Binaural loudness summation is not a simple sum of the two ears.

Evidence

Despite presentation of stimuli from one side, the difference in predicted loudness at each unoccluded ear differed by only 4 %. The interaural level difference was small due to the room reverberation. When the left ear was occluded, the predicted loudness at this ear fell by 52 %. Older models assume that binaural loudness is the sum of that for each ear, but more recent models predict less binaural summation by invoking an inhibitory mechanism (Moore and Glasberg 2007 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 1548

Categorization

• DEFINE: Clarifies the conceptual shift from summation models to inhibitory-mechanism models of binaural loudness.
• XREF: Connects to Moore and Glasberg 1996a,b and 2007 loudness models, which also appear in one-eared hearing loss research.