System and method for selective signal cancellation for multiple-listener audio applications

• US 20040109570A1
• Filed: 06/20/2003
• Published: 06/10/2004
• Est. Priority Date: 06/21/2002
• Status: Abandoned Application

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Kyriakakis, Chris, Bharitkar, Sunil
• Application Number:
  US10/465,237
• Publication Number:
  US 20040109570A1
• Time in Patent Office: Days
• US Class Current: 381/17
• CPC Class Codes: H04R 27/00 Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F
• CPC Class Codes: H04R 29/007 for public address systems public address systems per se H04R27/00
• 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 method for producing an audio output directed to a listening environment having at least two listening positions. Based upon the location of a loudspeaker for the purpose of producing an audio output and the physical location of the listening positions, the audio output would be preprocessed by one or more filters whose coefficients would maximize the signal heard by a listener in one of the listening positions and constrained by a listener in another position, thereby eliminating or minimizing the audio output heard by a listener in one of the other positions.

Claims

1. A method for selectively presenting an audio signal to an environment having at least two listening positions, comprising the steps of:

measuring an acoustical response at a first listening position;

creating a filter by determining the gradient of an objective function, said objective function including a first term;

producing a raw audio signal;

processing said raw audio signal through said filter to produce a filtered audio signal, wherein said first term minimizing the second pressure level of said filtered audio signal at said first listening position;

transmitting said filtered audio signal from at least one loudspeaker provided within the environment, said filtered audio signal substantially cancelled at said first listening position and substantially retained at a second listening position.

2. The method of claim 1, further comprising the step of measuring an acoustical response at said second listening position.

3. The method of claim 2, further comprising the step of including a first term in said objective function for maximizing the sound pressure level of said filtered audio signal at said second listening position.

4. The method of claim 1, further comprising the step of including a second term in said objective function for constraining the sound pressure level of said filtered audio signal at said first listening position by a predetermined amount.

5. The method of claim 2, further comprising the step of including a second term in said objective function for constraining the sound pressure level of said filtered audio signal at said second listening position by a predetermined amount.

6. The method of claim 1, further including the step of transmitting a test signal from said at least one loudspeaker to measure an acoustical response in the environment.

7. The method of claim 6, further including the step of transmitting a plurality of test signals from said at least one loudspeaker to measure an acoustical response from each of the listening positions in the environment.

8. The method of claim 7, further including the step of providing a transceiver at each of the listening positions to produce a signal from each of the listening positions to measure an acoustical response from each of the listening positions in the environment.

9. The method of claim 3, further including the steps of:

transmitting a test signal from said at least one loudspeaker to measure an acoustical response in the environment, and

producing a first term of said objective function which is a function of said acoustical response.

10. The method of claim 4, further including the steps of:

transmitting a test signal from said at least one loudspeaker to measure an acoustical response in the environment, and

producing a second term of said objective function which is a function of said acoustical region.

11. The method of claim 1, wherein at least two listening positions includes a first set of listening position at which said filtered audio signal is substantially cancelled and a second set of listening positions at which said filtered audio signal is substantially retained, comprising the step of:

transmitting a test signal from said at least one loudspeaker to measure a first set of acoustical responses at said first set of listening positions.

12. The method of claim 11, wherein at least two listening positions includes a second set of listening positions at which said filtered audio signal is substantially cancelled and a second set of listening positions at which said filtered audio signal is substantially retained, comprising the step of:

transmitting a test signal from at least one loudspeaker to measure a second set of acoustical responses at said second set of listening positions.

13. The method of claim 11, further including the step of:

producing a first term of said objective function which is a function of said acoustical response.

14. The method of claim 12, further including the step of:

producing a second term of said objective function which is a function of said acoustical region.

15. The method claim 11, further including the step of averaging said first set of acoustical responses.

16. The method of claim 12, further including the step of averaging said second set of acoustical responses.

17. A system for selectively presenting an audio signal to an environment having at least two listening positions, comprising:

test signal production device for producing a test signal to be projected into the environment;

transceiver device provided within the environment for receiving said test signal and providing an acoustical response returned to said test signal production device;

a means for creating a filter by determining the gradient of an objective function based upon said response returned to said test signal production device, wherein said objective function includes a first term for minimizing the second pressure at a first listening position;

transmitting a raw audio signal through said filter to produce a filtered audio signal; and

projecting said filtered audio signal into the environment.

18. The system in accordance with claim 17 including a selection device for choosing whether a particular listening position wishes to receive a maximized filtered audio signal or a minimized signal filtered audio signal.

19. The system in accordance with claim 18 in which the environment includes a second listening position to receive said maximized filtered audio signal, wherein said means for creating a filter produces a first term of said objective function for minimizing the sound to pressure level of said filtered audio signal and a second term of said objective function for maximizing the sound pressure level of said filtered audio output.

20. The system in accordance with claim 18 in which the environment includes a first set of listening positions to receive said maximized filtered audio signal and a second set of listening positions to receive said minimized filtered audio signal, wherein said means for creating a filter produces a first term of said objective function for minimizing the sound pressure level of said filtered audio signal and a second term of said objective function for maximizing the sound pressure level of said filtered audio output.

21. The system in accordance with claim 20, wherein said means for creating said filter averages the acoustical responses received from said first set of listening positions to produce said first term and said filter averages the acoustical responses received from said second set of listening positions to produce said second term.