Method and system of audio power reduction and thermal mitigation using psychoacoustic techniques

• US 9,704,497 B2
• Filed: 07/06/2015
• Issued: 07/11/2017
• Est. Priority Date: 07/06/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Powell, Richard M., Porter, Simon K., Allamanche, Eric A.
• Primary Examiner(s): Yang, Qian
• Application Number:
  US14/792,373
• Publication Number:
  US 20170011748A1
• Time in Patent Office: 736 Days
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 2430/03 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04R 29/001 for loudspeakers H04R29/007 takes precedence
• CPC Class Codes: H04R 3/007 Protection circuits for transducers

Abstract

Method of audio power reduction and thermal mitigation using psychoacoustic techniques starts by receiving a decoded audio signal in a reproduction system. Decoded audio signal is a signal that is decompressed and to be played back by a speaker. A masking curve is generated based on psychoacoustic models and the decoded audio signal. The masking curve is applied to the decoded audio signal to remove unheard frequencies and to generate a power-reduced audio signal. Other embodiments are also described.

Claims

1. A method of audio power reduction and thermal mitigation using psychoacoustic techniques comprising:

receiving a decoded audio signal in a reproduction system;

generating a masking curve based on psychoacoustic models and the decoded audio signal, wherein generating the masking curve includes;

analyzing the decoded audio signal to determine heard frequencies by converting the decoded audio signal from a time domain to a frequency domain, and

generating the masking curve using the decoded audio signal in the frequency domain and the determined heard frequencies;

applying the masking curve to the decoded audio signal to remove unheard frequencies and to generate a power-reduced audio signal; and

playing back the power-reduced audio signal by a speaker in the reproduction system.

2. The method of claim 1, wherein

the decoded audio signal is converted from the time domain to the frequency domain using a first Fast Fourier transform (FFT).

3. The method of claim 2, wherein the first FFT via 1024 points is used to convert the decoded audio signal from the time domain to the frequency domain.

4. The method of claim 1, wherein applying the masking curve further comprises:

applying a second FFT to the decoded audio signal in the time domain to convert the decoded audio signal in the time domain to the frequency domain;

applying the masking curve to decoded audio signal in the frequency domain being output from the second FFT to remove the unheard frequencies and generate a masked signal in the frequency domain; and

applying a third FFT to the masked signal in the frequency domain to convert the masked signal in the frequency domain to the time domain, wherein the masked signal in the time domain is the power-reduced audio signal.

5. The method of claim 4, wherein the second FFT via 512 points is used to convert the decoded audio signal in the time domain to the frequency domain and wherein the third FFT via 512 points is used to convert masked signal in the frequency domain to the time domain.

6. The method of claim 1, wherein generating the masking curve further comprises:

receiving a feedback signal that indicates an audio playback signal level; and

generating the masking curve based on the audio playback signal level.

7. The method of claim 1, wherein generating the masking curve further comprises:

receiving an ambient sensing signal that indicates a reverb level of an environment and a noise level of the environment, wherein the environment is external to the reproduction system and receives a playback of the power-reduced audio signal, and

generating the masking curve based on the ambient sensing signal.

8. The method of claim 1, wherein generating the masking curve further comprises:

receiving a temperature sensor signal that indicates a temperature of a speaker in the reproduction system; and

generating the masking curve based on the temperature of the speaker, wherein the masking curve removes a greater number of unheard frequencies when the temperature of the speaker is above a threshold than when the temperature of the speaker is below the threshold.

9. The method of claim 1, wherein generating the masking curve further comprises:

receiving a power supply signal that indicates a power level of the reproduction system; and

generating the masking curve based on the power level, wherein the masking curve removes a greater number of unheard frequencies when the power level is below a threshold than when the power level is above the threshold.

10. The method of claim 1, further comprising:

amplifying the power-reduced audio signal; and

playing back the amplified power-reduced audio signal by the speaker in the reproduction system.

11. A system for audio power reduction and thermal mitigation using psychoacoustic techniques comprising:

an ear-relevant power reducer that includes a processor;

to receive a decoded audio signal,

to analyze the decoded audio signal to determine heard frequencies, and to convert the decoded audio signal from a time domain to a frequency domain,

to generate a masking curve based on psychoacoustic models and the decoded audio signal, wherein the masking curve is generated using the decoded audio signal in the frequency domain and the determined heard frequencies, and

to apply the masking curve to the decoded audio signal to remove unheard frequencies and to generate a power-reduced audio signal;

an amplifier to amplify the power-reduced audio signal; and

a speaker to playback the amplified power-reduced audio signal.

