Preaspiration in the Nordic Languages: Synchronic and Diachronic ...

in discharge rates in the auditory nerve does not translate into a threefold
increase in auditory salience.
The third criticism of Bladon’s account concerns the principle of
on/off response asymmetry. As support for this principle, Bladon refers
to a study by Tyler et al. (1982), but it appears that their findings are inappropriately
applied to the principle. In their experiment, Tyler et al.
attempted to establish: a) the smallest perceivable durational differences
(i.e., durational difference limens) of silence in noise; and b) the smallest
perceivable durational differences of noise in silence. The silences, or
gaps, were embedded in 1000-ms noise bursts. The minimal duration of
the gaps was 80 ms, and the total duration of gap and noise burst was
kept constant at 1000 ms. Subjects were presented with three stimuli at a
time with differing gap durations and were asked to identify the longest
gap. For the detection of noise in silence, noise bursts were used. The
shortest noise bursts were 30 ms long. The subjects’ task was to identify
the longest of three noise bursts. Tyler et al. found that “Filled intervals
[noise bursts in silence] are about three times easier to discriminate than
unfilled intervals [gaps in noise]” (1982:745).
There are several problems in translating these findings into a principle
of audition. In accordance with Weber’s Law, durational difference
limens increase as the duration of the stimulus increases. This means that
it is easier to detect a 15 ms difference in duration between two relatively
short stimuli (say 15 and 30 ms) than it is to detect a 15-ms difference
between two relatively long stimuli (say 85 and 100 ms). Since the noise
bursts and the gaps in the experiment of Tyler et al. are not of comparable
durations, their claim that sensitivity to differences in noise burst
duration is greater than sensitivity to differences in gap duration may
partly be a result of the fact that the gaps in their experiment were longer
than the noise bursts. Additionally, Formby and Sherlock (1998) have
recently shown that the subjective duration of a gap is extremely dependent
on the frequency characteristics of the preceding and following stimuli.
Thus, in the words of Formby and Sherlock, “detection thresholds for
a silent temporal gap may increase by an order of magnitude depending
upon the number, temporal position, and frequency relations of the components
that mark the temporal onset and offset of the gap signal.”
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