Method and apparatus for dynamic sound optimization

• US 5,615,270 A
• Filed: 06/06/1995
• Issued: 03/25/1997
• Est. Priority Date: 04/08/1993
• Status: Expired due to Term

• Current Assignee: Bose Corporation
• Original Assignee: International Jensen Incorporated
• Inventors: Kantor, Kenneth L., Wise, Duane K., Miller, Thomas E., Barish, Jeffrey
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US08/466,411
• Time in Patent Office: 658 Days
• Field of Search: 381/57, 381/94, 381/98, 381/71, 381/103, 381/107, 381/108
• US Class Current: 381/57
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level

Abstract

This invention comprises a system to compensate for the noise level inside a vehicle by measuring the music level and the noise level in the vehicle through the use of analog to digital conversion and adaptive digital filtering, including a sensing microphone in the vehicle cabin to measure both music and noise; preamplification and analog to digital (A/D) conversion of the microphone signal; A/D conversion of a stereo music signal; a pair of filters that use an adaptive algorithm such as the known Least Mean Squares ("LMS") method to extract the noise from the total cabin sound; an estimation of the masking effect of the noise on the music; an adaptive correction of the music loudness and, optionally, equalization to overcome the masking effect; digital to analog (D/A) conversion of the corrected music signal; and transmission of the corrected music signal to the audio system.

Claims

1. An audio enhancement system for compensating for ambient noise in a listening environment, comprising:

A. an audio signal source for producing an electrical sound signal;

B. a loudspeaker for generating a sound output from said electrical sound signal;

C. a microphone adapted for placement in a listening environment to provide a total sound signal representative of the total sound level in said environment, wherein said total sound level comprises both the sound output from said loudspeaker and the ambient noise within said environment;

D. a signal processor for subtracting said sound output from said total sound signal, thereby extracting an ambient noise signal representative of said ambient noise;

E. a gain calculator for comparing said electrical sound signal from said audio signal source with said ambient noise signal and determining their relative levels; and

F. at least a first volume control responsive to the relative levels of the electrical sound signal and the ambient noise signal for adjusting said sound output of said loudspeaker to compensate for said ambient noise.

2. An audio enhancement system as set forth in claim 1, wherein said first volume control comprises:

A. a generator for generating a control signal based on the relative levels of the electrical sound signal and the ambient noise signal determined by said gain calculator; and

a gain adjustment control responsive to said control signal for adjusting the sound output of said loudspeaker to compensate for said ambient noise level.

3. An audio enhancement system as set forth in claim 2, further comprising a second volume control for controlling the volume of said sound output, wherein said second volume control receives said electrical sound signal from said first volume control.

4. An audio enhancement system as set forth in claim 2, further comprising a second volume control for controlling the volume of said sound output, wherein said first volume control receives said electrical sound signal before it is transmitted through said second volume control.

5. An audio enhancement system as set forth in claim 1, wherein said electrical sound signal has low frequency and higher frequency components, further comprising a low frequency adjustment subsystem for adjusting the low frequency element of said sound output separately from the adjustment of said sound output by said second volume control.

6. An audio enhancement system as set forth in claim 1, further comprising analog-to-digital converters for converting said electrical sound signal and said total sound signal from analog signals to digital signals before said electrical sound signal and said total sound signal are fed to said gain calculator.

7. An audio enhancement system as set forth in claim 6, wherein said first volume control includes a digital to analog converter for converting said electrical sound signal from digital to analog prior to transmission to said loudspeaker.

8. An audio enhancement system as set forth in claim 1, wherein said gain calculator further comprises apparatus for simulating human hearing.

9. An audio enhancement system as set forth in claim 1, wherein said signal processor subtracts said sound output from said total sound signal using adaptive filters.

10. An audio enhancement system as set forth in claim 9, further comprising a decimator for limiting the computational load on said signal processor.

11. An audio enhancement system as set forth in claim 1, wherein said audio signal source comprises a left channel and a right channel and said signal processor comprises at least two adaptive filters, wherein one said adaptive filter removes information from that portion of said total sound signal that corresponds to said left channel and another said adaptive filter removes information from that portion of said total sound signal that corresponds to said right channel.

12. An audio enhancement system as set forth in claim 1, further comprising higher-frequency-pass filters for filtering the portions of said electrical sound signal and said ambient noise signal fed to said gain calculator to reduce the influence of the bass elements of said electrical sound signal and said ambient noise signal on said gain calculator.

13. An audio enhancement system as set forth in claim 1, further comprising a compressor between said audio signal source and said loudspeaker.

