Method and device for spectral expansion for an audio signal
A method and device for automatically increasing the spectral bandwidth of an audio signal including generating a “mapping” (or “prediction”) matrix based on the analysis of a reference wideband signal and a reference narrowband signal, the mapping matrix being a transformation matrix to predict high frequency energy from a low frequency energy envelope, generating an energy envelope analysis of an input narrowband audio signal, generating a resynthesized noise signal by processing a random noise signal with the mapping matrix and the envelope analysis, high-pass filtering the resynthesized noise signal, and summing the high-pass filtered resynthesized noise signal with the input narrowband audio signal. Other embodiments are disclosed.
1. A system, comprising:
a wearable communications device, comprising:
an ambient microphone and an ear canal microphone;
a memory that stores instructions; and
a process that executes the instructions to perform operations, the operations comprising:
generating a mapping matrix, comprising:
simultaneously recording a sentence by the ambient microphone and by the ear canal microphone, wherein the ambient microphone captures a wideband signal and the ear canal microphone captures a narrowband signal;
performing, via the processor, a frequency transform on the wideband signal;
performing, via the processor, another frequency transform on the narrowband signal;
wherein the mapping matrix is based on an analysis of the frequency transform on the wideband signal and the frequency transform on the narrowband signal;
generating an energy envelope analysis of an input narrowband audio signal;
generating a resynthesized noise signal by processing a noise signal with the mapping matrix and the envelope analysis to provide the resynthesized noise signal;
high-pass filtering the resynthesized noise signal to provide a highpass filtered resynthesized noise signal; and
summing the high-pass filtered resynthesized noise signal with the input narrowband audio signal.
2. The system of claim 1 , wherein the operations further comprise providing a signal to output the summed signal via a loudspeaker.
3. The system of claim 1 , wherein providing a single comprises providing the signal via a voice telecommunications system.
4. The system of claim 1 , wherein the ear canal microphone captures a sound exposure level within the ear canal.
5. The system of claim 1 , wherein the mapping matrix is a transformation matrix predicting high frequency energy from a low frequency energy envelope.
6. The system of claim 1 , wherein the frequency transform on the wideband signal transforms the wideband signal into a plurality of bands.
7. The system of claim 1 , wherein the frequency transform on the narrowband signal transforms the narrowband signal into a plurality of bands.
8. The system of claim 1 , wherein summing the high-pass filtered resynthesized noise signal with the input narrowband audio signal increases a spectral range of the input narrowband signal.
9. The system of claim 1 , further comprising an earpiece that occludes an user's ear canal.
10. The system of claim 1 , wherein the wideband signal is a reference wideband signal.
11. The system of claim 1 , wherein the narrowband signal is a reference narrowband signal.
12. A system, comprising:
a memory that stores instructions; and
a process that executes the instructions to perform operations, the operations comprising:
generating a mapping matrix, comprising:
receiving a wideband speech signal from an ambient microphone;
receiving a narrow band signal from a non-microphone source;
performing, via the processor, a frequency transform on the wideband signal;
performing, via the processor, another frequency transform on the narrowband signal;
wherein the mapping matrix is based on an analysis of the frequency transform on the wideband signal and the frequency transform on the narrowband signal;
generating an energy envelope analysis of an input narrowband audio signal;
generating a resynthesized noise signal by processing a noise signal with the mapping matrix and the envelope analysis to provide the resynthesized noise signal;
high-pass filtering the resynthesized noise signal to provide a highpass filtered resynthesized noise signal; and
summing the high-pass filtered resynthesized noise signal with the input narrowband audio signal.
13. The system of claim 12 , wherein the non-microphone source comprises a wireless device.
14. The system of claim 12 , wherein the wireless device provides the narrow band signal encoded via a codec.
15. The system of claim 12 , wherein the operations further comprise outputting the summed signal with an ear canal receiver.
16. The system of claim 12 , wherein the frequency transform on the wideband signal transforms the wideband signal into a plurality of bands.
17. The system of claim 12 , wherein the frequency transform on the narrowband signal transforms the narrowband signal into a plurality of bands.
18. The system of claim 12 , wherein generating a mapping matrix further comprises calculating an energy envelop with a logarithmic dB domain.
19. A system, comprising:
a memory that stores instructions; and
a process that executes the instructions to perform operations, the operations comprising:
generating a mapping matrix, comprising:
receiving a sentence recorded by an ambient microphone and by an ear canal microphone, wherein the ambient microphone captures a reference wideband signal and the ear canal microphone captures a reference narrowband signal;
performing, via the processor, a frequency transform on the reference wideband signal;
performing, via the processor, another frequency transform on the reference narrowband signal;
wherein the mapping matrix is based on an analysis of the frequency transform on the wideband signal and the frequency transform on the narrowband signal;
generating an energy envelope analysis of an input narrowband audio signal;
generating a resynthesized noise signal by processing a noise signal with the mapping matrix and the envelope analysis to provide the resynthesized noise signal;
high-pass filtering the resynthesized noise signal to provide a highpass filtered resynthesized noise signal; and
summing the high-pass filtered resynthesized noise signal with the input narrowband audio signal.
20. The system of claim 19 , wherein the operations further comprise: providing a signal to output the summed signal via a loudspeaker; wherein providing a single comprises providing the signal via a voice telecommunications system.