System and method for automatic room acoustic correction in multi-channel audio environments

• US 7,769,183 B2
• Filed: 06/20/2003
• Issued: 08/03/2010
• Est. Priority Date: 06/21/2002
• Status: Active Grant

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Kyriakakis, Chris, Bharitkar, Sunil
• Primary Examiner(s): Chin; Vivian
• Assistant Examiner(s): KURR, JASON RICHARD
• Application Number:
  US10/465,644
• Publication Number:
  US 20030235318A1
• Time in Patent Office: 2,601 Days
• Field of Search: 381/310, 381/61, 381/58, 381/59, 381/103, 381/97, 381/98, 381/303, 381/95, 381/96
• US Class Current: 381/59
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S
• CPC Class Codes: H04S 3/00 Systems employing more than two channels, e.g. quadraphonic H04S5/00, H04S7/00 take precedence
• CPC Class Codes: H04S 7/30 Control circuits for electronic adaptation of the sound field
• CPC Class Codes: H04S 7/302 Electronic adaptation of stereophonic sound system to listener position or orientation H04S7/301 takes precedence

Abstract

A system and a method for correcting, simultaneously at multiple-listener positions, distortions introduced by the acoustical characteristics includes intelligently weighing the room acoustical responses to form a room acoustical correction filter.

Claims

1. A method for correcting loudspeaker and room acoustics at multiple-listener positions in a reverberant room, the method comprising the steps of:

measuring a time domain room acoustical response at each listener position in a multiple-listener reverberant room, the measured room acoustical response including a loudspeaker response and a room response;

determining a general response by computing a weighted average of the time domain room acoustical responses; and

obtaining a room acoustic correction filter from only the general response;

wherein the room acoustic correction filter simultaneously corrects the room acoustics and loudspeaker acoustics at the multiple-listener positions.

2. The method according to claim 1, further including the step of generating a stimulus signal for measuring the room acoustical response at each of the listener positions.

3. The method according to claim 2, further including the step of transmitting the stimulus signal from at least one loudspeaker.

4. The method according to claim 3, wherein the stimulus signal is at least one of a logarithmic chirp signal, a broadband noise signal, a maximum length signal, or a white noise signal.

5. The method according to claim 1, wherein the general response is determined by a pattern recognition method.

6. The method according to claim 5, wherein the pattern recognition method is at least one of a hard c-means clustering method or a fuzzy c-means clustering method.

7. The method according to claim 1, further including the step of determining a minimum-phase signal and an all-pass signal from the general response.

8. The method according to claim 7, further including the step of inverting the minimum-phase signal.

9. The method according to claim 8, further including the step of determining a matched filter from the all-pass signal.

10. The method according to claim 9, further including the step of filtering the matched filter output with the inverse of the minimum-phase signal to obtain the room acoustic correction filter.

11. The method according to claim 8, wherein the room acoustic correction filter response is the inverse of the minimum-phase signal.

12. A method for generating substantially distortion-free audio at multiple-listener positions in a reverberant room environment, the method comprising the steps of:

measuring time domain acoustical characteristics of the environment at each expected listener position in the multiple-listener reverberant environment, the measured acoustical characteristics including a loudspeaker response and a room response;

determining a room acoustical correction filter from only the acoustical characteristics at each of the expected listener positions;

filtering an audio signal with the room acoustical correction filter; and

transmitting the filtered audio from at least one loudspeaker, wherein the audio signal received at said each expected listener position is substantially free of distortions.

13. The method according to claim 12, further including the step of generating a stimulus signal from at least one loudspeaker.

14. The method according to claim 13, wherein the stimulus signal is at least one of a logarithmic chirp signal, a broadband noise signal, a maximum length signal, or a white noise signal.

15. The method according to claim 12, further including the step of determining a general response by a pattern recognition method.

16. The method according to claim 15, wherein the pattern recognition method is at least one of a hard c-means clustering method or a fuzzy c-means clustering method.

17. The method according to claim 16, wherein the fuzzy c-means clustering method generates at least one cluster centroid.

18. The method according to claim 17, further including the step of forming the general response from the at least one cluster centroid.

19. The method according to claim 15, further including the step of determining a minimum-phase signal and an all-pass signal from the general response.