14. An audio enhancement system for compensating for ambient noise in a listening environment, comprising

A. an audio signal source for producing an electrical sound signal;

B. a splitter for separating said electrical sound signal into a first component and a second component, said first component being substantially identical in all respects to said second component;

C. a loudspeaker for generating a sound output from said second component of said electrical sound signal;

D. a microphone adapted for placement in a listening environment to provide a total sound signal representative of the total sound level in said environment, wherein said total sound level comprises both said sound output from said loudspeaker and the ambient noise within said environment;

E. an analog-to-digital converter for converting said first component of said electrical sound signal and said total sound signal from analog signals to digital signals;

F. a signal processor for subtracting said sound output from said total sound signal, thereby extracting an ambient noise signal representative of said ambient noise;

G. a gain calculator for comparing said first component of said electrical sound signal with said ambient noise signal; and

H. at least a first volume control responsive to the relative levels of the first component of said electrical sound signal and the ambient noise signal for adjusting said sound output of said loudspeaker to compensate for said ambient noise level.

15. An audio enhancement system as set forth in claim 14, wherein said gain calculator further comprises apparatus for simulating human hearing.

16. An audio enhancement system as set forth in claim 14, wherein said signal processor subtracts said sound output from said total sound signal using adaptive filters.

17. An audio enhancement system as set forth in claim 14, wherein said audio signal source comprises a left channel and a right channel and said signal processor comprises at least two adaptive filters, wherein one said first adaptive filter removes information from that portion of said total sound signal that corresponds to said left channel and another said adaptive filter removes information that portion of said total sound signal that corresponds to said right channel.

18. An audio enhancement system as set forth in claim 16, further comprising a decimator for limiting the computational load on said signal processor.

19. An audio enhancement system as set forth in claim 14, further comprising a higher-frequency pass filter for filtering the portions of said electrical sound signal and said ambient noise signal fed to said gain calculator to reduce the influence of the bass elements of said electrical sound signal and said ambient noise signal on said gain calculator.

20. An audio enhancement system as set forth in claim 14, further comprising a compressor between said audio signal source and said loudspeaker.

21. An audio enhancement system for compensating for ambient noise in a listening environment, comprising

A. an audio signal source for producing an electrical sound signal;

B. a loudspeaker for generating a sound output from said electrical sound signal;

C. a microphone adapted for placement in a listening environment to provide a total sound signal representative of the total sound level in said environment, wherein said total sound level comprises both the sound output from said loudspeaker and the ambient noise within said environment;

D. a splitter for splitting said electrical sound signal from said audio signal source into at least a first and a second electrical sound signal, said first and second electrical sound signals having different frequencies;

E. a signal processor for extracting an ambient noise signal representative of the ambient noise level in said environment from said total sound signal;

F. a gain calculator for comparing said first electrical sound signal with said ambient noise signal and for comparing said second electrical sound signal with said ambient noise signal; and

G. at least one volume control responsive to said gain calculator for adjusting the output of said audio signal source to compensate for said ambient noise level.

22. An audio enhancement system as set forth in claim 21, wherein said gain calculator further comprises apparatus for simulating human hearing.

23. An audio enhancement system as set forth in claim 21, wherein said signal processor subtracts said sound output from said total sound signal using adaptive filters.

24. An audio enhancement system as set forth in claim 23, further comprising a decimator for limiting the computational load on said signal processor.

25. An audio enhancement system as set forth in claim 21, further comprising a high-frequency pass filter for filtering the portions of said electrical sound signal and said ambient noise signal input to said gain calculator to reduce the influence of the bass elements of said electrical sound signal and said ambient noise signal on said gain calculator.

26. An audio enhancement system as set forth in claim 21, further comprising a compressor between said audio signal source and said loudspeaker.

27. An audio enhancement system as set forth in claim 21, further comprising analog-to-digital converters for converting said electrical sound signals and said total sound signal from analog signals to digital signals before said electrical sound signals and said total sound signal are fed to said gain calculator.

28. An audio enhancement system as set forth in claim 27, wherein said first volume control includes a digital to analog converter for converting said electrical sound signal from digital to analog prior to transmission to said loudspeaker.

29. An audio enhancement system as set forth in claim 21, wherein said audio signal source comprises a left channel and a right channel and said signal processor comprises at least two adaptive filters, wherein one said adaptive filter removes information from that portion of said total sound signal that corresponds to said left channel and another said adaptive filter removes information from that portion of said total sound signal that corresponds to said right channel.