On the power and frequency of auditory signals on emergency vehicles

Sirens from emergency vehicles are particularly annoying for people living in the vicinities of hospitals. The power regulations for sirens vary for different countries as well as it does their frequency content. In order to reduce their annoyance the present work computes the optimal output power and frequencies of the siren by taking into account the car's sound insulation, the background noise inside the car and the masked threshold of hearing. The combination of these parameters gives rise to frequency windows where the sirens are more effective, so new tones are proposed and their annoyance is assessed through a jury test procedure.