最小编辑距离，可以计算2个字符串的相似度，用于语音文档检索-Minimum edit distance between two strings can calculate the similarity for retrieval of voice files

过零率 (zero-crossing rate,ZCR)是指一个信号的符号变化的比率，例如信号从正数变成负数或反向。 这个特征在语音对比、语音识别和音乐信息检索(music information retrieval)领域得到广泛使用。(Zero-crossing rate (ZCR) refers to the rate at which a signal changes sign, for example, the signal changes from positive to negati