Occluding one ear in a sound field dramatically reduces binaural loudness summation

Evidence

The lack of summation in the Loudspeaker condition supports the observations made by Cox and Gray ( 2001 ) and by Epstein and Florentine ( 2009 , 2012 ), that, when monaural presentation is achieved by occluding one ear in a sound field, binaural summation can be dramatically reduced. … The lack of summation could have two logical causes. First, there may be some residual sound energy at the occluded ear that is sufficient to maintain its contribution to binaural loudness. Second, there may be some cognitive element which generates loudness constancy through the knowledge that one ear is occluded. — Dijk, Pim van, Physiology, Psychoacoustics and…, 1544

The lack of summation in the Loudspeaker condition supports the observations made by Cox and Gray ( 2001 ) and by Epstein and Florentine ( 2009 , 2012 ), that, when monaural presentation is achieved by occluding one ear in a sound field, binaural summation can be dramatically reduced. The present results demonstrate this phenomenon for the first time using direct comparisons between successive stimuli. Consistent with suggestions that ecological validity is important to the effect, it was a little larger for speech than for noise, but this effect was rather small (0.8 dB). — Dijk, Pim van, Physiology, Psychoacoustics and…, 1545

Categorization

• QUESTION: The cognitive-constancy hypothesis — that merely knowing one ear is occluded preserves binaural loudness — is a striking claim about top-down processing worth chasing in the broader literature.
• XREF: The speech-versus-noise difference implying ecological validity sits with the reader’s interest in how cognition shapes basic auditory perception. — connects to: Binaural loudness exceeds monaural loudness, more so for soft than loud sounds; The brain suppresses equally loud sound in one ear to convey source direction instantly — Eric J. Heller, Why You Hear What You Hear- An…, 2269; Binaural loudness constancy depends on residual low-frequency cues and knowledge of ear occlusion — Dijk, Pim van, Physiology, Psychoacoustics and…, 1562 (+6 more)
• corroborated: 3 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 1544; Dijk, Pim van, Physiology, Psychoacoustics and…, 1545

Broader Connections

• Even small asymmetries between ears reduce binaural summation #corroborates (0.92)
• Loss of externalisation when one earphone is deactivated may boost apparent loudness summation #expands (0.75)