1. Introduction
1. 引言
Zhongwei Shen 沈钟伟

Abstract 摘要
Sound change, as any other change, is a gradual process. The importance of time in the study of sound change has been noted by many linguists. Extensive discussions about the time dimension of sound change can be found in many articles about sound change, e.g., Hoenigswald (1960) and Chen (1972). However, because of the discrete nature of historical documents, very little information about the exact process can really be obtained. In fact, what we learn from these documents are often merely the stages of sound changes: before the change, at various static moments during and after the change. What we cannot learn is the actual workings of a dynamic process which spreads the change from an old form to a new form in a phonological system. Thus the process of sound change therefore is more or less like a black box to us. We can observe what goes in and what comes out from it, but we can never make a direct observation of what is going on inside the black box. It is inevitable that the discussions of the process of sound change are often very abstract and without strong empirical evidence.

It should be obvious that a most interesting aspect of the study of sound change is to explain its internal mechanism. Thus, a better understanding of the process will help us greatly in analyzing various phonological patterns and irregularities observed in historical documents.

1.1 Sound change
1.2 Major hypotheses
1.3 Efforts devoted to solve the controversy
1.4 The existing problems
1.5 The necessity of using numerical methods in the study of sound change