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 original an input narrowband audio signal. Other embodiments are disclosed.
1. A communication device comprising:
a first microphone configured to generate a first microphone signal;
a second microphone configured to generate a second microphone signal;
a first memory configured to store a prediction matrix, wherein the prediction matrix is generated by analysis of a reference wideband signal previously measured by the first microphone and a reference narrowband signal previously measured by the second microphone;
a second memory configured to store instructions; and
a processor that is configured to execute the instructions to perform operations, the operations comprising:
receiving the second microphone signal;
generating an energy envelope of the second microphone signal;
generating a random noise signal;
generating a resynthesized noise signal using the random noise signal, the prediction matrix and the envelope;
applying a high-pass filter to the resynthesized noise signal to generate a modified noise signal; and
summing the modified noise signal with the second microphone signal to generate a modified second microphone signal.
2. The device according to claim 1 further including the step of:
sending the modified second microphone signal to a second communication device.
3. The device according to claim 2 , wherein the modified second microphone signal includes the voice of a user of the device.
4. The device according to claim 2 , wherein the device is at least one of a phone, a watch, eye glasses, a hearing aid, a steering wheel, or a computer.
5. The device of claim 1 , wherein the prediction matrix is configured to predict high frequency energy from a low frequency energy envelope.
6. The device of claim 1 , wherein the reference wideband and reference narrowband signals are generated from simultaneous recording of s sentence uttered from a user of the device.
7. The device according to claim 1 , wherein the energy envelop of the second microphone signal extends to a frequency of 4 kHz.
8. The device according to claim 1 , where the first microphone is an ambient sound microphone (ASM).
9. The device according to claim 8 , wherein the device further comprises:
a speaker.
10. The device according to claim 8 , wherein the device further comprises:
a user interface.
11. The device according to claim 10 , wherein the user interface is a button, a touch control, or a touch display.
12. The device according to claim 1 , where the second microphone is an ear canal microphone (ECM).
13. The device according to claim 12 , wherein the device further comprises:
a speaker.
14. The device according to claim 12 , wherein the device further comprises:
a user interface.
15. The device according to claim 1 , where the first microphone is an ambient sound microphone (ASM) and the second microphone is an ear canal microphone (ECM).
16. The device according to claim 15 , wherein the device further comprises:
a speaker.
17. The device according to claim 15 , wherein the device further comprises:
a user interface.
18. The device according to claim 1 , further comprising:
a sound isolating component.
19. The device according to claim 18 , where the sound measured by the ECM is on an opposite side of the sound isolating component than the sound measured by the ASM.
20. The device according to claim 18 , wherein the sound isolating component attenuates sound at least an average dB of 30 across frequencies 50 Hz to 10 kHz.