Bandwidth Extension of Telephone Speech Using a Filter Bank Implementation for Highband MEL Spectrum
The limited audio bandwidth used in telephone systems degrades both the quality and the intelligibility of speech. This paper presents a new method for the bandwidth extension of telephone speech. Frequency components are added to the frequency band 4 - 8 kHz using only the information in the narrowband speech. First, a wideband excitation is generated by spectral folding from the narrowband linear prediction residual. The highband of this signal is divided into four subbands with a filter bank, and a neural network is used to weight the subbands based on features calculated from the narrowband speech.