Preaspiration in the Nordic Languages: Synchronic and Diachronic ...
Preaspiration in the Nordic Languages: Synchronic and Diachronic ...
Preaspiration in the Nordic Languages: Synchronic and Diachronic ...
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are better discrim<strong>in</strong>ated than are adapted responses (i.e., with low neural<br />
discharge rates). In one experiment, Lacerda <strong>in</strong>vestigated <strong>the</strong> difference<br />
<strong>in</strong> discrim<strong>in</strong>ability between short, syn<strong>the</strong>tic vowel stimuli with abrupt vs.<br />
gradual onsets. F2-values for <strong>the</strong> stimuli varied, rang<strong>in</strong>g from 1510 Hz to<br />
1690 Hz <strong>in</strong> 30-Hz <strong>in</strong>crements. F1 was fixed at 200 Hz, F3 at 2600 Hz,<br />
<strong>and</strong> F4 at 3600 Hz. A two-alternative forced choice paradigm was used<br />
<strong>and</strong> subjects were asked to note whe<strong>the</strong>r or not <strong>the</strong> two alternatives presented<br />
were different. Lacerda found that when <strong>the</strong> F2 difference between<br />
two stimuli was 60–90 Hz, <strong>the</strong> stimuli with abrupt onsets had significantly<br />
better discrim<strong>in</strong>ation rates than did gradual stimuli. This <strong>in</strong>dicates<br />
that <strong>the</strong> F2 differences have more auditory salience <strong>in</strong> abrupt than<br />
<strong>in</strong> gradual stimuli.<br />
However, <strong>in</strong> an identical experiment us<strong>in</strong>g aperiodic <strong>in</strong>stead of periodic<br />
stimuli (thus essentially syn<strong>the</strong>sis<strong>in</strong>g an aspiration, but possibly us<strong>in</strong>g<br />
a more fricative than aspirative source), Lacerda did not f<strong>in</strong>d that<br />
gradualness of onset lessened discrim<strong>in</strong>ability at all. Instead, discrim<strong>in</strong>ability<br />
scores for stimuli with abrupt <strong>and</strong> gradual onsets were almost<br />
identical. The scores lay somewhat below those for abrupt periodic stimuli,<br />
but above those for gradual periodic stimuli. (This applies to <strong>the</strong><br />
cases <strong>in</strong> which F2 differs by 60 Hz or 90 Hz; o<strong>the</strong>r differences are much<br />
smaller). Thus <strong>the</strong> abrupt vs. gradual difference found <strong>in</strong> <strong>the</strong> first experiment<br />
does not appear <strong>in</strong> <strong>the</strong> second.<br />
One may note that aperiodic sounds with abrupt <strong>and</strong> gradual onset<br />
are both “natural” <strong>in</strong> speech (abrupt onset = affricate, gradual onset =<br />
fricative). Periodic sounds with an abrupt onset (vowels) are also “natural”<br />
<strong>in</strong> speech. However, periodic sounds with a gradual onset (such as<br />
<strong>the</strong> one syn<strong>the</strong>tically created by Lacerda) are not. Perhaps subjects are<br />
better able to discrim<strong>in</strong>ate sound patterns that are used consistently <strong>in</strong><br />
speech than sound patterns that humans may not even be able to produce<br />
(such as <strong>the</strong> periodic gradual onset vowel stimulus used <strong>in</strong> Lacerda’s<br />
experiment).<br />
Review<strong>in</strong>g <strong>the</strong>se facts, one may perhaps conclude that <strong>the</strong>re is some<br />
degree of correlation between discharge rate <strong>and</strong> auditory salience, but<br />
that <strong>the</strong> two can <strong>in</strong> no way be equated directly. Thus a three-fold <strong>in</strong>crease<br />
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