Method and device for spectral expansion for an audio signal

1. A method for automatically expanding a spectral bandwidth of an audio signal comprising the steps of:

a first training step of generating a mapping matrix, by a digital signal processor, the mapping matrix being a transformation matrix to predict high frequency energy from a low frequency energy envelope, the first training step consisting of simultaneously recording a sentence by an ambient microphone and by an ear canal microphone located in an earphone, wherein the ambient microphone captures a reference wideband signal and the digital signal processor performs a frequency transform on the wideband signal, wherein the ear canal microphone captures a reference narrowband signal and the digital signal processor performs a frequency transform on the narrowband signal into a plurality of bands, 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 into a plurality of bands;

generating, by the digital signal processor, an energy envelope analysis of an input narrowband audio signal;

generating, by the digital signal processor, a resynthesized noise signal by processing a random noise signal with the mapping matrix and the envelope analysis;

high-pass filtering, by the digital signal processor, the resynthesized noise signal; and

summing, by the digital signal processor, the high-pass filtered resynthesized noise signal with the input narrowband audio signal to automatically expand the spectral bandwidth of the input narrowband audio signal to produce a summed signal with spectral enhancement;

reproducing by a loudspeaker the summed signal with spectral enhancement.

2. The method of claim 1 , wherein the reference wideband and narrowband signals consist of a simultaneous recording of a phonetically balanced sentence.

3. The method of claim 1 , where the input narrowband audio signal is taken from the ear-canal microphone within the occluded ear canal and located in the earphone.

4. The method of claim 1 , where the input narrowband audio signal is taken from a received speech audio signal in a speech telecommunications system.

5. The method of claim 1 , where the summed signal is directed to a speech telecommunications system.

6. The method of claim 1 , where the summed signal is directed to a voice controlled device.

7. The method of claim 1 , where the mapping matrix is generated from a least squares fit analysis of the reference wideband and reference narrowband signals.

8. The method of claim 1 , where the mapping matrix is generated by a linear regression model, where the input reference wideband signals and reference narrowband signals are first converted to a frequency domain representation using a Fast Fourier Transform, and secondly each frequency band envelope is converted to a decibel domain representation to perform a linear prediction.

9. A non-transitory computer readable medium containing instructions for spectral enhancement, the execution of the instructions by one or more processors of a computer system causing the one or more processors to perform operations comprising:

generating a mapping matrix, the mapping matrix being a transformation matrix to predict high frequency energy from a low frequency energy envelope, generating of the mapping matrix consisting of simultaneously recording of a sentence by an ambient microphone and by an ear canal microphone, wherein the ambient microphone captures a reference wideband signal and the digital signal processor performs a frequency transform on the wideband signal, wherein the ear canal microphone captures a reference narrowband signal and the digital signal processor performs a frequency transform on the narrowband signal into a plurality of bands, 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 into a plurality of bands;

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;

summing the high-pass filtered resynthesized noise signal with the input narrowband audio signal to produce a summed signal with spectral enhancement; and

reproducing by a loudspeaker the summed signal with spectral enhancement.

10. A system for automatically expanding the spectral bandwidth of an audio signal comprising:

one or more processors;

a memory having instructions and being operatively coupled to the one or more processors, the instructions when executed by the one or more processors performs the operations of:

generating a mapping matrix, consisting of simultaneously recording of a sentence by an ambient microphone and by an ear canal microphone, wherein the ambient microphone captures a reference wideband signal and the digital signal processor performs a frequency transform on the wideband signal, wherein the ear canal microphone captures a reference narrowband signal and the digital signal processor performs a frequency transform on the narrowband signal into a plurality of bands, 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 into a plurality of bands;

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 to provide a resynthesized noise signal;

high-pass filtering the resynthesized noise signal to provide a high-pass filtered resynthesized noise signal; and

summing the high-pass filtered resynthesized noise signal with the input narrowband audio signal to provide a wideband signal to produce a summed signal with spectral enhancement;

reproducing by a loudspeaker the summed signal with spectral enhancement.

11. The system of claim 10 , wherein the mapping matrix is a transformation matrix predicting high frequency energy from a low frequency energy envelope.

12. The system of claim 10 , wherein the summing provides the wideband signal as the output to the loudspeaker for reproducing the audio signal with an expanded spectral bandwidth.

13. The system of claim 12 , where the mapping matrix is generated from a least squares fit analysis of the reference wideband signal and reference narrowband signal.

14. The system of claim 12 , where the mapping matrix is generated by a linear regression model, where the input reference wideband signals and reference narrowband signals are first converted to a frequency domain representation providing frequency band envelopes, and secondly each frequency band envelope is converted to a decibel domain representation.

15. The system of claim 10 , wherein the system further includes a smart watch having one or more microphones.

16. The system of claim 10 , wherein the system further includes a set of smart glasses having one or more microphones.

17. The system of claim 10 , wherein the system further includes a mobile phone having one or more microphones.

18. The system of claim 10 , wherein the system further includes a hearing aid having one or more microphones.

19. The system of claim 10 , wherein the system further includes steering wheel having one or more microphones.

20. The system of claim 10 , wherein the system is formed in an earpiece device.