Abstract
A study demonstrating the acquisition of 80-Hz Auditory Steady State Responses (ASSR) from adults elicited using a linear intensity-ramping function is presented. In the typical ASSR testing technique, the stimulus intensity is maintained constant until a response is detected. Testing at individual intensities is repeated until the ASSR threshold is determined. With the present ASSR intensity-ramping technique, the stimulus intensity is changed during the one second stimulus presentation cycle. The stimuli may be composed of a single frequency, multiple frequencies or transients such as clicks presented to one or both ears simultaneously using unique modulation or repetition frequencies for each component and ear. When using a binaural multi-frequency stimulus with the ramping technique, the resulting data not only contains frequency response information but also frequency-specific threshold information in a single recording for both ears. EEG data corresponding to the stimulus presentation cycles are averaged until a pre-specified residual noise level is achieved. Analysis of the recordings is conducted to determine the response onset for each frequency or stimulus component using a Hilbert-transform-based frequency-domain envelope detection filter. The effects on thresholds and frequency specificity of different filter durations are examined. The thresholds are estimated from the response onset time positions using the stimulus time-intensity functions.The ASSR elicited by click stimuli can be utilized for hearing screening as is traditionally done with click-evoked auditory brainstem responses (ABR). In this study the use of binaural click stimuli with time ramping intensity ASSR recordings significantly decreased recording time for threshold detection in hearing screening. For frequency-specific testing, data are collected monaurally for 500, 1000, 2000, and 4000 Hz frequencies in one recording. Validation results for hearing loss from simulations and adult data are also presented. Results from adults indicate reduced testing time and a strong agreement with behavioral thresholds. The ASSR Intensity-Ramping technique is expected to significantly decrease testing time over currently available ASSR testing methods.