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Noise mitigation in built environment

Over the years, we have somehow ignored the detrimental impacts of of the ambient sounds that urbanization has been adding steadily. Several noise  mitigatioin  measures could be considered by designers of the built environment. The understanding of the science of sound travel and behavior could help.

When its comes to mitigation of noise, basic understanding of the science of sound travel will help.

a) Sound travels in the form of waves. It is a form of energy and needs a medium to travel.
b) It travels faster through a denser medium like water than air.
c) The speed of sound travel increases with increase in temperature. However at higher altitudes the speed of sound decreases due to decrease in temperature of air.
d) Concave surfaces and spaces like valley’s gather the sound waves and increase the amplitude, where as convex surface disperse the sound waves and thereby decrease its amplitude.
e) Firm and dense medium transmits the sound faster and in the same magnitude. Porous and lighter media,reduce the speed of sound and also absorb it.

New Developments

Noise mitigation for the built environments starts at planning level. The primary strategies could be as follows:

Orientation and programming: Zones sensitive to loud sounds like Hospitals, schools, residences, etc need to be separated from noise generating activities in planning or oriented away from the source of noise.  In dense urban areas where large buffering is not possible, the habitable spaces can be pushed back by features like balconies, flower beds etc. For habitable spaces facing the source of noise,  windows and openings can be oriented in the direction perpendicular to the sound. This will reduce the decibels substantially, and further reduction can be archived by sound attenuation of windows and walls

Ar. Meenal Sutaria
Ar. Meenal Sutaria

Deflection of sound: For openings facing the source of noise, sound can be prevented from reaching the openings by deflecting  it. Fenestrations  or facade can be designed to achieve this.

This deflected sound can be intercepted by green cover or trees to further decrease the amplification at higher altitudes. Alternatively, the surfaces can be finished with sound absorbing medium that would prevent the deflection, but reduce the amount of noise incident on the habitable room

Sound Attenuation: Higher floor of many  buildings facing the roads have amplified sound reaching them, especially near flyovers. Multi-layered vehicular travel has led alleviation of noise and air pollution at higher floors. In existing buildings this can be checked by providing sound attenuation to the walls or modify the glazing in the windows to Insulated glazing. Additionally externally sound absorbing medium can be used on the bottom of  overhangs to further reduce the reflected or deflected sound. Unless and until, measures are taken to control the level of noise, the ongoing urbanization and industrialization may complicate the problem so much that it becomes incurable.

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