20. The method according to claim 19, further including the step of inverting the minimum-phase signal.

21. The method according to claim 20, further including the step of determining a matched filter from the all-pass signal.

22. The method according to claim 21, further including the step of convolving the matched filter output with the inverse of the minimum-phase signal to obtain the room acoustic correction filter.

23. The method according to claim 20, wherein the room acoustic correction filter response is the inverse of the minimum-phase signal.

24. A system for generating substantially distortion-free audio at multiple-listener positions in a reverberant room environment, the system comprising:

a filtering means for performing multiple-listener reverberant room acoustic correction, the filtering means formed from a weighted average of only measured time domain room acoustical responses, and wherein each of the room acoustical responses is measured at an expected listener position in a multiple-listener environment, the reverberant room acoustical response including a loudspeaker response and a room response;

wherein an audio signal, filtered by the room acoustic correction filtering means, is received substantially distortion-free at each of the expected listener positions.

25. The system according to claim 24, further including a stimulus signal generating means, said stimulus signal being used for measuring the acoustical characteristics at said each of the expected listener position.

26. The system according to claim 25, wherein at least one of the stimulus signal and the filtered audio signal is transmitted from at least one loudspeaker.

27. The system according to claim 26, wherein the stimulus signal is at least one of a logarithmic chirp signal, a broadband noise signal, a maximum length signal, or a white noise signal.

28. The system according to claim 24, wherein the weighted average is determined by a pattern recognition means.

29. The system according to claim 28, wherein the pattern recognition means is at least one of a hard c-means clustering system or a fuzzy c-means clustering method.

30. The system according to claim 29, wherein the fuzzy c-means clustering system generates at least one cluster centroid.

31. The system according to claim 30, wherein the weighted average is determined from the at least one cluster centroid.

32. The system according to claim 24, wherein at least one of a minimum-phase signal and an all-pass signal is generated from the weighted average.

33. The system according to claim 32, wherein the room acoustical correction filtering means includes an inverse of the minimum-phase signal.

34. The system according to claim 33, wherein a matched filter is obtained from the all-pass signal.

35. The system according to claim 34, wherein the room acoustic correction filtering means is obtained by filtering the matched filter output with the inverse of the minimum-phase signal.

36. The system according to claim 33, wherein filtering each of the acoustical responses with the room acoustical correction filter provides a substantially flat magnitude response at each of the expected listener positions.

37. A method for correcting loudspeaker and room acoustics at multiple-listener positions in a reverberant room, the method comprising the steps of:

measuring a plurality of reverberant room acoustical responses, each of the room acoustical responses including a room response and a loud speaker response, to a loud speaker signal;

clustering each room acoustical response into at least one cluster, wherein each cluster includes a centroid;

forming a general response from only the at least one centroid, the general response determined in the time domain; and

determining a room acoustic correction filter from the general response;

wherein the room acoustic correction filter corrects the room acoustics at the multiple-listener positions.

38. The method according to claim 37, further including the step of determining a stable inverse of the general response, said stable inverse being included in the room acoustic correction filter.

39. A method for correcting reverberant room acoustics at multiple-listener positions, the method comprising the steps of:

determining a general response by computing a weighted average of measured reverberant room acoustical responses in the time domain, each measured reverberant room acoustical response including a room response and a loud speaker response, wherein each room acoustical response corresponds to a sound propagation characteristics from a loudspeaker to a listener position; and

obtaining a room acoustic correction filter from only the general response;

wherein the room acoustic correction filter corrects the room acoustics at the multiple-listener positions.

40. The method according to claim 39, further including the step of generating a stimulus signal for measuring the room acoustical response at each of the listener position.

41. The system according to claim 39, wherein the general response is determined by at least one of a hard c-means clustering system or a fuzzy c-means clustering method.

42. A system for generating substantially distortion-free audio at multiple-listeners in a reverberant room environment, the system comprising:

a filtering means for performing multiple-listener reverberant room acoustic correction, the filtering means formed from a weighted average of only time domain measured room acoustical responses, the measured room acoustical responses including a room response and a loud speaker response, the weighted average computed in the time domain, and wherein each of the room acoustical responses is measured at an expected listener position in a multiple-listener environment;

wherein an audio signal, filtered by the room acoustic correction filtering means, is received substantially distortion-free at each of the expected listener positions.