Effects of site geometry on noise control investigated by a scalemodel experiment

Abstract

The geometrical parameters of a building and building groups were simulated in a scale-model study in which a miniature air-jet source moving along a channel in a semianechoic room was used. The scale factor was 20:1 and the frequency range was chosen between 1.2–20 kHz, corresponding to 63–1000 Hz of a traffic noise spectra. The noise generated by the source pass-bys was recorded at 2.8-s intervals and analyzed with the aid of computer programs to obtain time/level distributions in various points in the site model, and to determine the overall and spectrum levels of the line source, by also taking into account the typical spectrums for light and heavy vehicles, air absorption, and microphone directivity. After the validity tests of the technique, the effect of multiple reflections from buildings of different heights, variation of gap size between blocks, and dimensions of barrier buildings and their location angles were studied. The correlations and regressions between the physical dimensions and the noise levels were demonstrated. The results were confirmed by the earlier results of some theoretical and experimental investigations. The further evaluations yielded some simple but useful relationships to estimate the noise propagation in urban environments, for the designer's use especially in noise mapping, which requires a large number of noise data. [The scale-model study was carried out at Purdue University, R. W. Herrick Laboratories, with the consultation of Dr. M. Crocker (1981-82).]