In-room acoustic magnitude response smoothing via summation of correction signals

• US 8,194,874 B2
• Filed: 05/21/2008
• Issued: 06/05/2012
• Est. Priority Date: 05/22/2007
• Status: Active Grant

• Current Assignee: Polk Audio Incorporated (DEI Holdings Incorporated)
• Original Assignee: Polk Audio Incorporated (DEI Holdings Incorporated)
• Inventors: Starobin, Bradley M., Lyon, Richard H., Blair, Christopher N.
• Primary Examiner(s): Smith, Zandra
• Assistant Examiner(s): PATTON, PAUL E
• Application Number:
  US12/153,623
• Publication Number:
  US 20080298604A1
• Time in Patent Office: 1,476 Days
• Field of Search: 381/73.1, 381/71.8, 381/71.11, 381/94.9
• US Class Current: 381/73.1
• CPC Class Codes: H03G 5/025 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H03G 5/165 Equalizers; Volume or gain control in limited frequency bands
• CPC Class Codes: H04R 29/001 for loudspeakers H04R29/007 takes precedence
• CPC Class Codes: H04S 7/301 Automatic calibration of stereophonic sound system, e.g. with test microphone

Abstract

A system and method are provided for smoothing the in-room acoustic magnitude response of an audio reproduction system. An in-room acoustic magnitude response analysis is performed to determine a room resonance induced peak associated with an audio signal. A replica of the audio signal is filtered at the room resonance induced peak. The filtered replica signal is added with the audio signal. Through this, smoothing of the room resonance induced peak may be achieved, such that a subjective impression of transient response and dynamics of the audio signal are preserved.

Claims

1. A method for smoothing acoustic magnitude response of an audio reproduction system in a room that preserves subjective impression of transient response and dynamics, comprising:

a) selecting an in-room magnitude response passband lower frequency and an in-room magnitude response passband upper frequency;

b) placing subwoofer and a user-positionable microphone in a room;

c) energizing said subwoofer with an audio signal within said magnitude response passband and generating an acoustic output signal within said room;

d) performing an in-room acoustic magnitude response analysis and determining whether an addressable room resonance induced peak associated with said acoustic output signal is detectable with said microphone, wherein a room resonance induced peak is regarded as addressable if said peak'"'"'s magnitude exceeds a mean level through a passband or a prescribed sub-passband;

e) and if an addressable room resonance induced peak is detected, then filtering a replica of the audio signal at the room resonance induced peak; and

f) adding the filtered replica signal with the audio signal, whereby smoothing the room resonance induced peak is achieved, such that a subjective impression of transient response and dynamics of the audio signal are preserved.

2. The method of claim 1, wherein the determining is performed at a listening area of the room.

3. The method of claim 1, wherein the determining comprises determining a region within a low frequency range of the audio signal that exceeds a predetermined mean level by about 3 decibels to about 12 decibels.

4. The method of claim 1, wherein the replica signal is delayed a time period equal to about an odd integer of one-half of a period of a frequency of the room resonance induced peak.

5. The method of claim 1, wherein the acoustic magnitude response analysis comprises using for said audio signal a swept sine wave, a tone burst, or a maximum length sequence technique signal.

6. The method of claim 1, wherein the acoustic magnitude response analysis determines between 3 and 5 peaks per octave.

7. The method of claim 1, wherein the filtering comprises bandpass filtering.

8. The method of claim 1, wherein the replica signal is delayed a time period t_i=A/(2f_ci) wherein f_ci is a center frequency of the peak i.

9. The method of claim 8, wherein A is an odd integer less than or equal to 5.

10. The method of claim 1, wherein:

an interval between the peak and another peak is about ⅓

octave.

11. A system for smoothing acoustic magnitude response of an audio reproduction system in a room that preserves subjective impression of transient response and dynamics, comprising:

an acoustic magnitude response analysis device, wherein a room resonance induced peak is regarded as addressable if their magnitude exceeds a mean level through a passband of the loudspeaker or a prescribed sub-passband configured to determine a room resonance induced peak;

a filter configured to filter a replica of an audio signal at the room resonance induced peak; and

an adder configured to add the filtered replica signal with the audio signal, whereby a subjective impression of transient response and dynamics of the audio signal are preserved.

12. The system of claim 11, wherein the room resonance induced peak is detected at a listening area.

13. The system of claim 11, wherein the acoustic magnitude response analysis device is configured to determine the room resonance induced peak in a region within a low frequency range of the audio signal that exceeds a predetermined mean level by about 3 decibels to about 12 decibels.

14. The system of claim 11, wherein the replica signal is delayed a time period equal to about an odd integer of one-half of a period of a frequency of the room resonance induced peak.

15. The system of claim 11, wherein the acoustic magnitude response analysis device is configured to use a swept sine wave, a tone burst, or a maximum length sequence technique.

16. The system of claim 11, wherein the acoustic magnitude response analysis device is configured to determine between 3 and 5 peaks per octave.

17. The system of claim 11, wherein the filter comprises a bandpass filter.

18. The system of claim 11, wherein the replica signal is delayed a time period t_i=A/(2f_ci) wherein f_ci is a center frequency of the peak i.

19. The system of claim 18, wherein A is an odd integer less than or equal to 5.

20. The system of claim 11, wherein:

the acoustic magnitude response analysis device is configured to determine another peak; and

an interval between the peak and the another peak is about ⅓

octave.