Binaural unmasking depends on masker duration but not signal duration

Evidence

The results show very clearly that masked thresholds in both conditions depend on test-tone duration. The BMLD, however, which is plotted at the bottom of each panel, does not show any dependence. This occurs whether the test tone is presented at the end of the masker (Fig. 15.2a) or at the beginning of the masker (Fig. 15.2b). The duration of the masker was kept constant at 300 ms. In another experiment, similar conditions were produced, however, the masker duration was varied while the test-tone signal duration was kept constant at 10 ms. The results are indicated on the right side of Fig. 15.2. It shows that the BMLD increases from about 5 to 10 dB as masker duration increases from 10 to 200 ms, regardless of the temporal position of the test-tone burst (shown in the insets of Fig. 15.2c and d). These effects also hold for other frequencies of the test tone although the BMLD becomes smaller for higher frequencies. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1636

The question of interest is whether the effect of eliminating spectro-temporal regions will follow a different course for collocated and spatially separated source configurations. Should a BMLD-like effect indeed act at the level of small spectro-temporal regions, then deletion of target speech from spectro-temporal regions with local SNR values between ‑15 and 0 dB (i.e. between dichotic and diotic masked thresholds, Hirsh ( 1948 )), should degrade speech intelligibility for separated, but not for collocated sources, since those speech components would be inaudible in a collocated configuration anyway. This implies that over this same range of SNR criteria the spatial release from masking, as measured by the difference in performance between separated and collocated source configurations, should decrease. — Dijk, Pim van, Physiology, Psychoacoustics and…, 1626

Categorization

• DEFINE: Clarifies what a BMLD (binaural masking level difference) mechanism would predict for local spectro-temporal deletion — a specific testable prediction.
• XREF: Connects to psychoacoustic masking-level-difference literature (Hirsh 1948) and to spatial release from masking. — connects to: Binaural masking level differences reach 25 dB only for overlapping masker and target — Dijk, Pim van, Physiology, Psychoacoustics and…, 3463; Binaural detection advantages act on small spectro-temporal units, not whole frequency bands
• corroborated: 5 independent passages support this claim — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1636; Dijk, Pim van, Physiology, Psychoacoustics and…, 1626

Broader Connections

• Binaural masking level differences reach 25 dB only for overlapping masker and target #qualifies (0.80) — Dijk, Pim van, Physiology, Psychoacoustics and…, 3463
• Binaural detection advantages act on small spectro-temporal units, not whole frequency bands #expands (0.75)