PSYCHOACOUSTIC ADAPTIVE NOTCH FILTERING

• US 20130329909A1
• Filed: 03/08/2013
• Published: 12/12/2013
• Est. Priority Date: 06/08/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krishnaswamy, Arvindh, Ramprashad, Sean A.
• Granted Patent: US 9,386,371 B2
• Time in Patent Office: Days
• US Class Current: 381/94.2
• CPC Class Codes: G10L 21/0324 Details of processing therefor
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S

Abstract

Improved systems and methods for psychoacoustic adaptive notch filtering are provided. By accounting for psychoacoustic properties of an audio signal as well as finer characteristics of noise which may be present in the audio signal (e.g., the shape of the spectral density of the noise), more effective strategies for dealing with undesirable components of the audio signal may be realized.

Claims

1. A method for performing adaptive notch filtering, the method comprising:

receiving an input signal;

determining whether tone-like noise is present in a particular critical band of the input signal; and

in response to a determination that the tone-like noise is present;

estimating an amplitude of the tone-like noise; and

estimating how much energy is contained in the particular critical band;

determining at least one suppression factor for the tone-like noise based on the estimated amplitude and energy;

selecting a notch filter based on the determined at least one suppression factor; and

applying the selected notch filter to the input signal.

2. The method of claim 1, wherein determining whether tone-like noise is present comprises:

applying a predefined notch filter to the input signal to generate a filtered signal.

3. The method of claim 2, wherein determining whether tone-like noise is present further comprises:

calculating a signal power in the filtered signal.

4. The method of claim 3, wherein determining whether tone-like noise is present further comprises:

comparing the calculated signal power with a signal power of the input signal.

5. The method of claim 1, wherein determining at least one suppression factor comprises:

determining at least one notch filter level.

6. A method for performing adaptive notch filtering, the method comprising:

receiving an input signal;

determining how much energy is contained in at least one predefined frequency band of the input signal;

determining a level of tone-like noise present in the at least one predefined band based on the determined amount of energy;

selecting a notch filter based on the determined level; and

applying the selected notch filter to the input signal.

7. The method of claim 6, wherein determining how much energy comprises:

applying at least one band pass filter to the input signal.

8. The method of claim 6, wherein determining the level of tone-like noise occurs only when the determined amount of energy is less than a predetermined amount of energy.

9. The method of claim 6, wherein determining the level of tone-like noise comprises:

applying at least one particular notch filter to the input signal to generate a filtered signal; and

comparing the filtered signal and the input signal.

10. The method of claim 6 further comprising:

determining, prior to selecting, whether suppression of the tone-like noise is required based on the determined level.

11. The method of claim 10, wherein selecting is performed in response to a determination that suppression of the tone-like noise is required.

12. An electronic device comprising:

a receiver configured to receive an input signal, and

an adaptive notch filtering system configured to;

determine how much energy is contained in at least one predefined frequency band of the input signal;

determine a level of tone-like noise present in the at least one predefined band based on the determined amount of energy;

select a notch filter based on the determined level; and

apply the selected notch filter to the input signal.

13. The electronic device of claim 12, wherein the receiver comprises an audio receiver.

14. The electronic device of claim 12, wherein the input signal comprises an audio signal.

15. The electronic device of claim 12, wherein the filtering system comprises a psychoacoustic adaptive notch filtering system.

16. The electronic device of claim 12, wherein the filtering system is configured to determine the amount of energy by applying at least one band pass filter to the input signal.

17. The electronic device of claim 12, wherein the filtering system is configured to determine the level of tone-like noise only when the determined amount of energy is less than a predetermined energy.

18. The electronic device of claim 12, wherein the filtering system is configured to determine the level of tone-like noise by:

applying at least one particular notch filter to the input signal to generate a filtered signal; and

comparing the filtered signal and the input signal.

19. The electronic device of claim 12, wherein, prior to the selection of the notch filter, the filtering system is further configured determine whether suppression of the tone-like noise is required based on the determined level.

20. The electronic device of claim 19, wherein the filtering system is configured to select the notch filter in response to a determination that suppression of the tone-like noise is required.

21. A non-transitory computer readable medium storing a program configured to cause a computer to execute an adaptive notch filtering process, the filtering process comprising:

identifying an input signal;

determining how much energy is contained in at least one predefined frequency band of the input signal;

determining a level of tone-like noise present in the at least one predefined band based on the determined amount of energy;

selecting a notch filter based on the determined level; and

applying the selected notch filter to the input signal.