Improved CELP coding using adaptive excitation codebooks

The authors present a novel method for improving the speech quality of CELP (code excited linear prediction) schemes at low bit rates using an excitation sequence with a locally adapted number of pulses. The design of this adaptive CELP scheme for a data rate of 4.8 kb/s is described. The improvement of the performance as compared to that of a conventional 4.8 kb/s CELP scheme in terms of signal-to-noise ratio is about 3 dB. Due to the significantly reduced roughness, in particular in voiced segments, the processed speech sounds more clear and natural independently of the speaker.<
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