EVALUATION OF AIRCRAFT NOISE - EFFECTS OF NUMBER OF FLYOVERS

The subjective impression of aircraft noises when they overlapped vari ous noises was investigated. Instantaneous noisiness was judged using the 'method of continuous judgment by category' developed by the prese nt authors and compared with overall noisiness and physical values. Th e results were: (1) If other conditions are equal, the number of flyov ers can be expressed by adding 10 log N to LAeq,30min, where N is the number of events and LAeq,30min is the equivalent continuous A-weighte d sound pressure level. (2) The increase in noisiness produced by the overlap of aircraft noise depends on the level of background noise. An increase in The level of background noise by about 8 dB decreases the noisiness of aircraft noise by one category. (3) Overall noisiness de pends on the total energy of environmental noise. From a statistical p oint of view, an increase by 1 dB can be significant in the category s cale.