Journal of Dental Research, Vol 72, 871-875, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Power spectral analysis of temporomandibular joint sounds in asymptomatic subjects
L. M. Gallo, R. Airoldi, B. Ernst and S. Palla
Abteilung KFS, Zahnarztliches Institut, Zurich, Switzerland.
Very little has been done to quantify temporomandibular joint (TMJ) sound
amplitudes and background noise and to determine the spectrum from healthy
TMJs. Thus, the aim of this study was to record acoustically the sounds
emitted by healthy TMJs with and without mandibular movements, for
determination of baseline spectra. TMJ sounds were recorded bilaterally
from 40 subjects with healthy joints by means of a self-developed recording
system using miniature capacitor microphones inserted into the earpieces of
a medical stethoscope placed in the meatus of the auditory canal. The
recordings were performed without mandibular movements and during three
consecutive opening and closing movements. The signals were
high-pass-filtered at 50 Hz, low-pass-filtered at 2 kHz, and analyzed by
fast Fourier transform computation on a 1024-point window (fs = 5 kHz). The
linearly weighted average baseline spectrum recorded without motion showed
maximum values of 31 dBSPL (sound pressure level) with a standard error of
+2 to -3 dB. The linearly weighted average movement spectrum had a peak of
66 dBSPL at 156 Hz and decreased almost linearly by about 40 dB/decade to
25 dBSPL at 2000 Hz with a standard error of +/- 2 dB. Thus, the TMJ sound
spectrum of mandibular movements in asymptomatic subjects differed at low
frequencies by up to 35 dB from the baseline spectrum in absence of motion.
