17 Underwater Noise Study Toward Propeller Rotation
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Fig. 17.9 Rpm of motor vs depth of the measuring device at 100 mm horizontal position of
measuring device and 0 mm vertical center position of measuring device with 44 mm 3 blade
propeller size
noise level where at 120 mm depth, it shows the lowest noise level compared to
30 mm, 60 mm, and 90 mm.
Based on Fig. 17.12, high revolutions per minute show the higher noise level
and as mentioned in Fig. 17.11, more cavitation is created with higher speed of the
propeller rotation thus will generate high noise level. As mentioned in Fig. 17.7, the
larger the size of the propeller, the higher the noise level together with the higher
the number of blades, the higher the noise level. This is because a high number of
propellers and a larger size of the propeller create more cavitation. The noise level
at size number 4 shows that it decreases because at size number 3, it is two-blade
propeller with 48 mm in diameter while at size number 4, it is a three-blade propeller
with 40 mm in diameter