Method of predicting road traffic noise around small-scale roundabouts in Japan

Abstract

This study was conducted to elucidate the actual situation of noise levels around roundabouts in Japan and to develop an energy-based prediction method to calculate equivalent noise levels around roundabouts. Two roundabouts in Fukuoka Prefecture in Japan were surveyed to clarify the noise levels around them. The correspondence between calculated and measured noise levels would be better if the sound power levels of Common Noise Assessment Methods in Europe (CNOSSOS-EU) were applied with further reduction of about 3 dB. In small roundabouts typically introduced in Japan, vehicles pass slowly at an almost constant speed. Therefore, setting the sound power level while assuming the steady running of vehicles at low speeds is appropriate. Measurement survey results clarified that a vehicle speed about 20 km/h on circulatory roadways is appropriate and also clarified that the formula for steady running can be used by applying the sound power level used for ASJ RTN-Model 2018. We propose a method of predicting equivalent noise levels by calculating single-event noise exposure levels from unit patterns according to the ASJ RTN-Model 2018 prediction procedure. The calculation and measurement results at 25 points around two roundabouts show good agreement. The findings confirmed that this proposed calculation method can accurately predict equivalent noise levels around roundabouts.