Abstract
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).
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