关键词: 清/浊音判决, 基音检测, 自相关, 平均幅度差, 门限

Abstract: A new algorithm for U/V decision without threshold and pitch detection is developed on the basis of studying the performance of pitch detection of Auto-Correlation Function（ACF） and Average Magnitude Difference Function（AMDF）.This algorithm obtains the result of U/V decision and the pitch of voiced speech by means of calculating AMDF and ACF of residual signal of LPC（LACF），and comparing the pitch that each method obtains.This algorithm needs only one logical decision and there is no need to compare the threshold.The result of speech coding and decoding simulation，which uses this algorithm by many vocoder，indicates that the U/V decision and pitch detection have a high accuracy and strong noise robustness.

Key words: Unvoiced/Voiced（U/V） dicision, pitch detection, Auto-Correlation Function（ACF）, Average Magnitude Difference Function（AMDF）, threshold