An automatic detection and evaluation method of the Erhua(also called r-retroflexion or retrofex suffixation)in the Putonghua proficiency test(PSC)is proposed.Based on the framework of the computer assisted pronunciation evaluation system,the present authors made an in-depth analysis of phonologic rules and acoustic characteristics of the Erhua,and solved the detection and evaluation of the Erhua as a typical classification problem.Then more representative acoustic features were selected and a variety of difierent classification algorithms were used.The results showed that the boosting classification and regression tree(Boosting CART)could make full use of the characteristics of the Erhua,and the classification accuracy was 92.41%.Based on further analysis of the acoustic feature group,it was found that formant,pronunciation confidence and duration were the most important clues of the Erhua,and these clues could effectively realize the automatic detection and evaluation of the Erhua.
