Validity and accuracy of electric response audiometry using the auditory steady-state response: evaluation in an empirical design.

The validity and accuracy of the application of the auditory steady-state response (ASSR) to electric response audiometry (ERA) was tested further in a study permitting subjects to be their own controls for hearing loss. Simulated sensorineural hearing loss (SSHL) of complex configuration and varying degrees was effected using filtered masking noise. Thresholds estimated via ASSR-ERA were compared to those measured via conventional pure-tone audiometry. Further, the slow vertex potential N1-P2 was recorded to permit a comparison with an evoked-response test of common content validity and known accuracy. Results in a homogeneous subject sample demonstrated strong interest correlation and agreement within 10 dB at 1000 to 4000 Hz (on average), but not at 500 Hz. The configurations determined by ASSR-ERA followed behavioral audiometric patterns well, except for the mildest degree of SSHL tested. Consequently, limitations of ERA remain, although ASSR-ERA appears to be quite valid overall and promises (justifiably) broad clinical applicability.

Quantitative description of temporomandibular joint sounds: defining clicking, popping, egg shell crackling and footsteps on gravel.

This study presents a quantitative description of temporomandibular joint (TMJ) sounds provided by a rule-based classification system based on sound classification by three dentists, who listened to and classified the sound recordings as no sound, click, coarse crepitus and fine crepitus. The sounds were recorded with microphones in the ear canal from 126 subjects during vertical opening, digitized at 15 000 Hz, and replayed using a computer sound card and speakers. The dentists' classification of a test set resulted in intra- and inter-tester j values ranging from 0.71 to 0.81 and 0.61-0.73, respectively. Pooled j values for the dentists and the dentists plus the rules were 0.67 and 0.58, respectively, which were not significantly different in terms of the sound features on which the rules were based (P = 0.13). Linear discriminant analysis showed the four TMJ sound types were significantly different (P < 0.001). The performance of the rules was equivalent to the dentists and marginally better than the linear discriminant functions (P = 0.08), establishing the validity of the quantitative descriptions they provide. The recording and rebroadcast methodology produced sounds very similar to those observed in the clinic and could be used to train clinicians in classifying TMJ sounds.