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to reduce noise levels. Machine enclosures are provided in machine shops to curb
noise levels (Fig.  7.2). Correctly designed, vegetation barriers can be used to
enhance near-road air quality, either alone or along with solid noise barriers (Baldauf
2017). Tree shrubs around industries would reduce the noise levels at the boundary
of industries.
Road traffic noise is one of the main noise pollution problems worldwide. Even
though the problem has the same magnitude worldwide, developed countries have
adopted the method of providing noise barrier between road and residential area to
curb noise pollution arising from road traffic. Since reflective material like concrete
or brick bounces sound waves, sound absorptive barriers are now used in many
places to reduce overall noise.
Apart from road condition, the noise in vehicle depends on engine speed and
vehicle speed besides how the vehicle is used (Vibha 2019).
1. Engine speed effects:
(i) Intake and exhaust noise
(ii) Fan noise
(iii) Engine noise
2. Vehicle speed effects:
(i) Transmission noise
(ii) Tyre noise
3. Operational factors:
1. Load on vehicle
2. Fuel used
Fig. 7.2 Enclosure for diesel generator
7 Noise Pollution