Waveform analysis of 40-Hz auditory steady-state response using wavelet analysis

A new design based on wavelet analysis for the objective audiometry devices is proposed. The auditory brainstem response and 80-Hz auditory steady-state response (ASSR) are used in the objective audiometry devices for infants. For the aged, an objective audiometry device is used in anti-aging investigations, which enables the hearing acuity of awake adults to be tested with the 40-Hz ASSR. The ASSR evoked by an amplitude modulated tone is recorded as a waveform. However, the evoked potential response is very small. Therefore, it is difficult to decide a threshold of the response and whether a significant response exists when it is mixed with noise such as the background brain waves. To cope with this problem, we need to average the evoked response waveforms. In particular, the 40-Hz ASSR has a large amount of noise caused by the background brain waves in comparison with the 80-Hz ASSR. In this paper, we apply waveform analysis using the wavelet transform in order to extract the 40-Hz ASSR from a signal mixed with a large amount of noise. Subjects with normal hearing participated in this study.