[TMJ clicking sounds and changes in masking level].

Abstract

It is known that the peak distribution of the power spectrum seen in the clicking sounds of the temporomandibular joints appears in the vicinity of 1 KHz in a high rate. Based on the findings that this marginal zone corresponds to speech range, the authors have performed masking experiment by narrow band noise on 20 ears in 10 normal persons and 27 ears in 19 patients with noise as subjects to assess the influence exerted by mechanical stimulation on the condition of hearing ability in speech range. The results in normal persons were 14.8dB (S.D. 13.7) at 500Hz. 27.0dB (S.D. 11.1) at 1,000Hz and 21.3dB (S.D. 10.4) at 2,000Hz. The results in abnormal persons were 12.2dB (S.D. 9.9) at 500Hz, 20.6dB (S.D. 6.6) at 1,000Hz and 15.9dB (S.D. 4.4) at 2,000Hz. A significant difference was observed in the masking level between the two groups at 1,000Hz band with a risk rate of 5%. From the above, it was suggested that the sound constituent of TMJ clicking sound exerts influence on the specific auditory level in the patients with noise.