Enhancing the intelligibility of received speech in a noisy environment

• US 7,089,181 B2
• Filed: 01/30/2002
• Issued: 08/08/2006
• Est. Priority Date: 05/30/2001
• Status: Expired due to Fees

• Current Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Original Assignee: Intel Corporation
• Inventors: Erell, Adoram
• Primary Examiner(s): Chawan, Vijay
• Assistant Examiner(s): Opsasnick, Michael N.
• Application Number:
  US10/062,181
• Publication Number:
  US 20030002659A1
• Time in Patent Office: 1,651 Days
• Field of Search: 704224-226
• US Class Current: 704/225
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08
• CPC Class Codes: H03G 7/002 in untuned or low-frequency amplifiers, e.g. audio amplifiers H03G7/007, H03G7/001, H03G7/008, H03G7/02, H03G7/06 take precedence
• CPC Class Codes: H03G 7/007 of digital or coded signals

Abstract

A device receives a signal that includes human-interpretable audio information. The device automatically adjusts the volume of the audio information at the received end. The volume control is determined by an automatic volume control gain, which is calculated as a function of the automatic gain control gain, a weighted dynamic range compression gain, and a weighted constant gain.

Claims

1. A method of controlling volume of a received signal at a near-end device comprising:

receiving a signal originating at a far-end device;

computing an automatic gain control (AGC) gain;

computing a weighted dynamic range compression (DRC) gain;

determining a total automatic volume control (AVC) gain from by combining an additional gain weighted by a previously determined level of ambient noise at the near-end device with the AGC gain and the weighted DRC gain; and

applying the determined AVC gain to adjust speech level and dynamic range in the received signal.

2. The method of claim 1, where the computation of the AGC and DRC gains are performed on a block of speech samples and updated from one block to the next.

3. The method of claim 1, further comprising weighting the DRC gain by the greater of a transmission noise level and the DRC gain factor.

4. The method of claim 1, wherein the additional gain is a constant gain.

5. The method of claim 1, further comprising computing the DRC gain using noise dependent and receive signal independent parameters according to the formula:

drc_gain=MAX_DRC_GAIN*max(drc_gain_factor, noise factor);

wherein MAX_DRC_GAIN is an upper limit on the DRC gain.

6. The method of claim 1, further comprising computing the AGC gain using:

agc_gain=(LEVEL1−

envelope);

wherein LEVEL1 is the target level for a receive signal envelope level;

wherein the computation is limited such that agc_gain=min(MAX_AGC_GAIN, agc_gain);

wherein MAX_AGC_GAIN is the upper limit on the AGC gain and agc_gain=min(MAX_RMS−

long_term_rms, agc_gain), or that the AGC gain is the lesser of the calculated AGC gain and the maximum RMS minus the long term RMS.

7. The method of claim 1, further comprising smoothing the total AVC gain.

8. The method of claim 7, further comprising smoothing over several frames.

9. An apparatus comprising:

a receiver which receives a transmitted signal originating at a far-end device;

a processor which determines an automatic gain control (AGC) gain, a dynamic range compression (DRC) gain, a weighted additional gain based on a level of ambient noise at the near-end device, wherein the processor combines the AGC gain, the DRC gain, and the weighted additional gain to obtain an automatic volume control (AVC) gain; and

a volume control which adjusts a volume of the received signal based on the AVC gain.

10. The device of claim 9, further comprising applying the AVC gain to adjust the volume of the received signal.

11. The device of claim 9, wherein the received signal includes speech.

12. The device of claim 9, wherein the processor weights the DRC gain by the greater of a transmission noise level and the DRC gain factor.

13. The device of claim 9, wherein the additional gain is a constant gain.

14. The device of claim 9, wherein the processor smoothes the AVC gain.

15. A method comprising:

computing an automatic volume control (AVC) gain based on an automatic gain control (AGC) gain, a dynamic range compression (DRC) gain, and a weighted constant gain based on a level of ambient noise at a near-end device; and

adjusting a volume at the receiver based on the AVC gain applied to a signal originating from a far-end device.

16. The method of claim 15, further comprising smoothing the computed AVC gain.

17. The method of claim 15, further comprising decoding speech in a received signal.

18. The method of claim 15, further comprising weighting the DRC gain by the greater of the transmission noise level and the DRC gain factor and weighing the constant gain by the transmission noise level.

19. The method of claim 18, further comprising combining the AGC gain with the weighted DRC gain and the weighted constant gain to obtain the AVC gain.