At the acoustic meatus, where the auditory nerve enters the cranium alongside the vestibular and the facial nerve, the peripheral pathway ends, and the central auditory pathway begins. 'just audible' sound to 'uncomfortably loud'. Since the intensity level at which someone with hearing loss can perceive a sound is elevated compared to someone who doesn't have hearing loss, but the highest tolerable sound intensity hasn't changed, this results in a steeper growth of loudness with intensity. In

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... peracusis, this increase in loudness with intensity is often steeper than in hearing loss alone and can occur without the presence of hearing loss. Previous human and animal neuroimaging studies indicate that hyperacusis is associated with increased cortical and subcortical sound-evoked activity (Gu et al.