Abstract:On the basis of the methodology that categorizes speech signal into three types,silence,voiceless sound,voiced sound,in view of the random distribution of obvious periodic property speech,the improved algorithm of length varied average magnitude difference function (LVAMDF) and comprehensive multi-factor for pitch frequency detection is put forward to categorize voiced sound into two types,one is obvious periodic property speech,the other one is unobvious periodic property speech. At the same time,the starting and ending points of all accurate pitch period in the obvious periodic property speech is achieved. For a few pitch periods divided into frequency doubling or half frequency,the recognition and correction method is proposed which has a high recognition and correction rate. Finally,in a large amount of the real speech processing experiments,the method can detect the pitch period in the obvious periodic property speech accurately,and there is hardly frequency doubling and half frequency. The results show that the proposed algorithm performs much better on pitch detection compared with AMDF and ACF.