Apparatus and method for producing virtual acoustic sound
In one embodiment, a sound image is generated by applying first and second copies of a first input audio signal to first and second audio channels, respectively, to generate first and second output audio signals for the sound image. Each output audio signal is generated by (1) applying the corresponding copy of the first input audio signal to a corresponding source placement unit (SPU) to generate M delayed, attenuated, and weighted audio signals, A>1; (2) applying each delayed, attenuated, and weighted audio signal to a corresponding eigen filter to generate one of M eigen-filtered audio signals; and (3) summing the M eigen-filtered audio signals to generate the corresponding output signal. In an alternative embodiment, M copies of a first input audio signal are eigen-filtered prior to applying first and second copies of the resulting eigen-filtered signals to first and second audio channels, respectively.
1. A method for generating a sound image, the method comprising:
(a) applying a first input audio signal to a first audio channel to generate a first output audio signal for the sound image; and
(b) applying the first input audio signal to a second audio channel to generate a second output audio signal for the sound image, wherein each output audio signal is generated by:
(1) applying the first input audio signal to a corresponding source placement unit (SPU) to generate M delayed, attenuated, and weighted audio signals, M>1;
(2) applying each delayed, attenuated, and weighted audio signal to a corresponding eigen filter to generate one of M eigen-filtered audio signals; and
(3) summing the M eigen-filtered audio signals to generate the corresponding output signal.
2. The method of claim 1 , wherein:
the first input audio signal is a mono signal corresponding to a single audio source; and
the first and second output audio signals are left and right audio signals.
3. The method of claim 1 , wherein:
step (a) further comprises applying one or more other input audio signals to the first audio channel to generate the first output audio signal; and
step (b) further comprises applying the one or more other input audio signals to the second audio channel to generate the second output audio signal.
4. The method of claim 3 , wherein:
the first and the one or more other input audio signals are mono signals corresponding to different audio sources; and
the first and second output audio signals are left and right audio signals.
5. The method of claim 3 , wherein:
each other input audio signal is applied to a corresponding SPU to generate other delayed, attenuated, and weighted audio signals;
step (2) comprises summing corresponding delayed, attenuated, and weighted audio signals corresponding to the first and one or more other input audio signals to generate the M delayed, attenuated, and weighted audio signals that are applied to the corresponding eigen filters.
6. The method of claim 5 , wherein:
at least one of the first and one or more other input audio signals is applied to J+1 SPUs to generate delayed, attenuated, and weighted audio signals corresponding to (i) the at least one audio signal and (ii) J reflections of the at least one audio signal, J≧1; and
the resulting delayed, attenuated, and weighted audio signals are summed to generate the M delayed, attenuated, and weighted audio signals that are applied to the corresponding eigen filters.
7. The method of claim 1 , wherein:
the first input audio signal is applied to J+1 SPUs to generate delayed, attenuated, and weighted audio signals corresponding to the first audio signal and J reflections of the first audio signal; and
the resulting delayed, attenuated, and weighted audio signals are summed to generate the M delayed, attenuated, and weighted audio signals that are applied to the corresponding eigen filters.
8. The method of claim 1 , wherein each SPU (1) delays and attenuates the first input audio signal and (2) applies M weight factors to the corresponding delayed and attenuated audio signal.
9. An apparatus for generating a sound image, the apparatus comprising:
(a) a first audio channel adapted to receive a first input audio signal and generate a first output audio signal for the sound image; and
(b) a second audio channel adapted to receive the first input audio signal and generate a second output audio signal for the sound image, wherein each audio channel comprises:
(1) a corresponding source placement unit (SPU) adapted to receive the first input audio signal and generate M delayed, attenuated, and weighted audio signals, M>1;
(2) M eigen filters, each adapted to apply eigen filtering to a corresponding delayed, attenuated and weighted audio signal to generate a corresponding eigen-filtered audio signal; and
(3) a summation node adapted to sum the M eigen-filtered audio signals to generate the corresponding output signal.
10. The apparatus of claim 9 , wherein:
step (a) further comprises applying one or more other input audio signals to the first audio channel to generate the first output audio signal; and
step (b) further comprises applying the one or more other input audio signals to the second audio channel to generate the second output audio signal.
11. The apparatus of claim 10 , wherein:
the first and the one or more other input audio signals are mono signals corresponding to different audio sources; and
the first and second output audio signals are left and right audio signals.
12. The apparatus of claim 10 , wherein:
each other input audio signal is applied to a corresponding SPU to generate other delayed, attenuated, and weighted audio signals;
step (2) comprises summing corresponding delayed, attenuated, and weighted audio signals corresponding to the first and one or more other input audio signals to generate the M delayed, attenuated, and weighted audio signals that are applied to the corresponding eigen filters.
13. The apparatus of claim 12 , wherein:
at least one of the first and one or more other input audio signals is applied to J+1 SPUs to generate delayed, attenuated, and weighted audio signals corresponding to (i) the at least one audio signal and (ii) J reflections of the at least one audio signal, J≧1; and
the resulting delayed, attenuated, and weighted audio signals are summed to generate the M delayed, attenuated, and weighted audio signals that are applied to the corresponding eigen filters.
14. The apparatus of claim 9 , wherein:
the first input audio signal is applied to J+1 SPUs to generate delayed, attenuated, and weighted audio signals corresponding to the first audio signal and I reflections of the first audio signal; and
the resulting delayed, attenuated, and weighted audio signals are summed to generate the M delayed, attenuated, and weighted audio signals that are applied to the corresponding eigen filters.
15. A method for generating a sound image, the method comprising:
(a) applying a first input audio signal to M eigen filters to generate M eigen-filtered audio signals, M>1;
(b) applying the M eigen-filtered audio signals to a first audio channel to generate a first output audio signal for the sound image; and
(c) applying the M eigen-filtered audio signals to a second audio channel to generate a second output audio signal for the sound image, wherein each output audio signal is generated by applying the M eigen-filtered audio signals to a corresponding source placement unit (SPU) to generate the corresponding output signal as a weighted, summed, delayed, and attenuated version of the M eigen-filtered audio signals.
16. The method of claim 15 , wherein:
the first input audio signal is a mono signal corresponding to a single audio source; and
the first and second output audio signals are left and right audio signals.
17. The method of claim 15 , wherein each output audio signal is generated by:
(I) applying the M eigen-filtered audio signals to J+1 SPUs corresponding to the first input audio signal and J reflections of the first input audio signal, J≧1; and
(ii) combining the outputs of the J+1 SPUs.
18. The method of claim 15 , wherein each SPU (1) applies M weight factors to the M eigen-filtered audio signals to generate M weighted, eigen-filtered audio signals and (2) sums, delays, and attenuates the M weighted, eigen-filtered audio signals to generate the corresponding output signal.
19. An apparatus for generating a sound image, the apparatus comprising:
M eigen filters adapted to generate M eigen-filtered audio signals based on a first input audio signal, M>1;
a first audio channel adapted to receive the M eigen-filtered audio signals and generate a first output audio signal for the sound image; and
a second audio channel adapted to receive of the M eigen-filtered audio signals and generate a second output audio signal for the sound image, wherein each audio channel comprises a corresponding source placement unit (SPU) adapted to generate the corresponding output signal as a weighted, summed, delayed, and attenuated version of the M elgen-filtered audio signals.
20. The apparatus of claim 19 , wherein each output audio signal is generated by:
(i) applying the M eigen-filtered audio signals to J+1 SPUs corresponding to the first input audio signal and J reflections of the first input audio signal, J≧1; and
(ii) combining the outputs of the J+1 SPUs.