12. The system in claim 11, wherein

the decoded audio signal is converted from the time domain to the frequency domain using a first Fast Fourier transform (FFT).

13. The system of claim 11, wherein the processor is further:

to apply a second FFT to the decoded audio signal in the time domain to convert the decoded audio signal in the time domain to the frequency domain,

to apply the masking curve to decoded audio signal in the frequency domain being output from the second converter to remove the unheard frequencies and generate a masked signal in the frequency domain, and

to apply a third FFT to the masked signal in the frequency domain to convert the masked signal in the frequency domain to the time domain, wherein the masked signal in the time domain is the power-reduced audio signal.

14. The system of claim 13, wherein the processor is further to:

receive a feedback signal that indicates an audio playback signal level, and

generate the masking curve based on the audio playback signal level.

15. The system of claim 13, wherein the processor is further to:

receive from a sensor external to the system an ambient sensing signal that indicates a reverb level of an environment and a noise level of the environment, wherein the environment is external to the system and receives a playback of the power-reduced audio signal, and

generate the masking curve based on the ambient sensing signal.

16. The system of claim 13, wherein the processor is further to:

receive a temperature sensor signal from a temperature sensor that indicates a temperature of the speaker, and

generate the masking curve based on the temperature of the speaker, wherein the masking curve removes a greater number of unheard frequencies when the temperature of the speaker is above a threshold than when the temperature of the speaker is below the threshold.

17. The system of claim 13, wherein the processor is further to:

receive a power supply signal that indicates a power level of the system; and

generate the masking curve based on the power level, wherein the masking curve removes a greater number of unheard frequencies when the power level is below a threshold than when the power level is above the threshold.

18. A non-transitory computer-readable storage medium having stored thereon instructions, when executed by a processor, causes the processor to perform a method of audio power reduction and thermal mitigation using psychoacoustic techniques comprising:

receiving a decoded audio signal in a reproduction system;

generating a masking curve based on psychoacoustic models and the decoded audio signal, wherein generating the masking curves includes;

analyzing the decoded audio signal to determine heard frequencies by converting the decoded audio signal from a time domain to a frequency domain, and

generating the masking curve using the decoded audio signal in the frequency domain and the determined heard frequencies;

applying the masking curve to the decoded audio signal to remove unheard frequencies and to generate a power-reduced audio signal; and

playing back the power-reduced audio signal via a speaker in the reproduction system.

19. The non-transitory computer-readable storage medium of claim 18, wherein

the decoded audio signal is converted from the time domain to the frequency domain using a first Fast Fourier transform (FFT).

20. The non-transitory computer-readable storage medium of claim 18, wherein applying the masking curve further comprises:

applying a second FFT to the decoded audio signal in the time domain to convert the decoded audio signal in the time domain to the frequency domain;

applying the masking curve to decoded audio signal in the frequency domain being output from the second FFT to remove the unheard frequencies and generate a masked signal in the frequency domain; and

applying a third FFT to the masked signal in the frequency domain to convert the masked signal in the frequency domain to the time domain, wherein the masked signal in the time domain is the power-reduced audio signal.

21. The non-transitory computer-readable storage medium of claim 20, wherein generating the masking curve further comprises:

receiving a feedback signal that indicates an audio playback signal level; and

generating the masking curve based on the audio playback signal level.

22. The computer-readable storage medium of claim 20, wherein generating the masking curve further comprises:

receiving an ambient sensing signal that indicates a reverb level of an environment and a noise level of the environment, wherein the environment is external to the reproduction system and receives a playback of the power-reduced audio signal, and

generating the masking curve based on the ambient sensing signal.

23. The non-transitory computer-readable storage medium of claim 20, wherein generating the masking curve further comprises:

receiving a temperature sensor signal that indicates a temperature of a speaker in the reproduction system; and

generating the masking curve based on the temperature of the speaker, wherein the masking curve removes a greater number of unheard frequencies when the temperature of the speaker is above a threshold than when the temperature of the speaker is below the threshold.

24. The non-transitory computer-readable storage medium of claim 20, wherein generating the masking curve further comprises:

receiving a power supply signal that indicates a power level of the reproduction system; and

generating the masking curve based on the power level, wherein the masking curve removes a greater number of unheard frequencies when the power level is below a threshold than when the power level is above the threshold.

25. The non-transitory computer-readable storage medium of claim 18, having stored thereon instructions, when executed by the processor, causes the processor to perform the method further comprising:

amplifying the power-reduced audio signal; and

playing back the amplified power-reduced audio signal via the speaker in the reproduction system.