Evaluation of Lateral Attenuation for Aircraft Takeoff-roll Noise by Multi-point Measurement

It is indispensable to consider lateral attenuation for aircraft noise prediction around airport. In 2000's, we proposed lateral attenuation equation "1751M" (modification of SAE AIR1751) available under various meteorological conditions. Afterwards, a lot of new types of aircraft or engines have been introduced, and comparing noise predictions with measurements suggests that "1751M" gives a bit underestimation. Thus, we have started the study to check the validity of lateral attenuation equations for new types of aircraft. At first, the examination on the validity of lateral attenuation equations using long-term noise monitoring at Narita airport had been carried out, but long-term measurement points was not a lot. Therefore, we had planned a multi-point and short-term measurement for the detailed investigation. The multi-point noise measurement were carried out continuously 7 days in each 4 season at Narita airport. In the measurement, aircraft noise was observed at different lateral distances of 190 m - 1460 m. 1/3 octave band analysis results of every moment was recorded at each point. Additionally, for estimation of aircraft position, recording for cross correlation method was carried out at nearest point. This paper introduces an result of over-ground attenuation, which is part of the lateral attenuation.