Equivalent noise source strength for a ship

[fer72]

A shipyard has asked us for measure underwater radiad noise from the hull of a vessel, and they are also asking us to convert the pressure levels obtained to an equivalent noise source strength. Does anyone knows how to calculate the noise source strength of a vessel from the radiated noise referenced at 1 meter? Wich is right model dipole or monopole...?
Thanks for your anwers.

 

[GregLocock]

I don't understand "from the radiated noise referenced at 1 meter"

I suspect you need to turn your far field sound pressure measurements into intensity estimates, multiply by the area of each patch, to give a power flux normal to the surface, and then turn that into a power spectrum. I have forgotten the grisly details, any undergraduate acoustics text will have the equations.

Your industry may have a standard approach, the automotive industry certainly does, look for SAE standards on sound power measurement, in particular the hemisphere technique. There is a very similar DIN procedure for estimating the sound power from appliances.

Note that you will have to make some interesting decisions about coherence.


Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.