Temporomandibular joint sound is one of the main clinical symptom s of temporomandibular disorders （TMD）. However, it is also present in most asym ptomatic individuals. Because the form ation mechanisms are different, the characteristics of the normal joint sound and different types of TMD joint sound are various. Therefore, we can identify the joint sounds according to the energy, frequency, am plitude and occurring time of the vibration on the joint sound sonogram . And that may be useful to determine the TMJ functional status. In this article，the possible mechanism and research methods of TMJ sound, and the characteristics of sonogram were reviewed.
