DG 1110-3-106
A Correct Location for Secure Area
B W r o n g Location for Secure Area
Figure 5-9
Locating Intense Noise Sources.
64 db at 1,280 ft.
b. Remote Location.
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Dissipation of loud sound requires considerable
distance. The intensity of sound energy is inversely
34 db at 40,000 ft. (7 1/2 miles)
proportional to the square of the distance from the
etc.
source. In other words, doubling the distance from a
sound source reduces the level of sound energy
Since 35 decibels is them aximum desired background
received by a factor of four, which is equivalent to a
noise level for classrooms and study areas, it is clear
that distance alone is not a practical sound barrier
reduction of 6 decibels for each doubling of the
distance between source and receiver. The operation of
between the classroom environment and related
heavy armored or transportation equipment produces
training on loud equipment. Even single glazed
between 80 and 120 decibels of sound at a distance of
windows in a typical building will reduce sound
transmission from outside the building by
20 feet. Aircraft may produce in excess of 140
approximately 30 decibels. Therefore with typical
decibels. Assuming 100 decibels at 20 feet, the sound
school construction disturbing noise sources need to be
diminishes as follows:
100 db at 20 ft.
kept at a distance only great enough to reduce the
ambient noise level around school buildings to a level
94 db at 40 ft.
of 65 decibels. Normal construction will filter this level
88 db at 80 ft.
82 db at 160 ft.
of sound to acceptable classroom levels. In large
76 db at 320 ft.
schools, it may be possible to reduce noise levels by
designing to take advantage of interposing terrain
70 db at 640 ft.
features.
5-8
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