Audible pedestrian traffic signals: Part 3. Detectability.

This project (10) evaluated audible pedestrian traffic signals (APTS) from three perspectives: 1) the patterns of use and the impact of these signals on pedestrian travel; 2) the physical characteristics of the sound emitted by the Nagoya/Traconex APTS; and, 3) the detectability of the sounds emitted by this brand of APTS. This paper, the last of three companion articles (13,14), describes the detectability of the sounds emitted by the Nagoya/Traconex audible traffic signal, the unit most commonly found in the western United States and almost exclusively in California. To determine detectability, three groups of subjects with normal hearing--young sighted adults (controls), elderly sighted adults, and elderly blind adults--participated in an audiological study. Auditory stimuli, which consisted of APTS sounds embedded in various levels of interfering traffic noise, were presented to subjects seated inside a double-walled sound-treated chamber. The subjects were instructed to press down on a response button as soon as they heard the audible pedestrian traffic signal. The percentage of correct detections determined the absolute detectability of APTS under various S/N ratios. The subjects' speed of response indicated how quickly a pedestrian might begin to cross the intersection upon hearing the APTS.