Acoustic characteristics for effective ambulance sirens

Abstract

Ambulances involved in collisions with motorists at intersections result in a number of negative outcomes including the inability to respond to the assigned emergency task, injury of people, and sometimes the loss of an operational appliance. The warning siren is perhaps the only non-visible device to alerting motorists approaching intersections of a converging ambulance. Acoustic measurements were conducted on several commercial-off-the-shelf sirens, a motor vehicle, and an ambulance, to characterise the noise transmission system. Tests were conducted in order to provide recommendations to improve the audibility and effectiveness of the warning signal. It is recommended that ambulance operators install sirens that broadcast sideways to the ambulance; that broadcast low frequencies so that the siren sound can penetrate into vehicle cabins; and that have signals with short repetition periods to convey high perceived-urgency.