Demonstrations of
Auditory Illusions and Tricks
2nd Edition
II. The Split-Off
Effect
<7> The Split-Off Effect with Glides
in Different Directions
An ascending tone glide of 1000 ms from 500 to 1000 Hz and a
descending glide of 1000 ms from 800 to 400 Hz are presented
successively with a temporal overlap of 200 ms in the middle.
Thus, the whole duration of the pattern is 1800 ms.
The rise time and the fall time of the glides are 10 ms.
The listener typically perceives one long tone,
which rises and then falls, and a short tone in the middle.
<8> The Split-Off Effect with Glides
in the Same Direction
This pattern consists of two successive glides with a
short overlap. The first glide is 1000 ms and ascends
from 230 to 920 Hz. The second
one is also 1000 ms and ascends from 1080 to 4320 Hz.
The glides overlap each other for 200 ms, making the
total duration of the pattern 1800 ms. The rise time
and fall time of the glides are 10 ms.
The listener often perceives a short tone in the
temporal middle, which does not exist physically.
Sometimes, a long ascending tone covering the whole
duration of the pattern is perceived with this short
tone, but this long tone may be replaced by two
successive ascending tones.
Remijn, G., Nakajima, Y., & ten Hoopen, G.
(in preparation).
The split-off effect and the perception of auditory continuity.
<9> The Split-Off Effect
with Physically Bouncing Components
This pattern was made by separating the lower and higher
components of Demonstration <1> and shifting them in
time and frequency. The lower trajectory consists of a
1300 ms ascending glide tone from 380 to 933 Hz,
immediately followed by a 100 ms descending glide tone
from 933 to 871 Hz. The higher component starts
1100 ms after the beginning of the first component and
consists of a 100 ms descending glide tone from
1148 to 1072 Hz, immediately followed by a 1300 ms
ascending glide tone from 1072 to 2630 Hz.
The difference between the two turning points is 0.2
octave in frequency and 100 ms in time.
The lower component has a rise time of 500 ms and a
fall time of 10 ms, whereas the higher component has
a rise time of 10 ms and a fall time of 500 ms.
The listener often hears a long, continuously ascending
tone and a short, continuously descending tone. Even
though the physical components are 'bouncing', a 'crossing'
percept often appears. It is well known that a physically
crossing pattern can yield a 'bouncing' percept,
yet the present pattern gives a reverse example.
In patterns (b) and (c), turning components are presented
separately.
<10>
The Split-Off Effect with Repetition
This demonstration shows variations of the split-off effect,
which is more stable in repetition than in a one-shot
presentation.
In pattern (a), an ascending glide of 1200 ms with
frequencies of 500 to 2000 Hz, and a descending glide
tone of the same duration from 1500 to 375 Hz
are presented in alternation with overlaps of 200 ms.
The listener perceives a long tone whose pitch rises and
falls in repetition, and alternating high and low short tones.
In pattern (b), an ascending part consists of a
glide tone of 600 ms with frequencies of 500 to 1000 Hz
and another glide tone of the same duration from 1000
to 2000 Hz with an overlap of 200 ms.
This ascending part is immediately followed by a
descending part, which is the mirror image of the
ascending part. The listener perceives a continuous tone
which is rising and falling repeatedly and a short tone in
the middle of each rising and falling part.
<11>
The Split-Off Effect with Repetition with an Additional Glides
In order to mask possible combination tones in the pattern
of the split-off effect, a masking glide tone was added to
the pattern of Demonstration <10b>. For simplicity,
the frequency relationship of Demonstration <10b>
was changed slightly.
Sasaki, T. & Nakajima, Y. (1996).
An illusory reconstruction of auditory elements.
Journal of the Acoustical Society of America, 100, 4, 2751.
