Method and apparatus for distorting a speech signal

Abstract

Method of distorting a speech signal by rearranging and/or reversing frequency bands in this signal. The speech signal is divided into a plurality of sub-bands by filtering, and the sub-bands are individually sampled at a sampling frequencing which is at least double that of the sub-band bandwidth, for providing a plurality of first spectra each with periodic repetition of the respective sub-band. Alternating samples are polarity-reversed for providing a plurality of second spectra each with periodic repetition of the respective sub-band in reversed form. From one of these two types of spectrum a desired sub-band is then filtered out, and corresponds to the original sub-band, but is reversed and/or displaced in the frequency band as desired. All the obtained sub-bands are finally added to send the distorted signal. As an addition to the method of distorting, there is also proposed a method of recomposing the distorted speech signal. Furthermore there is presented an apparatus for distorting or recomposing the speech signal in accordance with the methods.