Wideband CELP speech coding at 16 kbits/sec

The authors investigate the use of CELP (code excited linear prediction) in coding wideband speech signals at an operating rate of 16 kb/s. The wideband signals under consideration are bandlimited to 7500 Hz and sampled at 16 kHz. In order to achieve a low operating rate, the coding places more emphasis on the lower frequencies (0 to 4 kHz), while the higher frequencies are coded less precisely, but with little perceived degradation. To this effect, the basic CELP model is modified to operate in a split-band mode. For the operating rate of 16 kb/s, subjective tests showed that the wideband speech coder was preferred to a high-quality narrowband coder. This wideband speech coder offers an attractive alternative to conventional narrowband codes at rates near 16 kb/s for many applications