A. With greater number of blades
B. Of increased diameter
C. Both A. & B.
D. Neither A. nor B.
Related Mcqs:
- High noise levels produced during operation of fans and compressors can be reduced by using__________________?
A. Mufflers (silencers)
B. Acoustic absorbent
C. Lagging of noisy duct
D. None of these - Aerodynamic noise resulting from turbulent gas flow is the most prevalent source of valve noise in fluid flow control. It is caused due to_________________?
A. Reynold stresses
B. Shear forces
C. Both A. & B.
D. Neither A. nor B. - Major sources of noise in furnace operation arises from air inspirators, combustion, side wall vibrations and fluctuation in the process heat load. A 50% increase in fuel firing rate may increase the furnace noise level by about ____________ decibels?
A. 3
B. 30
C. 7
D. 70 - The major reason of hydrodynamic noise (i.e., noise resulting from liquid flow) is_________________?
A. Pipe vibrations
B. Cavitation
C. Boundary layer separation
D. Fluctuation in liquid flow - Lung cancer & DNA breakage are the major ill effects of excessive ozone exposure to human beings. Ozone layer depletion in the atmosphere is mainly caused by the presence of________________?
A. CO2
B. SO2
C. Hydrocarbons
D. CFC (chloro fluoro carbon) - The resistance of water to the passage of light through it is a measure of the___________________?
A. Turbidity
B. Color
C. Hardness
D. Dissolved gases - The progressive warming up of the earth’s surface is mainly due to the___________________?
A. Automobile exhaust
B. Blanketing effect of CO2 in the atmosphere
C. De-forestation
D. Thickening of ozone layer - Noise pollution level in a chemical plant is expressed in __________________?
A. Roentgen
B. Decibel
C. Hertz
D. None of these - Maximum allowable noise exposure limits for a man working for 8 hours a day in a noisy chemical plant is about ______________ decibels?
A. 20
B. 60
C. 90
D. 120 - Noise emitted by a ventilation fan at a distance of 3 metres is about _____________ decibels?
A. 85
B. 105
C. 125
D. 145
