Figure 5-8. Compound Barriers

Noise and Vibration Control
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57

TM 5-805-4/AFJMAN 32-1090

Part A. Source Radiates From a Hole in the Wall

Part B. Compound Barrier, Constructed

Part C. Compound Barrier, Natural

Figure 5-8. Compound Barriers.

received inside the upper floor of the residence. If

upper windows of the residence (Co1 4 = Co1 2 -

the noise is excessive, what could be achieved by

Co1 3). Column 5 gives the noise reduction for the

moving the cooling tower to the lower roof position

type E wall (from table 5-7), Column 6 gives the

shown in Part E of the figure? Assume the entire

indoor SPL, and Column 7 shows the indoor SPL

PWL radiates from the position near the top of the

values that correspond to an NC-25 curve, sug-

cooling tower.

gested here for sleeping. Comparison of the esti-

mated SPL values with the NC-25 values shows

(1) Location "A". Table 5-8 summarizes the

excess noise of 8 to 12 dB in the 250- to 2000-Hz

data for this part of the analysis. Column 2 of the

bands (Co1 8).

table gives the sound power level of the cooling

tower, Column 3 gives the distance term for the

(2) Location "B". Table 5-9 summarizes the

480-foot distance (from table 5-4) and Column 4

data for this alternate location of the cooling tower

gives the calculated average SPL outside the

where it receives the benefit of the barrier effect of

5-11

Index