On understanding the quality problems of LPC speech

Results of past studies on the quality problems of LPC speech are reviewed. The causes of the quality problems are found to lie within the basic model assumptions as well as inaccuracies in LPC analysis and errors introduced in pitch and voicing detection and parameter quantization. Experiments discussed here show that LPC synthesis is generally very close to natural speech in the high frequency region and that most of the degradation is in the low frequency reglon (approximately less than 1500 Hz).