社会语言学近期的发展显示了语言变异研究与言语社区理论相结合的趋势,但是对言语社区内部的“一致性”问题还存在着争议。本文介绍的是针对这一问题的一项实证性研究。对北方话鼻韵尾变异现象的定量分析显示:言语社区内部的一致性是相对的和多层次的,一致性是言语社区的存在条件,在某些方面的不一致性恰恰是言语社区层次性的体现。 Recent developments in sociolinguistics show a trend of combining linguistic variation research with speech community theory, but there is still controversy over the issue of “consistency” within speech communities. This article presents an empirical study addressing this issue. Quantitative analysis of the variation of nasal vocal tail in northern dialects shows that consistency within the speech community is relative and multi-level, and consistency is the existence condition of the speech community. In some aspects, the inconsistency is the hierarchical expression of the speech community.