Auditory steady-state responses as neural correlates of loudness growth.

The aim of this study was to find an objective estimate of individual, complete loudness growth functions based on auditory steady-state responses. Both normal-hearing and hearing-impaired listeners were involved in two behavioral loudness growth tasks and one EEG recording session. Behavioral loudness growth was measured with Absolute Magnitude Estimation and a Graphic Rating Scale with loudness categories. Stimuli were sinusoidally amplitude-modulated sinusoids with carrier frequencies of either 500 Hz or 2000 Hz, a modulation frequency of 40 Hz, a duration of 1 s, and presented at intensities encompassing the participants' dynamic ranges. Auditory steady-state responses were evoked by the same stimuli using durations of at least 5 min. Results showed that there was a good correspondence between the relative growth of the auditory steady-state response amplitudes and the behavioral loudness growth responses for each participant of both groups of listeners. This demonstrates the potential for a more individual, objective, and automatic fitting of hearing aids in future clinical practice.