The Perceived Urgency and Detection Time of Multi-Tone and Frequency-Modulated Warning Signals

The perceived urgency and detectability of auditory warning signals are important safety considerations. When designed correctly, auditory warning signals can improve performance and reduce accidents. However 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 (sequential, simultaneous, and sawtooth frequency-modulated pulses), 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. A loading task presented additional attentional demands during the signal detection task. Free-modulus magnitude estimation and the method of paired comparisons quantified perceived urgency. Simple reaction time measured signal detectability and signal effects were analyzed using a multivariate approach.

Results indicated that detection time decreased as perceived urgency increased. The higher the pulse level, the greater the perceived urgency of the signal and shorter the 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.