Method of improving externalization of virtual surround sound
View Patent ↗Aspects of the present disclosure relate to techniques for processing a source audio signal in order to localize sounds. In particular, aspects of the present disclosure relate to sound localization techniques which externalize sounds for headphone audio, such as a virtual surround sound headphone system. In various implementations, room reverberations and other acoustic effects of the environment may be more accurately modeled using improved room reverberation models. For example, in some implementations, the underlying source signal may be filtered with a filter representing a room impulse response that is a combination of a stereo room impulse response and a mono room impulse response. By way of further example, in some implementations the source signal may be filtered with a combined impulse response filter that is derived from binaural recordings of simulated impulses recorded in a desired reverberant environment.
1. A method comprising:
a) generating a signal by filtering a source audio signal having at least one source channel with at least one filter representing at least one room impulse response; and
b) filtering the signal from a) with at least one filter representing at least one head-related impulse response;
wherein each said room impulse response is a crossover combination of a monophonic room impulse response and a stereophonic room impulse response; and
wherein low frequency components of the stereophonic room impulse response of each said room impulse response in the crossover combination are attenuated
c) utilizing the signal to drive a speaker.
2. The method of claim 1 , wherein the monophonic room impulse response and the stereophonic room impulse response are combined in different proportions in different frequency ranges.
3. The method of claim 1 ,
wherein high frequency components of the monophonic room impulse response of each said room impulse response are attenuated.
4. The method of claim 1 ,
wherein each said monophonic room impulse response is generated by recording reverbs in a desired environment using a single microphone in the desired environment and each said stereophonic room impulse response is generated by recording reverbs in the desired environment using two microphones in the desired environment, wherein the two microphones are spaced apart by a distance approximating a distance between a listener's ears.
5. The method of claim 1 ,
wherein said source audio signal has a plurality of source channels;
wherein each said source channel corresponds to a different location;
wherein the at least one head related impulse response is a plurality of head related impulse responses;
wherein the plurality of head related impulse responses includes a pair of head related impulse responses for each said different location.
6. The method of claim 1 , further comprising combining the at least one monophonic room impulse response with the at least one stereophonic room impulse response.
7. The method of claim 1 , further comprising combining the at least one monophonic room impulse response with the at least one stereophonic room impulse response, wherein said combining includes:
filtering the at least one monophonic room impulse response with a low pass filter, and
filtering the at least one stereophonic room impulse response with a high pass filter.
8. The method of claim 1 ,
wherein said filtering the source audio signal with the at least one filter representing the room impulse response and said filtering the audio signal from a) with the at least one filter representing the head-related impulse response includes using an impulse response that simultaneously models both the head-related impulse response and the room impulse response.
9. The method of claim 1 , further comprising generating each said monophonic room impulse response and each said stereophonic room impulse response by recording reverbs in a desired environment.
10. The method of claim 1 ,
wherein said at least one source channel is a plurality of source channels,
wherein each said source channel is a surround sound channel for a speaker of a surround sound format,
wherein the at least one head related impulse response is a plurality of head related impulse responses;
wherein the plurality of impulses responses includes a pair of impulse responses for each said surround sound channel.
11. The method of claim 1 , where said convolving the audio signal from a) with the at least one head-related impulse response includes:
convolving the signal from a) with at least one head-related impulse response which models an impulse coming from a desired source location of a source of the sound signal, and
convolving the signal from a) with at least one head-related impulse response which models an estimated early reflection of a sound from said source location.
12. A system comprising:
a processor;
a memory; and
instructions embodied in the memory an executable by the processor, wherein execution of the instructions by the processor causes the processor to perform a method, the method comprising:
a) generating a signal by filtering a source audio signal having at least one source channel with at least one filter representing a room impulse response; and
b) filtering the signal from a) with at least one filter representing at least one head-related impulse response;
wherein each said room impulse response is a crossover combination of a monophonic room impulse response and a stereophonic room impulse response; and
wherein low frequency components of the stereophonic room impulse response of each said room impulse response in the crossover combination are attenuated
c) utilizing the signal to drive a speaker.
13. The system of claim 12 , wherein the monophonic room impulse response and the stereophonic room impulse response are combined in different proportions in different frequency ranges.
14. The system of claim 12 , further comprising a pair of headphones, wherein the method further includes outputting an output signal resulting from said convolving to said headphones.
15. The system of claim 12 ,
wherein high frequency components of the monophonic room impulse response of each said room impulse response are attenuated.
16. The system of claim 12 , wherein each said monophonic room impulse response and each said stereophonic room impulse response are algorithmically generated synthetic reverbs.
17. The system of claim 12 ,
wherein said source audio signal has a plurality of source channels;
wherein each said source channel corresponds to a different location;
wherein the at least one head related impulse response is a plurality of head related impulse responses;
wherein the plurality of impulses responses includes a pair of impulse responses for each said different location.
18. The system of claim 12 , wherein the method further comprises combining the at least one monophonic room impulse response with the at least one stereophonic room impulse response, wherein said combining includes:
filtering the at least one monophonic room impulse response with a low pass filter, and
filtering the at least one stereophonic room impulse response with a high pass filter.
19. The system of claim 12 ,
wherein said filtering the source audio signal with the at least one filter representing the room impulse response and said filtering the signal from a) with the at least one filter representing the head-related impulse response includes using an impulse response that simultaneously models both the head-related impulse response and the room impulse.
20. The system of claim 12 , wherein the method further comprises generating each said monophonic room impulse response and each said stereophonic room impulse response by recording reverbs in a desired environment.
21. The system of claim 12 ,
wherein said at least one source channel is a plurality of source channels,
wherein each said source channel is a surround sound channel for a speaker of a surround sound format,
wherein the at least one head related impulse response is a plurality of head related impulse responses;
wherein the plurality of impulses responses includes a pair of impulse responses for each said surround sound channel.
22. A non-transitory computer readable medium having processor-executable instructions embodied therein, wherein execution of the instructions by a processor causes the processor to perform a method, the method comprising:
a) generating a signal by filtering a source audio signal having at least one source channel with at least one filter representing a room impulse response; and
b) filtering the signal from a) with a filter representing at least one head-related impulse response;
wherein each said room impulse response is a crossover combination of a monophonic room impulse response and a stereophonic room impulse response; and
wherein low frequency components of the stereophonic room impulse response of each said room impulse response in the crossover combination are attenuated
c) utilizing the signal to drive a speaker.