Dual-mode wideband speech recovery from narrowband speech
Yasheng Qian, P. Kabal · 2003
ABSTRACT: Speech sounds occupy 8 kHz or more of bandwidth. However, current public telephone networks limit the speech bandwidth to 300–3400 Hz. Telephone speech is characterized by thin and muffled sounds, and degraded speaker identification. We describe an algorithm which generates the missing highband components from the narrowband speech signal. The algorithm is based on three acoustic-phonetic classified narrowband-to-wideband linear prediction (LP) spectrum mapping codebooks to recover the missing highband spectrum. Subjective tests show that the reconstructed wideband speech improves the speech quality. LP spectrum bandwidth expansion is used to avoid sharp spectral peaks. The mean SD (log-spectrum distortion) decreases by 0.93 dB, comparing to non-classified codebooks without LP bandwidth expansion.