Abstract
The ultimate goal of objective audiometry is to predict an audiogram in a frequency-specific manner. The frequency specificity of ABR is inadequate to predict hearing accurately in the low frequency range. The auditory steady-state response (ASSR) is elicited by high-frequency tonal stimuli, and its waveform resembles a sinewave. ASSRs elicited by sinusoidally amplitudemodulated (SAM) tones are expected to be an ideal tool for objective audiometry, because of the high frequency specificity of the stimulus tones and because its waveform is suitable for Fourier transform analyses.
When applied to awake adults and detected by phase coherence, the threshold patterns of 40-Hz ASSR closely resemble the corresponding audiogram patterns in all types of hearing impairment. However, the 40-Hz ASSR is not reliable enough to determine the hearing threshold of young children during sleep. The 80-Hz ASSR, however, is clearly detected in young children during sleep by phase coherence, and the threshold patterns of the 80-Hz ASSR resemble the corresponding audiogram patterns. The 80-Hz ASSR therefore appears to be potentially useful for objective audiometry in children.
This paper reviews present knowledge about objective audiometry and ASSR, and techniques for detecting ASSR and its clinical application are discussed.
