Ba. Schneider et al., GAP DETECTION AND THE PRECEDENCE EFFECT IN YOUNG AND OLD ADULTS, The Journal of the Acoustical Society of America, 95(2), 1994, pp. 980-991
Thresholds for detecting a gap between two Gaussian-enveloped (standar
d deviation=0.5 ms), 2-kHz tones were determined in young and old list
eners. The gap-detection thresholds of old adults were more variable a
nd about twice as large as those obtained from young adults. Moreover,
gap-detection thresholds were not correlated with audiometric thresho
lds in either group. Estimates of the width of the temporal window of
young subjects, based on the detection of a gap between two tone pips,
were smaller than those typically obtained when a relatively long dur
ation pure tone is interrupted [Moore et al., J. Acoust. Sec. Am. 85,
1266-1275 (1989)]. Because the amount of time it takes to recover from
an adapting stimulus is likely to affect gap detection thresholds [Gl
asberg et al., J. Acoust. Sec. Am. 81, 1546-1556 (1987)], smaller esti
mates of temporal window size would be expected in this paradigm if th
e amount of adaptation produced by the first tone pip was negligible.
The larger gap-detection thresholds of old subjects indicate that they
may have larger temporal windows than young subjects. The lack of cor
relation between audiometric and gap-detection thresholds indicates th
at this loss of temporal acuity is not related to the degree of sensor
ineural hearing loss. In a second experiment on the precedence effect
using the same subjects, a Gaussian-enveloped tone was presented over
earphones to the left ear followed by the same tone pip presented to t
he right ear. To more realistically approximate a sound field situatio
n, the tone pip presented to each ear was followed 0.6 ms later by an
attenuated version presented to the contralateral ear. The delay betwe
en the left- and right-ear tone-pips was varied and the transition poi
nt between hearing a single tone on the left, and hearing two such sou
nds in close succession (one coming from the left and the other from t
he right) was determined. The transition point in this experiment did
not differ between young and old subjects nor were these transition po
ints correlated with gap-detection thresholds. These results indicate
that monaural temporal acuity and binaural echo suppression may be bas
ed on different processes.