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🪵 The Threshold

Binaural masking level differences reach 25 dB only for overlapping masker and target

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tagsja-picks, xref, question, factual_claims, trade, corroborated, category/definitional-content

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Binaural masking level differences reach 25 dB only for overlapping masker and target

Evidence

The BMLD is a well investigated phenomenon that signifies the reduction in masked thresholds when a tonal signal and masker have disparate interaural cues. For a diotic narrowband masker, a tonal target can be detected at a 25 dB lower level when the interaural target phase is changed from 0 to ∏ (e.g. van de Par and Kohlrausch 1999 ). This large BMLD can only be observed when masker and target are spectrally overlapping. Several studies have shown that the BMLD reduces to rather small values for off-frequency targets (e.g., van de Par et al. 2012 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 3463

In Fig. 15.6, the upper panel illustrates masked threshold as a function of test-tone frequency, fT’ The bandwidth of the masking noise decreases from 100 Hz to 31.6 Hz to 10 Hz from parts (a) to (b) to (c). The BMLDs plotted on the bottom of each part show a maximum at the centre frequency of the noise and decrease as the test-tone frequency deviates from the centre frequency. This is similar to, but more rapid than, the changes in masked threshold and means that the BMLD drops rapidly when masker and signal have no frequency components in common. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1660

It seems that the BMLD increases only slightly as a function of the density level of the masker. BMLDs seem to reach larger values for a bandwidth of 31.6 Hz. Similar effects, although smaller in value, have been found for centre frequencies and test-tone frequencies of 800 Hz. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1653

From the applications of the model, three factors may be added. (1) The well known variability of J N i1T is based on two factors: the variation in JNDL from subject to subject, and the differences in the slope of the inclividual observers’ delay-tuned channels. It may be that these two factors are correlated. (2) BMLDs are conventionally measured in terms of signal level. There are, however, important nonlinearities between the conventional measure and the determining JNDs, i.e. JNDL and J N i1T. However, the effects of varying stimulus parameters on JNDs are reflected sometimes through nonlinearities such that either small differences and/or individual differences can produce what may be often called unusual dependencies. Many of these strange dependencies can be described by the model. (3) The model explains quite clearly that the BMLDs are in fact an improvement in signal-to-masker ratio which consequently leads to a release from masking in frequency and amplitude discrimination. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1707

For a diotic narrowband masker, a tonal target can be detected at a 25 dB lower level when the interaural target phase is changed from 0 to ∏ (e.g. van de Par and Kohlrausch 1999 ). … This large BMLD can only be observed when masker and target are spectrally overlapping. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3463

For a diotic narrowband masker, a tonal target can be detected at a 25 dB lower level when the interaural target phase is changed from 0 to ∏ (e.g. van de Par and Kohlrausch 1999 ). This large BMLD can only be observed when masker and target are spectrally overlapping. Several studies have shown that the BMLD reduces to rather small values for off-frequency targets (e.g., van de Par et al. 2012 ). This lack of a BMLD could be interpreted as a lack of effective binaural processing in off-frequency conditions. Alternatively, it could result from monaural processing which is much better in off-frequency as compared to on-frequency conditions. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3464

Categorization

  • XREF: Connects directly to the reader’s work on binaural processing and psychoacoustics across multiple books in this library. — connects to: Binaural unmasking depends on masker duration but not signal duration — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1636; The BMLD arises from subjects using channels where the masker’s interaural effect is reduced; Signal subtraction after equalization can cancel masking noise in binaural detection (+2 more)
  • QUESTION: The claim that JNDL variation and delay-tuned channel slope differences may be correlated is left unresolved — worth checking whether later work addressed this correlation.
  • corroborated: 7 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 3463; Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1660; Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1653 (+2 more)

Broader Connections

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