Noise emitted from a source can be controlled by applying any one or all of the following techniques.
Noise control at source
Reducing of impact / impulse force: Impact noise is created by hammers, crushers hoppers, resulting from impacts of rock and steel. It can be reduced by optimizing the impact distance and covering either or both the impact surfaces by rubber or materials of such type.
Balancing of moving mass: Some noises are created by sudden inrush or discharge of air e.g. leakage of compressed air through pipelines, ventilation fanes, and air compressors. This type of noises is created due to discharge of high volume of air through restricted path. So this noise can be reduced by using “mufflers” which are simple expansion chambers to slow down the velocity of exhausting air. Mufflers can attenuate the noise level by 5-10 db (A).
Vibration isolation: Machine vibration is the source of one of the highest volume of noise. Noise generated by the mechanical vibration of machine or its part can be reduced by damping or isolation of the vibration. Rubber or cork between the moving parts of the machine and the surrounding stationary structure.
Modified manufacturing design: Problem of noise emission can be tackled at the design and manufacturing stage by making suitable adjustments in the design itself. Eg: enclosing the engine parts within proper noise insulating material.
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