Road Traffic Noise Attenuation by Vegetation Belts at Some Sites in the Tarai Region of India

Noise measurements have been carried out at eleven different sites located in three prominent cities of the Tarai region of India to evaluate the effectiveness of vegetation belts in reducing traffic noise along the roadsides. Attenuation per doubling of distance has been computed for each site and excess attenuation at different 1/3 octave frequencies has been estimated. The average excess attenuation is found to be approximately 15 dB over the low frequencies (200 Hz to 500 Hz) and between 15 dB to 20 dB over the high frequencies (8 kHz to 12.5 kHz). Over the critical middle frequencies (1-4 kHz), the average excess attenuation (between 10-15 dB) though not as high, is still significant, with a number of sites showing an excess attenuation of 15 dB or more at 1 kHz. The results indicate that sufficiently dense vegetation belts along the roadsides may prove as effective noise barriers and significant attenuation may be achieved over the critical middle frequencies (1-4 kHz).