We considered a method for calculating the sound exposure level (L_AE) of helicopter noise. It was assumed that helicopters have no directivity and that the propagation of sound can be expressed in a simple function of distance from an observation point to a sound source. We derived a formula for L_AE by integrating the sound energy along a finite or an infinite flight segment. And we classified the value of power level into three groups by the maximum takeoff weight. The values calculated from the formula agree with the results of test flights in which three types of helicopters each took three moving operations of approach, takeoff and level flyover.

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The questionnaire was carried out to get the basic data in order to create an amenity of sound environment in Matsudo city, and was conducted aiming at families with junior high school students in the city. We asked about what the citizen think about Bell sound as a soundmark by writing freely about “How do you think about Bell sound?” in the questionnaire. The analytical results of the citizen's awareness for Bell sound were classified into seven groups according to the word coupling pattern.
The group having the reminiscence of Bell sound and the group having the experience of hearing Bell sound are the two biggest, followed by the group having the action of striking a bell and the group having the desire of hearing Bell sound and striking a bell. Bell sound is identified as the sound to announce time and the sound of new year's eve bells in the citizen's environment recognition from this survey.
We obtained the basic data for improving the noisy sound environment in the urban area.

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