Time frequency distributions of TMJ sounds.
For analysis of time-varying signals such as the TMJ sounds, it is often desirable to know how the frequency components change with time, using methods of time-frequency analysis. The aim of this study was to compare two of the most familiar methods for energy density representation with a newly developed technique. The sounds were recorded with a microphone fastened to the subject's forehead, transformed to the time-frequency domain and displayed as 3D- and contour plots using spectrogram, Wigner distribution (WD), and the reduced interference distribution (RID) to display their time-frequency energy distributions. The spectrogram resolved only the low-frequency components. The WD provided higher resolution but also exhibited strong interference between components. The RID gave a detailed representation of the TMJ signals' relative energy distribution in the time and frequency domains, with a great reduction in the interference or cross terms. The RID therefore appears to be most useful in the application of time-frequency distributions in classification of TMJ sounds.
Widmalm
S E
SE
Department of Cariology and General Dentistry, University of Michigan, Ann Arbor.
Williams
W J
WJ
Zheng
C
C
D000703:Analog-Digital Conversion; D003626:Data Display; D006801:Humans; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013704:Temporomandibular Joint / Q000502:physiology*; D013997:Time Factors; D014732:Vibration