Binaural loudness summation levels depend strongly on how monaural presentation is achieved.

Evidence

Figure 1 shows that there was a strong effect of the presentation condition (F (2,22) = 22.1, p < 0.001). The summation effect is less than 1 dB in the Loudspeaker condition, in which monaural presentation was achieved by occluding the meatus with one finger, but is 3–6 dB in the Virtual and Dry conditions, in which monaural presentation was achieved by deactivating one earphone. Summation was also significantly smaller using speech than using noise as a source signal (F (1,11) = 5.6, p < 0.05). — Dijk, Pim van, Physiology, Psychoacoustics and…, 1538

Categorization

• DEFINE: Defines the ‘summation effect’ as the measured decibel difference in perceived loudness between monaural and binaural presentation.
• XREF: Relates to loudness summation literature and the physical vs. methodological basis of binaural loudness; connects to psychoacoustics texts on how earphone-coupling and occlusion alter measurements.
• corroborated: 2 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 1538