Intelligibility control using ambient noise detection

• US 8,744,091 B2
• Filed: 11/12/2010
• Issued: 06/03/2014
• Est. Priority Date: 11/12/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Shaohai, Nicholson, Guy C., Po, Bruce C.
• Primary Examiner(s): Mei, Xu
• Assistant Examiner(s): Jerez Lora, William A
• Application Number:
  US12/945,698
• Publication Number:
  US 20120121096A1
• Time in Patent Office: 1,299 Days
• Field of Search: 381/57, 381/104, 381/106, 381/107, 381/108
• US Class Current: 381/57
• 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: G10L 21/0364 for improving intelligibility
• CPC Class Codes: H04M 1/60 including speech amplifiers

Abstract

A communications device is configured to control the intelligibility of speech in a downlink voice signal during a call. The device determines a current noise level based on sampling ambient acoustic noise and based on a previously determined noise level. The device then determines an overall output gain and a frequency response based on the current noise level and based on a user-selected volume setting of the device. The device modifies the downlink voice signal during the call in accordance with the determined overall output gain and the determined frequency response. Other embodiments are also described and claimed.

Claims

1. A method for modifying intelligibility of speech in a downlink voice signal during a call, comprising:

computing a current noise level estimate based on a) sampling ambient acoustic noise during the call, and b) a previously estimated noise level, by

     1) calculating a delta noise based on the sampled ambient acoustic noise and based on the previously estimated noise level,

     2) determining a slew rate.

     3) calculating a slew delta by multiplying the slew rate and a noise sampling period, and

     4) selecting the sampled ambient acoustic noise to be the current noise level estimate when the delta noise does not exceed the slew delta;

determining an overall output gain based on the current noise level estimate and based on a user-selected volume setting;

determining a frequency response based on the current noise level estimate and based on the user-selected volume setting; and

modifying the downlink voice signal during the call in accordance with the overall output gain and the frequency response.

2. The method of claim 1, wherein the slew rate is variable in that the slew rate is increased when the delta noise is greater than a threshold.

4. The method of claim 1, wherein determining the overall output gain comprises:

determining a gain boost corresponding to the current noise level estimate; and

selecting a volume level from a volume configuration table corresponding to the user-selected volume setting modified by the gain boost.

5. The method of claim 4, wherein determining the overall output gain further comprises:

limiting the gain boost based on the user-selected volume setting.

6. The method of claim 1, wherein determining the frequency response comprises:

determining a pointer offset based on the current noise level estimate;

determining a pointer value corresponding to the user-selected volume setting; and

selecting a set of coefficients from a coefficients list as indicated by the pointer value modified by the pointer offset, the set of coefficients corresponding to the frequency response used for modifying the downlink voice signal.

7. The method of claim 1, wherein modifying the downlink voice signal comprises:

modifying frequency characteristics of the downlink voice signal in accordance with the frequency response; and

modifying an overall gain of the downlink voice signal in accordance with the overall output gain.

3. A method for modifying intelligibility of speech in a downlink voice signal during a call, comprising:

computing a current noise level estimate based on a) sampling ambient acoustic noise during the call and b) a previously estimated noise level, by

     1) calculating a delta noise based on the sampled ambient acoustic noise and based on the previously estimated noise level,

     2) determining a slew rate,

     3) calculating a slew delta by multiplying the slew rate and a noise sampling period, and

     4) selecting the previously estimated noise level plus the slew delta to be the current noise level estimate when the delta noise exceeds the slew delta.

8. An apparatus comprising:

a communications device housing having integrated therein

an acoustic transducer interface circuit coupled to a microphone input to sample ambient acoustic noise,

a processor to sense a user-selected volume setting,

a slew filter circuit having an input coupled to the acoustic transducer interface circuit, the slew filter circuit to compute a current noise level estimate based on the sampled ambient acoustic noise and based on a previously estimated noise level, wherein the slew filter circuit calculates a delta noise between the sampled ambient acoustic noise and the previously estimated noise level, determines a slew rate, calculates a slew delta by multiplying the slew rate and a noise sampling period, limits the current noise level estimate by the previously estimated noise level plus the slew delta whenever the delta noise exceeds the slew delta, and outputs the as-limited current noise level estimate,

a gain boost calculator coupled to the slew filter circuit and the processor, the gain boost calculator to determine an overall output gain based on the current noise level estimate and based on the user-selected volume setting,

a parameter selection circuit to select a volume level from a volume configuration table corresponding to the overall output gain, and to select a set of coefficients from a coefficients list responsive to the current noise level estimate and the user-selected volume setting,

an EQ filter having an input to be coupled to a communications network to receive a downlink voice signal, the EQ filter to modify the downlink voice signal in accordance with the set of coefficients, and

a gain module to modify an overall loudness of the downlink voice signal in accordance with the volume level.

