The noise -reduction coefficient (NRC) of a material is evaluated between the frequency range of 250 Hz and 2 kHz because
A) it is virtually impossible to evaluate this property outside the above frequency range.
B) the human ear is insensitive to noise outside the above frequency range.
C) most of the sound energy in human speech lies in the given frequency range.
D) most of the sound energy in the noise produced in buildings lies in the given frequency range.
E) none of the above.
C) most of the sound energy in human speech lies in the given frequency range.
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Identify the statement that is false.
A. The population of the 13 colonies, mainly Anglo-Saxon, was the least mixed to be found anywhere in the world. B. The South, holding about 90 percent of the slaves, displayed its historic black-and-white racial composition. C. New England, mostly staked out by the original Puritan migrants, showed the least ethnic diversity. D. The Middle Colonies received the bulk of later white immigrants and boasted the most variety of peoples. E. In 1775, outside of New England, about one-half the population was non-English.
Find i? in the circuit of Fig. 10.54.
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Where can an HVAC system's smoke control mode be controlled from?
A. The lobby of the building B. A mechanical equipment room C. Control stations in main building corridors D. A firefighter's smoke control station (FSCS)
?Electrode classifications are prefixed with the letter ____.
A. ?E B. ?F C. ?K D. ?L