(3) SPLS in Engine Room No. 1.
(a) Engine Room No. 1 will ultimately have
3 engines and 3 generators. Figure 42 gives the
PWL of one engine, and tables 728 and 729 of the
N&V manual give PWL data for a generator. A
3500-hp engine would drive a generator with a rat-
ing of about 2.4 MW. The generator is direct-
coupled to the engine, and would be driven at 450
rpm. Table 728 of the N&V manual indicates an
overall PWL of about 105 dB for a generator of this
speed and power. The PWL of the engine casing is
123 dB (from fig. 42), so it is clear that the engine
is the controlling source and the generator can be
ignored.
steps used to obtain this SPL.
"
L
L P = LW + REL SPL ,
Column 2 gives the PWL of the engine casing (from
Part A of figure 42), column 3 gives the Room
where REL SPL is negative valued, as shown in
Constant (from fig. 45), and column 4 gives the
column 4 of table 41. The 3-ft. SPL values are
REL SPL (from table 57 of the N&V manual) for
then inserted in Items 1 and 4 of DD Form 2296
the 3-ft. distance and the various R values of col-
(fig. 4-7).
umn 3. Finally, column 5 gives the SPL, as ob-
tained from equation 53 of the N&V manual,
which is
4-9
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