Relationship between loudness growth function and auditory steady-state response in normal-hearing subjects

The present study investigates the relationship between auditory steady-state responses (ASSRs) and loudness growth function. ASSR amplitudes were compared to the perceived loudness level at frequencies of 500 and 2000Hz in 11 normal-hearing subjects. As a first step, loudness growth function was estimated for the two test frequencies. Then ASSR amplitude was recorded for each of the two frequencies at different stimulus intensities, each corresponding to a loudness level as given by the first part of the study. Normalized results show that the ASSR amplitude correlates well with the loudness function (R(2)=0.81). A stepwise multiple linear regression confirmed these results with loudness explaining almost all the ASSR amplitude (loudness R(2)=0.81, p<0.001, f=562 and for intensity f=1.1, p=0.29). The non-linearity of the ASSR amplitude for low loudness levels can be explained by both the active amplification in the cochlea and the noise in the recording. The results suggest that ASSRs can be used for "objective" loudness measurement.