Low-band extension of telephone-band speech

This paper describes a system that generates a low-band signal (100-300 Hz) from a telephone-band (300-3400 Hz) speech signal to obtain an extended-band speech signal (100-3400 Hz). The low-band increases signal naturalness and listening comfort. This system is applied at the receiving end such that compatibility with all current telephone networks is maintained. The described technique splits the telephone-band speech signal into a spectral envelope and a short-term residual. The spectral envelope and the residual are extended separately and recombined to create an extended band signal. This system is evaluated by listening tests and distortion measurement.