The only moving part on my converter is the fan .. might take a peak and see if there is something blocking blades maybe blow some compressed air. If that doesn't fix it then take the rig back and ask them to replace the converter.
smkettner wrote: A 2015? Sounds like a warranty issue. What brand?
X2, your profile says 2015 for the FW. If so get them to fix it, as it is likely something loose/vibrating and might need replacement to correct. My converter doesn't make sound except the fan when under moderate to heavy load.
It may be the laminations in the transformer vibrating. If so then tightening the screws that go through it (if present) may help. But, sometimes the only thing you can do is replace it. Look for anything else in there that might be vibrating though.