Decreasing speed
This procedure describes how to decrease speed in order to do noise measurements at sea.
Context
Procedure
1 Start with maximum vessel speed.
2 Disengage the propeller as quickly as possible to allow the vessel to slow down by itself.
3 For every 1 to 2 knots speed reduction, read the Noise estimate from the Extras menu and make a note of the value..
If the noise decreases quickly towards the same level as at 0 knots when the propeller has been disengaged, this means that the propeller is a main source of noise. If the noise at decreasing vessel speed is more or less equal to the noise level at increasing speed, the noise is probably flow-noise, or caused by electrical cables, motors or instruments. Usually the noise is a combination of these sources.