Experimentation with synthesized speech generated from line-spectrum pairs

Line-spectrum pairs (LSP´s) are frequency-domain parameters similar to formant frequencies. Thus, they have frequency-selective spectral-error characteristics which allow LSP quantization in accordance with auditory perception. In addition, ease of estimating the spectral-error sensitivity of each line spectrum makes possible encoding each line spectrum efficiently. This correspondence, for the first time, demonstrates that a 31 bit representation of LSP´s provides similar intelligibility as a 41 bit representation of reflection coefficients in a current 2400 bit/s LPC. Even with a 12 bit quantization of LSP´s, the loss of speech intelligibility is minor, only 2.4 points below that of a 41 bit quantization of reflection coefficients as measured by the diagnostic rhyme test (DRT) which tests initial-consonant discrimination.