In some environments, there is a serious mismatch between the perceived (psychoacoustic) urgency of a warning and its situational urgency. In addition, many auditory warnings are not detectable within their environments. This research examined several prominent pulse parameters which affect the perceived urgency and detection time of auditory warning signals. These elements included pulse format (multitone sequential, multitone simultaneous, and rising sawtooth frequency-modulated pulse formats), pulse level (65 dBC and 79 dBC), and time between pulses (0 ms, 150 ms, and 300 ms). The environments of interest were those settings with steady-state broadband machinery noise. Conditions included a loading task which presented additional attentional demands upon the subject during the signal detection task. Free-modulus magnitude estimation quantified the relationship between auditory signal parameters and changes in perceived urgency. The method of paired comparisons was used to compare the perceived urgency of the auditory stimuli. Simple reaction time measured signal detectability. Signal effects were analyzed using a multivariate approach.

Results indicated that there was a small but statistically significant relationship between perceived urgency and detection time. As perceived urgency increased, detection time decreased. Both perceived urgency and detection time were influenced by pulse level and format. The higher pulse level resulted in a greater perceived urgency of the signal and shorter detection time. Sequential signals were rated as less urgent than the other pulse formats, and subjects took longer to detect their occurrence. Under most conditions, there was no significant difference in the perceived urgency or detection time of simultaneous and frequency-modulated pulses. Time between pulses (inter-pulse interval) affected only perceived urgency, not detection time. The shorter the time between pulses, the greater the perceived urgency of the signal.