Loudness summation shrinks dramatically for real-world external sound sources

Evidence

Cox and Gray ( 2001 ) collected loudness ratings (7 categories from “very soft” to “uncomfortable”) for speech at different sound levels when listening monaurally and binaurally. These two modes of listening were compared by using either one or two earphones and, using a loudspeaker, by occluding one ear with a plug and ear muff. They found that results with one or two earphones produced a conventional loudness summation effect, whereby the mean rating was substantially higher at each sound level for binaural presentation. However, when listening to an external source in the environment (the loudspeaker) there was much less summation effect: occlusion of one ear had little effect on the loudness ratings compared to listening binaurally. This experiment showed for the first time that the loudness of external sounds may display constancy across monaural and binaural listening modes. — Dijk, Pim van, Physiology, Psychoacoustics and…, 1528

Categorization

Category: Contrarian or Surprising Claims

• QUESTION: What physical/acoustic mechanism explains why earphone-presented sound summations binaurally but external loudspeaker sound does not? Some real-world binaural cue must be operating.
• CANDY: Plug one ear with a finger while someone talks to you — most people report no change in loudness. Simple, demonstrable, elevator-conversation worthy.

Related

• External real-world sounds show loudness constancy across one and two ears (similarity 0.96)
• Loss of externalisation when one earphone is deactivated may boost apparent loudness summation (similarity 0.90)
• Occluding one ear in a sound field dramatically reduces binaural loudness summation (similarity 0.89)
• A finger in the ear enables rapid 2-interval monaural-binaural loudness comparison (similarity 0.88)
• Binaural loudness constancy operates independently of stimulus type (similarity 0.88)
• Binaural loudness summation shrinks dramatically when one ear is occluded in a sound field. (similarity 0.88)
• Binaural loudness may exhibit constancy across conditions (similarity 0.87)
• Occlusion-based monaural hearing dramatically reduces binaural loudness summation. (similarity 0.86)
• Loudness constancy requires ecologically valid, multisensory real-world stimuli (similarity 0.86)
• Binaural loudness exceeds monaural loudness, more so for soft than loud sounds (similarity 0.86)
• Loudness constancy occurs regardless of whether sound is speech or noise (similarity 0.86)
• Knowledge that an ear is covered reduces loudness summation (similarity 0.86)
• Finger occlusion of one ear leaves perceived loudness of real external sounds nearly unchanged (similarity 0.86)
• Binaural loudness summation levels depend strongly on how monaural presentation is achieved. (similarity 0.86)
• Residual sound at an occluded ear mediates part of loudness constancy (similarity 0.85)