I am responsible for investigating excessive noise problems in the cabin of an aluminum fireboat. I have no idea if the problems are with structure borne noise or airborne noise, so here is what I was thinking about doing, please let me know if there are any problems with this method. I was going to bring my laptop onto the boat and record the noise in the cabin over the range of RPM’s of the engine using a program like Audacity. I would then use the built in FFT to determine what frequencies these noises are occurring at. I would then repeat the same procedure by recording the noise at the engine, and determine the frequencies there. If the two spectra were not comparable I would know that the noise was a structure borne problem. Alternatively I guess I could go around looking for vibrations to determine if it is structure borne, however knowing the exact frequency of the problem would be good in order to design a solution. One question I have is when recording the noise, in order to get telling results, what quality of microphone would I need? Would the built in mic on my laptop work okay, or would I need a more advanced mic?