Demonstrations of
Auditory Illusions and Tricks

2nd Edition

Contents Introduction Chapter 1 Chapter 2 Chapter 3 Chapter 4
Chapter 5 Chapter 6 References Archives Demo Index Top Page


I. The Gap Transfer Illusion


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<1> A Long Glide Tone and a Short Glide Tone Crossing Each Other.
A long, ascending glide tone and a short, descending glide tone cross each other.   The ascending tone is 2500 ms in duration, and glides from 422 to 2371 Hz.   The descending tone is 500 ms long, and glides from 1189 to 841 Hz.   The glides cross each other in the middle of the pattern at 1000 Hz and the slope of the glides is about 1 octave/second.   The rise time and the fall time of the short glide are 10 ms and the long glide has a rise and fall time of 500 ms.   A 'bouncing' percept is common in patterns where two components cross each other at the same speed.   The present pattern, however, is often perceived as 'crossing' as a whole, although the long ascending tone of the percept often changes its movement around the crossing point.  

Halpern, L. (1977).
The effect of harmonic ratio relationships on auditory stream segregation.   Unpublished research report, Psychology Department, McGill University.  

Tougas, Y. & Bregman, A.S. (1985).
The crossing of auditory streams.   Journal of Experimental Psychology: Human Perception and Performance, 11, 788-798.  

McPherson, L., Ciocca, V., & Bregman, A.(1994).
Organization in audition by similarity in rate of change: Evidence from tracking individual frequency glides in mixtures.   Perception & Psychophysics, 55, 269-278.  

Fig.01







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<2> A Long Continuous Glide Tone and a Short Disrupted Glide Tone Crossing Each Other
The difference between this pattern and Demonstration <1> is that the short descending glide tone now has a 100 ms gap in the temporal middle.   This pattern is usually perceived veridically.  

Fig.02







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<3> The Gap Transfer Illusion
This demonstration consists of three successive patterns.   First, a short, descending glide tone is presented with a duration of 500 ms and a rise and fall time of 10 ms.   The glide descends from 1189 to 841 Hz, and is perceived as being continuous.   Next, one long, ascending glide tone is presented with a 100 ms gap in the temporal middle.   The longer glide ascends from 422 to 2371 Hz and has a rise and fall time of 500 ms.   In the last pattern, the first two patterns are combined.   The two glides are perceived as crossing each other, but, although physically present in the long glide, the gap is perceived in the middle of the short descending tone.   Despite the difference in the physical location of the gap, the pattern in Demonstration <2> and this pattern are perceived as being similar.  

Nakajima, Y., Sasaki, T., Kanafuka, K., Miyamoto, A., Remijn, G., & ten Hoopen, G. (in press).
Illusory recouplings of onsets and terminations of glide tone components.   Perception & Psychophysics.  

Kanafuka, K., Tanaka, S., Nakajima, Y., & Sasaki, T. (1996).
An illusory transfer of temporal gaps between crossing tones.   Journal of the Acoustical Society of America, 100, 4, 2683.

Fig.03







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<4> A Long Glide Tone and a Short Glide Tone with a Common Gap Crossing Each Other
Two crossing glides with the same features as the glides in Demonstration <1> are presented, but both the long, ascending glide and the short, descending glide have a temporal gap of 50 ms at the crossing point in the middle.   However, the listener perceives a relatively continuous ascending tone.   A clear gap is perceived only in the middle of the short tone.  

Fig.04







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<5> A Long Ascending Glide and Two Short Ascending Glides with a Common Gap
Three ascending frequency glides have a common temporal gap of 40 ms, located in the middle of each glide.   The gap is perceived clearly, but it typically appears as a gap in a short, ascending tone, corresponding to the two short glides.   The long glide is perceived as relatively continuous.   The gap of 40 ms is perceived clearly in the long tone if the short glides are removed.  

Fig.05







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<6> A Long Glide Tone and a Short Glide Tone Crossing Each Other in Opposite Phases
This stimulus pattern is identical with that in Demonstration <1> except that the two components have opposite phases at the crossing points.   Acoustic beats between the two components make a kind of temporal gap of about 40 ms at the crossing point.   This gap, which is common to both components, is often perceived as a gap in the short component, and the long component is perceived as relatively continuous.  

Fig.06

 

 

 

Contents Introduction Chapter 1 Chapter 2 Chapter 3 Chapter 4
Chapter 5 Chapter 6 References Archives Demo Index Top Page