Technique for subwoofer distance measurement

• US 7,949,139 B2
• Filed: 12/03/2004
• Issued: 05/24/2011
• Est. Priority Date: 09/23/2004
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: McKee Cooper, Joel C.
• Primary Examiner(s): Chin; Vivian
• Assistant Examiner(s): Tran; Con P
• Application Number:
  US11/002,102
• Publication Number:
  US 20060062397A1
• Time in Patent Office: 2,363 Days
• Field of Search: 381/58, 381/59, 381/95, 381/96, 381/91, 381/122, 381/103, 381/56, 381/105, 702/149, 702/150, 702/85, 702/94, 702/97, 702/104, 702/176, 702/158, 735/97, 736/02, 735/84, 181/123, 181/124, 181/125, 342/77, 367/118, 367/99
• US Class Current: 381/58
• CPC Class Codes: G01S 11/14 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: H04S 7/301 Automatic calibration of stereophonic sound system, e.g. with test microphone

Abstract

The present invention automatically corrects for subwoofer or other speaker crossover settings or other parameters by providing an adjustable factor passed upon not only pulse location, but on pulse width. In FIG. 2, as the low-pass frequency of the subwoofer is decreased, either by the crossover setting or the physical design of the subwoofer, the impulse response is shifted to the right and the width of the impulse increases. By relating the adjustment factor to the width of the impulse, the accuracy of the computed distance is greatly increased. The relation may be found doing a simple polynomial curve fitting to empirical data from several subwoofers at various crossover settings and distances, storing that data, and then measuring pulse location and width of the actual subwoofer during the setup routine, and adjusting the distance (delay) calculations accordingly.

Claims

1. A method for measuring distance between an audio loudspeaker and a selected location, comprising:

placing a microphone at the selected location,

outputting an audio test signal from the audio loudspeaker,

receiving the audio test signal at the microphone,

measuring an impulse response to the audio test signal from the audio loudspeaker at the microphone to detect both a time delay of an initial pulse of the impulse response and width of the initial pulse of the impulse response at a predetermined level,

calculating an initial raw distance value from the audio loudspeaker to the selected location as a function of the time delay of the initial pulse by retrieving, from a database, data correlating predetermined audio loudspeaker type characteristics and the time delay of the initial pulse to distance between the audio loudspeaker and the microphone, and

applying the audio loudspeaker type characteristics, the time delay of the initial pulse, and width of the initial pulse to the data in the data base to output a correction factor for correcting distance calculation between the audio loudspeaker and the selected location and calculating a corrected distance value from the audio loudspeaker to the selected location by subtracting from the initial raw distance value, the pulse width of the initial pulse multiplied by the correction factor.

2. The method of claim 1, wherein outputting an audio signal comprises generating a predetermined audio signal pattern including a pseudorandom noise from the audio loudspeaker.

3. The method of claim 1, wherein outputting an audio signal comprises generating a predetermined audio signal pattern including a maximum length sequence from the audio loudspeaker.

4. A method for measuring distance between an audio loudspeaker and a microphone at a selected location, the audio loudspeaker and microphone being coupled together with a system, the method comprising:

measuring an impulse response of the system to produce an impulse response signal having an initial pulse by outputting an audio signal from the audio loudspeaker, and measuring the response to the audio signal at the microphone, and

calculating the distance from the audio loudspeaker to the microphone from a time delay of the initial pulse and the width of the initial pulse by;

retrieving, from a database, data correlating predetermined audio loudspeaker type characteristics, the time delay of the initial pulse, and the width of the initial pulse to distance between the audio loudspeaker to the microphone, and

applying the audio loudspeaker type characteristics, the time delay of the initial pulse, and width of the initial pulse to the data in the data base to output a correction factor for correcting distance calculation between the audio loudspeaker and the selected location

wherein the data correlating predetermined audio loudspeaker type characteristics, the time delay of the initial pulse, and the width of the initial pulse to distance between the audio loudspeaker, and the correction factor are determined by a measured relationship between pulse width, peak location, subwoofer characteristics, and actual measured distance,

wherein the measured relationship is predetermined empirically by testing procedures in a laboratory setting, comprising

locating various speaker types at various distances from a test microphone

generating a test signal from the various speakers types,

measuring impulse response at the microphone,

collecting pulse width, pulse location, for the various speaker types at the various distances from the microphone, and

calculating a mathematical relationship between the various distances, pulse width, and peak location to create the predetermined relation.

5. The method of claim 4, wherein the predetermined relation comprises a polynomial equation relating the time delay of the initial pulse and the width of the initial pulse to the distance from the audio loudspeaker to the microphone.

6. The method of claim 4, wherein the predetermined relation comprises a lookup table correlating the time delay of the initial pulse and the width of the initial pulse to the distance from the audio loudspeaker to the microphone.

7. The method of claim 4, wherein outputting an audio signal comprises generating a predetermined audio signal pattern including a pseudorandom noise from the audio loudspeaker.

