Frequency-warped audio equalizer
In certain embodiments, an improved audio equalization filter can be generated by frequency warping one or more digital filters having a plurality of frequency bands. Frequency warping can include, for example, transforming at least some of the frequency bands of the one or more digital filters into lower frequency bands. As a result, in various implementations the audio equalization filter may be more accurate than certain currently-available IIR equalization filters. The audio equalization filter may also be more computing-resource efficient than certain currently-available FIR equalization filters.
1. An audio equalization method, the method comprising:
selecting an initial digital filter, the initial digital filter corresponding to a plurality of frequency bands;
frequency warping the initial digital filter to generate an audio equalization filter, the audio equalization filter comprising a finite impulse response (FIR) filter, said frequency warping the initial digital filter comprising applying a plurality of different warping factors to the plurality of frequency bands of the initial digital filter; and
said applying the plurality of different warping factors comprising using a different warping factor for at least two of the plurality of frequency bands of the audio equalization filter, such that the at least two frequency bands of the audio equalization filter are configured to be tunable to separate center frequencies;
wherein the audio equalization filter is configured to filter an input audio signal such that certain frequencies of the input audio signal are selectively adjusted.
2. The audio equalization method of claim 1 , wherein said frequency warping the one or more digital filters comprises transforming at least one of the frequency bands from a higher band to a lower band.
3. The audio equalization method of claim 1 , wherein said frequency warping the one or more digital filters comprises transforming at least one of the frequency bands from a lower band to a higher band.
4. The audio equalization method of claim 1 , further comprising:
adding an additional digital filter to the audio equalization filter, and
creating a new frequency band of the audio equalization filter by at least interpolating between a first frequency band of the additional digital filter and a second frequency band of the audio equalization filter.
5. The audio equalization method of claim 1 , further comprising selecting the warping factors such that said frequency warping causes the at least two frequency bands to be spaced according to a mel scale.
6. The audio equalization method of claim 1 , further comprising selecting the warping factors such that said frequency warping causes the at least two frequency bands to be spaced according to a Bark scale.
7. The audio equalization method of claim 1 , wherein said frequency warping is implemented by one or more processors.
8. A system for equalizing audio, the system comprising:
an audio equalization filter implemented in one or more processors, the audio equalization filter comprising a finite impulse response (FIR) filter, the audio equalization filter configured to be applied to an input audio signal by the one or more processors so as to selectively adjust frequency bands of the input audio signal;
the audio equalization filter being generated from an initial digital filter by at least frequency warping the initial digital filter, said frequency warping comprising applying a plurality of different warping factors to at least some of a plurality of frequency bands of the initial digital filter, the plurality of different warping factors comprising different warping factors for at least two of the plurality of frequency bands, such that the at least two frequency bands of the audio equalization filter are configured to be tunable to separate center frequencies.
9. The system of claim 8 , further comprising a user control configured to provide functionality for a user to adjust the center frequencies of the at least two frequency bands.
10. The system of claim 9 , wherein the user control is configured to adjust at least some of the warping factors responsive to user adjustment of the user control.
11. The system of claim 8 , wherein the audio equalization filter comprises symmetric coefficients.
12. The system of claim 8 , wherein the audio equalization filter is further configured to be frequency warped by at least replacing one or more delay blocks of the initial digital filter with one or more all-pass filter.
13. The system of claim 8 , wherein the audio equalization filter comprises a parametric equalizer.
14. The system of claim 8 , wherein the audio equalization filter comprises a graphic equalizer.