Temporal resolution is an important area of hearing science research. It is the ability to perceive or discriminate sound segments spaced closely in time as separate events, and is an essential component of speech processing. The gradual degradation of temporal resolution that occurs within the normal aging population may contribute significantly to the speech perception difficulties commonly experienced by aging individuals. Psychoacousticians have identified masking overshoot, a psychophysical phenomenon, as one measure of temporal resolution. Overshoot refers to improved detectability of a short-duration signal as the onset of that signal is delayed relative to the onset of a longer-duration masker. For example, a signal that occurs 20 milliseconds after the onset of a masker is easier to detect than a signal that occurs 1 millisecond after the masker onset.
Previous research into the investigation of the overshoot effect has been performed by several students at Western University. Wong's (2001) research investigated the role of aging on the presence of overshoot in older versus younger normal hearing individuals. Lui's (2002) research examined the time course of the overshoot function using six different signal onset delay times of 1, 5, 10, 20, 50 and 250 ms relative to the onset masker. However, in contrast to Wong's (2001) study, participants were exclusively younger normal hearing listeners between the ages of 19 and 24 years old. Lastly, Hoffman's (2003) research investigated the relationship between overshoot and gap detection in younger and older normal hearing individuals. This most recent study did include some exploratory data that was collected from a subset of the subject pool where four overshoot signal onset delay masked thresholds (5, 10, 20, and 50 ms) were obtained in addition to the two onset delays used in the original procedure (1 ms and 250 ms). In total, six mean masked signal thresholds were calculated for this subset. However, results from statistical analysis were only reported and discussed for the data collected at 1 and 250 ms trials for all participants. As such, the present study will be a compilation and extension of these past research designs discussed above. More specifically, this study will investigate the differences in the threshold and time course characteristics of the overshoot effect in younger versus older normal hearing adults.