Patent ID: 7756714

Claim:
A method in a telecommunication system for extending a spectral bandwidth of a bandwidth limited audio signal (x(n)) having at least one harmonic of a fundamental frequency, the method comprising: applying using a processor a nonlinear function to the bandwidth limited audio signal to generate an extended audio signal x n1 (n), the non-linear function being a quadratic equation: x n1 ( n )= c 2 ( n ) x 2 ( n )+ c 1 ( n ) x ( n )+ c 0 ( n ), the coefficients c 0 , c 1 , c 2 depending on time n, wherein the application of the nonlinear function to the bandwidth limited speech signal results in a first extended speech signal, the coefficients being determined in such a way that c 0 ( n )=− x mit (n−1), c 1 ( n )= K n1,1 − c 2 ( n ) x max ( n ), and c 2 ( n )=( K n1,2 )/( g max x max ( n )+ε), wherein K n1,1 , K n1,2 , g max and ε are predetermined constants, x max (n) is the short time maximum of the absolute value of the bandwidth limited audio signal, and x mit (n) is the short time mean value of the quadratic function.