Binaural sound localization using a formant-type cascade of resonators and anti-resonators
This invention is a method for binaural localization using a cascade of resonators and anti-resonators to implement an HRTF (head-related transfer function). The spectrum of the cascade reproduces the magnitude spectrum of a desired HRTF. The proposed method provides a considerably more computationally efficient implementation of HRTF filters with no detectable deterioration of output quality while saving memory when storing a large quantity of HRTFs due to the parameterization of its resonators and anti-resonators. Finally, the method offers additional flexibility since the resonators and anti-resonators can be manipulated individually during the design process, making it possible to interpolate smoothly between HRTFs, reduce spectral coloring or achieve higher accuracy at perceptually relevant frequency regions. These HRTF are useful in stereo enhancement and multi-channel virtual surround simulation.
1. The method of multi-channel surround sound simulation comprising the steps of:
selectively reverberating a front left channel and a front right channel;
forming a head related transfer function of a front center channel;
selectively reverberating a surround left channel and a surround right channel;
summing the selectively reverberated front left channel with the selectively reverberated surround left channel thereby forming a first left sum;
summing the first left sum and the head related transfer function of the front center channel thereby forming a second left sum;
summing the selectively reverberated front right channel with the selectively reverberated surround right channel thereby forming a first right sum;
summing the first right sum and the head related transfer function of the front center channel thereby forming a second right sum; and
canceling cross talk between the second left sum and the second right sum to produce a left channel simulation signal and a right channel simulation signal.
2. The method of claim 1 , wherein:
said step of forming a head related transfer function includes performing a cascade of at least one resonator and/or anti-resonator.
3. The method of claim 1 , wherein:
each step of selectively reverberating includes
providing at least one delay of a left channel input;
selectively attenuating each at least one delay of the left channel input;
summing the selectively attenuated at least one delay of the left channel input thereby forming a first sum signal;
forming a first head related transfer function of the first sum signal relative to a listener's left ear;
forming a second head related transfer function of the first sum signal relative to a listener's right ear;
providing at least one delay of a right channel input;
selectively attenuating each at least one delay of the right channel input;
summing the selectively attenuated at least one delay of the right channel input thereby forming a second sum signal;
forming a third head related transfer function of the second sum signal relative to a listener's right ear;
forming a fourth head related transfer function of the second sum signal relative to a listener's left ear;
summing said first and fourth head related transfer functions thereby forming a third sum;
summing said third sum and the left channel input thereby forming a left channel output;
summing said second and third head related transfer functions thereby forming a fourth sum; and
summing said fourth sum and the right channel input thereby forming a right channel output.
4. The method of claim 1 , wherein:
each step of forming a head related transfer function includes performing a cascade of at least one resonator and/or anti-resonator.
5. The method of claim 1 , wherein:
said at least one delay of the left input channel differs from said at least one delay of the right channel input.
6. The method of claim 1 , wherein:
said step of providing at least one delay of a left channel input consists of providing a cascade of a plurality of delays; and
said step of providing at least one delay of a right channel input consists of providing a cascade of plurality of delays.
7. The method of claim 6 , wherein:
said step of selectively attenuating each at least one delay of the left channel input includes attenuating each of said plurality of delays; and
said step of selectively attenuating each at least one delay of the right channel input includes attenuating each of said plurality of delays.
8. The method of claim 1 , wherein:
said step of summing said third sum and the left channel input includes weighting the left channel input by a first weighting factor and weighting said third sum by a second weighting factor; and
said step summing said fourth sum and the right channel input includes weighting the right channel input by said first weighting factor and weighting said fourth sum by said second weighting factor.