Process and circuit for producing from a speech signal with small bandwidth a speech signal with great bandwidth

摘要

To improve the transmission quality of speech over existing narrow-band communications networks, it is known to measure the frequency-dependent attenuation and to compensate it. Furthermore it is known to amplify low-frequency components of the transmitted speech signal and to raise the pitch of the entire transmitted speech signal. The new process makes it possible also to supplement non-transmitted signal components in the speech signal. Use is here made of the fact that human speech is composed of a limited number of phonemes which can be recognised by a control unit. Depending on the narrow-band phoneme recognised, the broad band phoneme is subsequently read from a memory and the spectral components in the speech signal are supplemented which were previously filtered out by the bandwidth of the transmission path. Furthermore, an adaptation of the amplitude of the supplemented spectral components is further carried out. The process according to the invention and the circuit for carrying out the process can be used wherever a high reduction of the transmission bandwidth is carried out, that is to say in particular in subscriber equipment of a communications network.