Patent ID: 7181402

Claim:
A method for synthetic widening of the bandwidth of voice signals, comprising the following steps: providing a narrowband voice signal at a predetermined sampling rate; carrying out analysis filtering on the sampled voice signal using filter coefficients which are estimated from the sampled voice signal and which result in the bandwidth of the envelope being widened; carrying out residual signal widening on the analysis-filtered voice signal; and carrying out synthesis filtering on the residual-signal-widening voice signal in order to produce a broader band voice signal with the filter coefficients estimated from the sampled voice signal; wherein the filter coefficients for the analysis filtering and for the synthesis filtering are determined by means of an algorithm from a code book which has been trained in advance, and wherein the algorithm for determining the filter coefficients includes: setting up the code book using a hidden Markov model, with each code book entry having an associated state in the hidden Markov model and with a separate statistical model being trained for each state, describing predetermined features of the narrowband voice signal as a function of that state; extracting the predetermined features from the narrowband voice signal to form a feature vector for a respective time period; comparing the feature vector with the statistical models; and determining the filter coefficients on the basis of the comparison result.