Build-up of auditory stream segregation induced by tone sequences of constant or alternating frequency and the resetting effects of single deviants

Abstract

Three experiments investigated the dynamics of auditory stream segregation. Experiment 1 used a 2.0-s constant-frequency inducer (10 repetitions of a low-frequency pure tone) to promote segregation in a subsequent, 1.2-s test sequence of alternating low- and high-frequency tones. Replacing the final inducer tone with silence reduced reported test-sequence segregation substantially. This reduction did not occur when either the 4th or 7th inducer was replaced with silence. This suggests that a change at the induction/test-sequence boundary actively resets build-up, rather than less segregation occurring simply because fewer inducer tones were presented. Furthermore, experiment 2 found that a constant-frequency inducer produced its maximum segregation-promoting effect after only three tone cycles—this contrasts with the more gradual build-up typically observed for alternating sequences. Experiment 3 required listeners to judge continuously the grouping of 20-s test sequences. Constant-frequency inducers were considerably more effective at promoting segregation than alternating ones; this difference persisted for ~10 s. In addition, resetting arising from a single deviant (longer tone) was associated only with constant-frequency inducers. Overall, the results suggest that constant-frequency inducers promote segregation by capturing one subset of test-sequence tones into an on-going, pre-established stream and that a deviant tone may reduce segregation by disrupting this capture.

Speech intelligibility in rooms: Disrupting the effect of prior listening exposure

“…Subsequent studies have shown that breakdown can also result from other changes, such as the relative delay between source and echo (Clifton et al,1994), and changes to source/echo spectral characteristics (McCall et al, 1998). It has also been shown with auditory streaming that sudden changes in the stimulus presentation can cause a resetting, or breakdown, of the buildup of segregation (Haywood and Roberts, 2013;Roberts et al, 2008;Bregman, 1993, 1998). To the extent that room exposure effects on speech understanding are related to the precedence effect and/or auditory object formation/streaming, one might expect to find similar evidence of breakdown following abrupt changes to the room acoustic environment.…”

The dynamics of auditory stream segregation: Effects of sudden changes in frequency, level, or modulation

“…No difference was anticipated between the two base frequencies (0.5 kHz and 1 kHz) because both fell within the frequency range for which the ratio ∆f over base frequency at the border between one-and two-stream percepts is roughly constant (Miller and Heise, 1950). All conditions elicited broadly similar patterns of build-up-an initial phase (up to ~10-12 s) that was relatively fast followed by a slower phase (Anstis and Saida, 1985;Haywood and Roberts, 2013;Rajasingam et al, 2018). In general, an increase in ∆f tended to increase both the rate and final extent of build-up.…”

“…They were asked to avoid listening actively for either integration or segregation, but simply to report which of the two percepts they heard at that moment; on occasions when the percept was ambiguous, listeners were asked to report the more dominant (cf. Haywood and Roberts, 2013;Rajasingam et al, 2018). At the end of each trial, there was a 5-s pause before listeners could initiate the next trial.…”

“…Owing to the small number of trials meeting this criterion for the 0-1 s time bin, responses made during that interval were used only in the context of calculations involving subsequent time bins; the 0-1 s time bin was excluded from all further analysis and graphical representation (cf. Haywood and Roberts, 2013;Rajasingam et al, 2018).…”

“…The experiments reported here used tone sequences whose properties were changed at one or more time points and for which the consequences of those changes were tracked over time (cf. Haywood and Roberts, 2013;Rajasingam et al, 2018).…”