For the purpose of investigating to clarify the differential diagnosis and treatment of TMJ dysfunction, The TMJ sounds were analysed acoustically using accelerometers. The 101 TMJ sounds were recorded from 20 patients. Jaw movement and electromyogram (EMG) were recorded imultaneously. Comparison of the TMJ sounds to the jaw movement and EMG were madse. The following conclusions were obtained: (1) TMJ sounds were classified into three clusters according to the total energy and band width. (2) It is possible to divide the changing of jaw moving velocity into three patterns. (3) It was found that the signal characteristics have relevance to the changing patterns of jaw moving velocity. (4) The acoustical study of TMJ sounds bring on the variable informations to clinical dentistry.
