Audiometric threshold screening method using envelope detection filters of intensity ramping click auditory steady-state responses

The Auditory Steady-state Responses (ASSR) elicited by click stimuli can be utilized for hearing screening as is traditionally done with click-evoked Auditory Brainstem Responses (ABR). In a typical ASSR or ABR hearing screening, several recordings at different intensities are required to find the response threshold. In this study the use of binaural click stimulus with time ramping intensity produces dual-ear evoked potentials in only one recording session, decreasing significantly the recording time. To achieve this performance a one second sweep consisting of repetitive click stimuli, with logarithmically ramping up intensity, is presented to one or both ears simultaneously. Unique repetition frequencies for each ear are used in order to differentiate the responses coming from each ear. The stimuli sweep is repeated and the EEG data corresponding to each sweep is averaged until a pre-specified residual noise level is achieved. Hilbert-transform-based envelope detection filters in the time domain are used to estimate the signal and noise energy around the main stimulation rate. Because the stimulus time-intensity functions are known, thresholds can be estimated from the response onset time position by estimating the significance of the signal to noise ratio. Preliminary results indicate a strong agreement of the obtained thresholds with behavioral thresholds.