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Variable-Duration Notched-Noise Experiments in a Noise Context James J. Hant, Brian P. Slropc. Abeer A. Alwan

Summary: Variable-Duration Notched-Noise Experiments in a Noise Context
James J. Hant, Brian P. Slropc. Abeer A. Alwan
Speec[) Proces~irlg atl(f Ali(litoq Perceptiott Labor(ttoq. Departolcilt ofElectric(~[ Et~gitlcetitzg, Scflool of
Ei~gitleeriilg att(l Applied Scietlces, UCLLi, $05 Hilgord Atetlile, Los Atlgc[es, Cal forrlia, 90095
Abstract: A variable-duration notched-noise experiment was conducted in a noise context, Broadband noise preceded and fol-
lowed a t(mc and notched noise of similar duration, Thresholds were measured at four dura[iorts ( 10, 30, 100, and 3M ins), lwo
ccntcr frequencies (0.6, 2,0 kHz), and five relative nutch-wid[hs (0,0, O.1, 0.2, 0.4, 0.8). At 0.6 kHz, IO-ins thresholds decrease 6
dB across notch widths while 300-ms thresholds decrease over 35 dB. These durational [rcrrds are similar but less pronounced at
2 kHz, In a second experiment, the short-duration notched rtoisc was rcplaccd with a flat noise which provided an cquiv~lent
amount of simultaneous masking and thresholds dropped by as much as 20 dB. Thus, :hc clcva[cd thresholds at short dura[ions
are dependent on the spcctml shape of the simultanc(~us masker, which may imply reduced frequency selectivity.
Short-duration speech signals, such as plrssives, are often confused in noisy environments. To model these confusions,
it is necessary to characterize our ability to resolve the spectral components of short-duration stimuli in background
noise. Previous notched-noise masking experiments using a short-duration tone and long-duration no~ch suggcs[ [hat
frequency selectivity develops nearly instantaneously (3), (5). However, other noise-masking studies which usc a
broadband noise-masker suggest decreased frequency selectivity at short-durations (2), (4). To assess the discrepancy
between these studies, a variable-duration notched-noise experiment was conducted in a broadband-noise context.
Figure I shows a schematic spectrogram of the s[irnu]i used in the experiment. Both the no[chcd-noise and the sur-


Source: Alwan, Abeer - Electrical Engineering Department, University of California at Los Angeles


Collections: Computer Technologies and Information Sciences