Patent ID: 11961529
Assignee: PURDUE RESEARCH FOUNDATION
Field: Computer technology (Electrical engineering)
Classification: CPC G  H | IPC G

Claim 11:
12. A method of audio signal processing comprising:
(a) classifying an audio signal input, which includes a frica ion high-frequency speech energy, into two or more speech sound classes by:
A) comparing a band-pass filtered energy of the audio signal input to a high-pass filtered energy of the audio signal input via a digital signal processor;
B) selecting a form of an input-dependent frequency remapping function based on the comparison of the band-pass filtered energy and the high-pass filtered energy, wherein the form of the input-dependent frequency remapping function is at least one of:
(i) compressive in the mid frequencies and expansive in the high frequencies, or
(ii) expansive in the mid frequencies and compressive in the high frequencies; and

C) selecting an expansive compression ratio (ECR) based on the selected form of input-dependent frequency remapping function;

(b) upon classifying the audio signal input into two or more speech sound classes, initiating a Hybrid Expansive Frequency Compression (hEFC) comprising a re-coding of one or more input frequencies of the speech sound via the input-dependent frequency remapping function to generate one or more output frequencies, wherein the output frequencies are at least one of:
(A) first compressive and then expansive, or
(B) first expansive and then compressive; and

(c) generating an output signal from the output frequencies, wherein the output signal is a representation of the audio signal having a decreased sound frequency.