中文摘要：

彝语属于汉藏语系藏缅语族彝语支，其元音有松紧的对立。本文提取其元音的基频、开商和速度商参数，探讨了松紧对立在语言学中的意义。研究结果显示：（1）在21中主要区别在于发声类型，即紧音属于紧嗓音、松音属于正常嗓音。（2）在33调中，紧音在逐渐变松。（3）松紧音在高平调55调中，紧音处于变异中，有的已经变松，有的未变。（4）松紧元音的区别性特征（开商、速度商和基频）在词汇上体现出词汇的演变和扩散。

英文摘要：

Yi language belongs to the Yi branch of the Tibeto-Burman group in the Sino-Tibetan family, and is noted for the contrast between ＂tense＂ and ＂lax＂ vowels. Analyzing the fundamental frequency （ F0 ） , open quotient （OQ） and speed quotient （SQ） of ＂tense＂ and ＂lax＂ vowels in Yi, this paper presents an acoustic study of the tense-lax contrast and discusses its signi.ficance in linguistics. Preliminary results show that： （ 1 ） on the contour tone of 21, ＂tense＂ is creaky while ＂lax＂ is modal; （2） on tone 33, ＂tense＂ gradually becomes lax; （3） on tone 55, some ＂tense＂ vowels have evolved to be lax, while the others did not do so; （ 4 ） the distinctive features （ F0, OQ, SQ ） of tense/lax voice in Mile Yi shows evolution and diffusion occurring in its lexicon.