This section explains how to perform noise measurements at sea and also outlines the concepts.
Description
When the vessel is stopped and no other acoustic equipment is active, the noise estimate should be approximately —145 dB or
lower
If the noise is substantial and mainly caused by the propeller, the procedure should be repeated with idfferent combinations
of pitch and propeller speed if possible to determine the most favourable settings.
If the noise estimate increases significantly when switching to Active mode it is likely due to the acoustic backscatter from objects in the water.
The influence from the other acoustic instruments can be evaluated by measuring the noise with and without these other acoustic
instruments turned on and comparing results. In this case the instruments must be synchronized and the procedure shall be
modified to allow external synchronization.