(b) Two alternative approaches are avail-
Room and the office. The first approach is evalu-
able for estimating the noise reduction from the
ated first. Figure 420 shows the steps involved in
Engine Room to the office. The first approach (the
estimating the SPLs in the corridor space (item 9)
more complicated one) is to consider that the corri-
between the Engine Room and the office. This data
dor first receives the noise from the Engine Room
form is used because the Engine Room wall already
and then transmits it to the office. The second ap-
has been selected to be 10-in. -thick hollow-core
preach (simpler but less accurate) merely treats
concrete block.
the corridor as a double wall separating the Engine
428
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