Test: Air & Sound Pollution - 2 - Civil Engineering (CE) MCQ

Photochemical reactions form O₃, PAN, formaldehyde, etc.

Reverberation time is the time required to reduce the intensity to one-millionth of its initial value.
Sound level (dB) 

TTS (Temporary Threshold Shift) is temporary impairment of hearing acuity as indicated by change in the threshold of audibility PTS (Permanent Threshold Shift) is related to permanent hearing loss. The sound foci are formed when sound waves are reflected from concave surface.

Wind Speed u = 4 m/s
Stack gas speed V_s = 8 m/s
Diameter d = 1 m
Heat rise Q_h = 2000 kJ/s
We know that effective height of stack,

For excellent acoustic conditions, reverberation time should be between 0.5 to 1.5 seconds.

CO₂ is major green house gas and absorbs long wave radiations like infrared radiation.

Sound absorbing materials reflect the noise and they are mostly used in theatres etc.

Photochemically, the NO_x and hydrocarbons are two groups of chemical compounds which are the necessary ingredients for the production of photochemical smog.

The end product of photochemical reactions is photo chemical smog consisting of air contaminants such as O₃, PAN, aldehydes, ketones, alkyl nitrates and carbon monoxide.