurality of sources, including echoes and reverberations thereof and for generating a plurality of signals in response thereto, wherein each of said plurality of transducer means receives waves from said plurality of sources including echoes and reverberations thereof, and for generating one of said plurality of signals;

first processing means for receiving said plurality of signals and for generating a plurality of first processed signals in response thereto, wherein in the absence of echoes and reverberations of said waves from said plurality of sources, each of said first processed signals represents waves from only one different source;

said first processing means comprising;

a plurality of first combining means, for receiving said plurality of signals and for feedforward combining said plurality of signals in an active cancellation process to produce said plurality of processed signals,

a plurality of multiplying means, each for receiving different ones of said plurality of signals and for generating a scaled signal in response thereto; and

wherein each of said plurality of first combining means receives at least one scaled signal and one of said plurality of signals not associated with said one scaled signal, and for combining said received scaled signal and said signal to produce one of said first processed signals;

second processing means for receiving said plurality of first processed signals and for generating a plurality of second processed signals in response thereto, wherein in the presence of echoes and reverberations of said waves from said plurality of sources, each of said second processed signals represents waves from one different source;

said second processing means including feedback means for supplying said plurality of second processed signals to said second processing means for combining each of said plurality of second processed signals with at least one of said plurality of first processed signals not associated with said each second processed signal to generate said plurality of second processed signals.

20. A method of processing waves from a plurality of sources, comprising:

receiving said waves, including echoes and reverberations thereof, by a plurality of transducer means;

converting said waves, including echoes and reverberations thereof from said plurality of sources, by each of said plurality of transducer means into an electrical signal, thereby generating a plurality of electrical signals;

first processing said plurality of electrical signals, by an active cancellation process, to generate a plurality of first processed signals, wherein in the absence of echoes and reverberations of said waves from said plurality of sources, each of said first processed signals represents waves from one source, and a reduced amount of waves from other sources, said first processing step including;

delaying each one of said plurality of electrical signals and generating a delayed signal in response thereto, and

combining each one of said plurality of electrical signals with one of said delayed signals not associated with said one of said plurality of signals to generate one of said first processed signals; and

then

secondly processing said plurality of first processed signals to generate a plurality of second processed signals, including combining each of said plurality of second processed signals with at least one of said plurality of first processed signals not associated with said each second processed signal to generate said plurality of second processed signals, wherein in the presence of echoes and reverberations of said waves from said plurality of sources, each of said second processed signals represents waves from only one different source.

21. The method of claim 20 further comprising the step of:

filtering each of said second processed signals to generate a plurality of third processed signals.

22. The method of claim 20 further comprising the step of:

sampling and converting each one of said plurality of electrical signals and for supplying same to said plurality of delay means and to said plurality of combining means, as said electrical signal.

23. The method of claim 20 wherein said second processing step further comprises:

subtracting, by a plurality of subtracting means, a different one of said first processed signals by an adaptive signal and generating an output signal, thereby generating a plurality of output signals;

adaptively filtering said output signals to generate a plurality of adaptive signals; and

supplying each one of said plurality of adaptive signals to a different one of said subtracting means.

24. A signal processing system for processing waves from a plurality of sources, said system comprising:

at least a first and second transducer for receiving waves from said plurality of sources, including echoes and reverberation thereof and for generating at least a first and a second signal in response thereto, wherein each of said transducers receives waves from said plurality of sources including echoes and reverberations thereof, and for generating one of said first and second signals;

first processing means for receiving said first and second signals and for generating a first and a second processed signals in response thereto, said first processing means comprises;

first delay means for receiving said first signal and for generating a first delayed signal in response thereto,

second delay means for receiving said second signal and for generating a second delayed signal in response thereto,

first combining means for receiving said first signal and said second delayed signal, and for combining said received first signal and said second delay signal, by an active cancellation process, to produce said first processed signal, and

second combining means for receiving said second signal and said first delayed signal, and for combining said received second signal and said first delayed signal, by an active cancellation process, to produce said second processed signal; and

second processing means for receiving said first and second processed signals and for generating a third and a fourth processed signals in response thereto, said second processing means comprises;

third combining means for receiving the first processed signal to produce the third processed signal in response thereto;

fourth combining means for receiving the second processed signal to produce the fourth processed signal in response thereto;

first adaptive filter means for receiving said third processed signal, for generating a first adaptive signal in response thereto, and for supplying said first adaptive signal to said fourth combining means;

second adaptive filter means for receiving said fourth processed signal, for generating a second adaptive signal in response thereto, and for supplying said second adaptive signal to said third combining means;

wherein the third combining means combines the first processed signal and the second adaptive signal to produce the third processed signal so that the third processed signal is a difference between the first processed signal and the second adaptive signal; and

wherein the fourth combining means combines the second processed signal and the first adaptive signal to produce the fourth processed signal so that the fourth processed signal is a difference between the second processed signal and the first adaptive signal.