9. The apparatus of claim 8, wherein the slew filter circuit is to vary the slew rate so that the slew rate is increased when the delta noise is greater than a threshold.

10. The apparatus of claim 8, wherein the slew rate is a first constant value for delta noise at or below a first threshold, increases for delta noise between the first threshold and a second threshold, and is a second constant value for delta noise at or above the second threshold.

11. The apparatus of claim 8, wherein the gain boost calculator determines a gain boost based on the current noise level estimate, and outputs the user-selected volume setting plus the gain boost as the overall output gain.

12. The apparatus of claim 11, wherein the gain boost calculator limits the gain boost based on the user-selected volume setting.

13. The apparatus of claim 8, further comprising an EQ boost calculator having an input coupled to the slew filter circuit and the processor, the EQ boost calculator to determine a pointer for the coefficients list based on the current noise level estimate and based on the user-selected volume setting, wherein the EQ boost calculator determines a pointer offset based on the current noise level estimate, determines a pointer value corresponding to the user-selected volume setting, and outputs the pointer value modified by the pointer offset as the pointer for the coefficients list.

14. A method for modifying intelligibility of speech that is in a downlink voice signal during a call, comprising:

repeatedly sampling ambient acoustic noise during the call to obtain a sampled noise sequence;

computing a sequence of current noise level estimates based on the sampled noise sequence, wherein the sequence of current noise level estimates is constrained in that its rate of change is reduced whenever a noise difference between a) a sampled noise level taken from the sampled noise sequence and b) a previously estimated noise level taken from the sequence of current noise level estimates is less than a threshold, and

     2) increased whenever the noise difference is greater than the threshold;

determining an overall gain based on the constrained sequence of current noise level estimates and based on a user-selected volume setting;

determining a frequency response based on the constrained sequence of current noise level estimates and based on the user-selected volume setting; and

modifying the downlink voice signal during the call in accordance with the determined overall gain and the determined frequency response.

15. The method of claim 14, further comprising:

modifying a volume level of artificial background noise produced by a comfort noise generator in accordance with the determined overall gain and the determined frequency response.

16. The method of claim 14, wherein determining the overall gain comprises:

determining a gain boost based on the constrained sequence; and

selecting the overall gain from a volume configuration table corresponding to the user-selected volume setting plus the gain boost.

17. The method of claim 16, wherein determining the overall gain further comprises:

limiting the gain boost based on the user-selected volume setting.

18. The method of claim 14, wherein determining the frequency response comprises:

determining a pointer offset based on the constrained sequence;

determining a pointer value corresponding to the user-selected volume setting; and

selecting a set of coefficients from a coefficients list as indicated by the pointer value modified by the pointer offset, the set of coefficients corresponding to the frequency response used for modifying the downlink voice signal.

19. The method of claim 14, wherein modifying the downlink voice signal comprises:

modifying frequency characteristics of the downlink voice signal in accordance with the frequency response; and

modifying an overall loudness of the downlink voice signal in accordance with the overall gain.

20. The method of claim 14, wherein modifying the downlink voice signal in accordance with the determined frequency response comprises:

increasing gain over a middle frequency band relative to lower and upper frequency bands.

21. An article of manufacture comprising:

a non-transitory machine-readable storage medium having stored therein instructions that program a processor, the processor being a component of a portable communications device, to repeatedly sample ambient acoustic noise during a call to obtain a sampled noise sequence, to compute a sequence of current noise level estimates that is constrained so that its rate of change is a) decreased whenever a noise difference between a sampled noise level and a previously estimated noise level is less than a threshold, and b) increased whenever the noise difference is larger than the threshold, to determine an overall gain based on the constrained sequence and based on a user-selected volume setting, to determine a frequency response based on the constrained sequence and based on the user-selected volume setting, and to modify the downlink voice signal during the call in accordance with the determined overall gain and the determined frequency response.

22. The article of manufacture of claim 21, wherein the processor is to determine the overall gain by determining a gain boost based on the constrained sequence, selecting the overall gain from a volume configuration table corresponding to the user-selected volume setting plus the gain boost, and limiting the gain boost based on the user-selected volume setting.

23. The article of manufacture of claim 21, wherein the processor is to determine the frequency response by determining a pointer offset based on the constrained sequence, determining a pointer value corresponding to the user-selected volume setting, and selecting a set of coefficients from a coefficients list as indicated by the pointer value modified by the pointer offset.

24. The article of manufacture of claim 21, wherein the processor is to modify the downlink voice signal by modifying frequency characteristics of the downlink voice signal in accordance with the frequency response and modifying an overall loudness of the downlink voice signal in accordance with the overall gain.