In Japan, the electronic ambulance siren was introduced in 1970 in order to reduce the effect of noise on residents. The new regulation about electronic siren asks that the sound pressure level of siren must be between 90dBA and 120dBA at the 20mpoint in front of an ambulance. In 1991, the total number of ambulance calls in Japan were over 2.8 millions and it increases 77 thousands every year. Due to this increment, the ambulance noise becomes more serious problem year by year. Especially innight time, the residents who are living along the major street often argue its sound in term of "uncomfortableness" or "difficulty to sleep" [1] [2]. On the other hand, it is often pointed out that the siren is not always effective to let the generaldrivers detect a approaching ambulance [1] [3]. While leaving aside the visual aspect of the ambulance's alarm system, there seems to be two main reasons of ineffectiveness as sound alarm; one is that most drivers use audio equipment with all windowsclosed, and the other is that they also quite concentrate ill operating their vehicles.In this paper, an ambulance siren is evaluated from both aspects of residents and drivers. The questionnaires about ambulance siren are conducted for the residents of Kurume city area and 1183 effective answers are analyzed. To investigate the drivers'side phenomenon, the experimental measurements are performed. At first, the sound environment inside the automobile is measured. Then the dependency of thresholds of ambulance siren is measured both on music reproduction level and speed of vehicle.
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