The Linguistic Association of Korea Journal, 21(2), 1-20. Recent studies show that Korea stops-the lax and aspirated stop-are undergoing a sound change. This study examines two acoustic parameters-voice onset time (VOT) and fundamental frequency (fo)-to see how their values are diachronically changing (i.e., sound change) and whether there are individual differences in sound change. Acoustic data on VOT values between the lax and aspirated stop are merged whereas f0 differences are maximized to contrast the aspirated and lax onsets. This can be characterized by the loss of a consonantal opposition in terms of VOT and the maximization of a vocalic portion in terms of f0. In addition, there are individual differences in sound change. The result suggest that Korean is still undergoing s sound change and the process of a sound change is analogous to tonogenesis. Further discussion is necessary on how tonogenesis can be applied for explanation of a sound change in Korean.