8. The method of claim 4, wherein outputting an audio signal comprises generating a predetermined audio signal pattern including a maximum length sequence from the audio loudspeaker.

9. An apparatus for measuring distance between an audio loudspeaker and a selected location, the apparatus comprising:

an audio input for receiving an audio signal from a microphone placed at the selected location,

an audio output for providing an audio signal from the audio loudspeaker,

an impulse response measurement system for measuring an impulse response to the audio signal at the microphone, to detect a time delay of an initial pulse of the impulse response and a pulse width of the initial pulse of the impulse response, and

a processor for calculating an initial raw distance value from the audio loudspeaker to the selected location as a function of the time delay of the initial pulse, the processor including a database for storing data correlating predetermined audio loudspeaker type characteristics and the time delay of the initial pulse to distance between the audio loudspeaker and the microphone,

wherein the processor applies the time delay of the initial pulse and width of the initial pulse to the data in the data base to output a correction factor for correcting distance calculation between the audio loudspeaker and the selected location and calculates a corrected distance value from the audio loudspeaker to the selected location by subtracting from the initial raw distance value, the width of the initial pulse multiplied by the correction factor.

10. The apparatus of claim 9, wherein the audio output generates a predetermined audio signal pattern including a pseudorandom noise from the audio loudspeaker.

11. The apparatus of claim 9, wherein the audio output generates a predetermined audio signal pattern including a maximum length sequence from the audio loudspeaker.

12. A system for measuring distance between an audio loudspeaker and a microphone at a selected location, the audio loudspeaker and microphone being coupled together with the system, the system comprising:

an impulse response measurement sub-system for measuring an impulse response of a system to produce a response signal having an initial pulse by outputting an audio signal from the audio loudspeaker, and measuring the response to the audio signal at the microphone, and

a processor for calculating the distance from the audio loudspeaker to the microphone from a time delay of the initial pulse and the width of the initial pulse, the processor including;

a database for storing data correlating predetermined audio loudspeaker type characteristics, the time delay of the initial pulse, and the width of the initial pulse to distance between the audio loudspeaker to the microphone,

wherein the processor applies the time delay of the initial pulse and the width of the initial pulse to the data in the database, to output a correction factor for correcting distance calculation between the audio loudspeaker and the selected location using a predetermined relation depending upon the measured relationship between pulse width, peak location, subwoofer characteristics, and actual measured distance,

wherein the predetermined relation is predetermined empirically by testing procedures in a laboratory setting, comprising;

locating various speaker types at various distances from a test microphone,

generating a test signal from the various speakers types,

measuring impulse response at the microphone,

collecting pulse width and pulse location, for the various speaker types at the various distances from the microphone, and

calculating a mathematical relationship between the various distances, pulse width, and peak location to create the predetermined relation.

13. The system of claim 12, wherein the predetermined relation comprises an equation relating the time delay of the initial pulse and the width of the initial pulse to the distance from the audio loudspeaker to the microphone.

14. The system of claim 12, wherein the predetermined relation comprises a lookup table correlating the time delay of the initial pulse and the width of the initial pulse to the distance from the audio loudspeaker to the microphone.

15. The system of claim 12, wherein the audio output generates a predetermined audio signal pattern including a pseudorandom noise from the audio loudspeaker.

16. The system claim 12, wherein the audio output generates a predetermined audio signal pattern including a maximum length sequence from the audio loudspeaker.

17. A home theater system provided with an auto-setup mode for measuring distance between an audio loudspeaker and a selected listening location and delaying audio signals to the audio loudspeaker proportionally to the distance between the audio loudspeaker and the selected location, the home theater system, comprising:

an audio output for generating an audio test signal to the at least one audio loudspeaker,

at least one audio loudspeaker for receiving the audio test signal and generating an acoustical audio signal,

a microphone, for receiving the acoustical audio signal when the microphone is placed at the selected listening location and outputting a received audio test signal,

an impulse response measurement system for measuring an impulse response to the received audio test signal at the microphone, to detect a time delay of an initial pulse of the impulse response and a width of the initial pulse of the impulse response, and

a processor for calculating an initial raw distance value from the audio loudspeaker to the selected location as a function of the time delay of the initial pulse of the impulse response and adjusting a time delay for audio signals generated by the at least one audio loudspeaker, the processor including a database for storing data correlating predetermined audio loudspeaker type characteristics and the time delay of the initial pulse of the impulse response to distance between the audio loudspeaker and the microphone,

wherein the processor applies the time delay of the initial pulse of the impulse response and width of the initial pulse of the impulse response to the data in the data base to output a correction factor for correcting distance calculation between the audio loudspeaker and the selected location and calculates a corrected distance value from the audio loudspeaker to the selected location by subtracting from the initial raw distance value, the width of the initial pulse of the impulse response multiplied by the correction factor.

18. The home theater system of claim 17, wherein the audio output generates a predetermined audio signal pattern including a pseudorandom noise from the audio loudspeaker.

19. The home theater system of claim 17, wherein the audio output generates a predetermined audio signal pattern including a maximum length sequence from the audio loudspeaker.