Computationally efficient multi-resonator reverberation
View Patent ↗A signal processor to produce a simulated reverberation effect based on an input signal and conveying the impression of multiple interconnected resonating spaces. A feedback delay network produces a reverberation tail signal, which is delayed by varying amounts in a delay module. A panning module produces a multi-channel signal based on the reverberation tail signal and its echoes.
1. A signal processor comprising:
a feedback delay network (“FDN”) having an input to receive an audio signal and an output to produce an exponentially-decaying reverberation tail signal based on the audio signal;
a delay module having an input coupled to the output of the FDN to receive the exponentially-decaying reverberation tail signal and produce therefrom a plurality of variously-delayed versions of the exponentially-decaying reverberation tail signal, the plurality of variously-delayed versions of the exponentially-decaying reverberation tail signal hereinafter referred to as a plurality of reverberation tail echo signals; and
a panning module having a first input coupled to receive the audio signal, a second input coupled to the FDN to receive the exponentially-decaying reverberation tail signal, and a plurality of third inputs coupled to the delay module to receive the plurality of the reverberation tail echo signals, the panning module configured to produce therefrom a plurality of signal channels, the plurality of the signal channels being subsequently combined into a single encoded signal for reproduction on a multi-channel audio system.
2. The signal processor of claim 1 , further comprising:
the panning module to direct the single encoded signal to speakers in a speaker array.
3. The signal processor of claim 1 , further comprising:
a filter module configured to adjust a spectral composition of at least one of the exponentially-decaying reverberation tail signal and the plurality of the reverberation tail echo signals.
4. The signal processor of claim 1 wherein the FDN produces a plurality of exponentially-decaying reverberation tail signals, at least two of the plurality of the exponentially-decaying reverberation tail signals being decorrelated, and at least one of the plurality of the exponentially-decaying reverberation tail signals being received by the delay module.
5. The signal processor of claim 1 wherein the FDN comprises:
a plurality of delay lines configured to produce a plurality of variously-delayed versions of the audio signal; and
a matrix transformer configured to apply a matrix transformation to a vector including the variously-delayed versions of the audio signal and produce a plurality of decorrelated exponentially-decaying reverberation tail signals, one of the decorrelated exponentially-decaying reverberation tail signals being used as the input to the delay module, wherein
a matrix of the matrix transformation is one of a Hadamard matrix and a Fourier matrix.
6. A non-transitory computer-readable medium containing instructions and data to cause a programmable processor to perform operations comprising:
generating, at a feedback delay network, a diffuse simulated reverberation signal based on an input audio signal;
preparing, at a delay module coupled to the feedback delay network, a plurality of reverberation tail echo signals comprising variously-delayed versions of the diffuse simulated reverberation signal based on the diffuse simulated reverberation signal; and
encoding, in a panning module coupled to the feedback delay network and the delay module, the audio signal, the diffuse simulated reverberation signal, and the plurality of the reverberation tail echo signals into a composite signal for a multi-channel reproduction system.
7. The non-transitory computer-readable medium of claim 6 , containing additional instructions and data to cause the programmable processor to perform operations comprising:
filtering the plurality of the reverberation tail echo signals.
8. The non-transitory computer-readable medium of claim 6 , containing additional instructions and data to cause the programmable processor to perform operations comprising:
adjusting a level of one of the plurality of the reverberation tail echo signals based on a spatial relationship between a source of the input audio signal and a listener.
9. The non-transitory computer-readable medium of claim 6 , containing additional instructions and data to cause the programmable processor to perform operations comprising:
adjusting a delay of one of the plurality of the reverberation tail echo signals based on a spatial relationship between a source of the input audio signal and a listener.
10. The non-transitory computer-readable medium of claim 6 wherein generating the diffuse simulated reverberation signal comprises:
producing a plurality of differently-delayed versions of the input audio signal;
applying a matrix transformation to the differently-delayed versions of the input audio signal; and
feeding outputs of the matrix transformation back into the input audio signal; wherein
one of the outputs of the matrix transformation is the diffuse simulated reverberation signal.
11. The non-transitory computer-readable medium of claim 10 wherein a matrix of the matrix transformation is one of a Hadamard matrix and a Fourier matrix.
12. A system comprising:
a simulated environment containing a plurality of resonators;
a simulated sound source located at a predetermined distance from a listener in the simulated environment; and
an audio signal processor, to produce a composite signal according to an input audio signal from the simulated sound source, comprising:
a feedback delay network (“FDN”) having an input to receive the input audio signal from the simulated sound source as an audio signal and an output to produce an exponentially-decaying reverberation tail signal based on the audio signal;
a delay module having an input coupled to the output of the FDN to receive the exponentially-decaying reverberation tail signal and based thereon to produce a plurality of reverberation tail echo signals comprising a plurality of variously-delayed versions of the exponentially-decaying reverberation tail signal; and
a panning module having a first input coupled to receive the audio signal, a second input coupled to the FDN to receive the exponentially-decaying reverberation tail signal, and a plurality of third inputs coupled to the delay module to receive the plurality of the reverberation tail echo signals, the panning module configured to combine the audio signal, the exponentially-decaying reverberation tail signal, and the plurality of the reverberation tail echo signals, the panning module producing, and having an output to transmit, a multi-channel signal as the composite signal based on the combination of the audio signal, the exponentially-decaying reverberation tail signal, and the plurality of the reverberation tail echo signals.
13. The system of claim 12 wherein one of the resonators is a tunnel.
14. The system of claim 12 wherein one of the resonators is a parking structure.
15. The system of claim 12 wherein one of the resonators is a valley.
16. The system of claim 12 wherein one of the resonators is a street with tall buildings.
17. The system of claim 12 wherein the simulated sound source is a motorcycle engine.
18. The system of claim 12 wherein the simulated sound source is a gunshot.
19. The system of claim 12 wherein the simulated sound source is a siren.