Originally Posted by tdv
Mine made similar noise - I figured it was engine noise reflected up from the aftermarket bash plate. I put some sound deadening material (self adhesive) on the inside of the plate, it quieted down significantly.
I also put some rubber grommets between the bash plate and the places where it connects to the frame.
You could try riding with the bash plate removed, see if the noise changes or disappears before trying the padding stuff.
I'm running a TT skid plate. I never thought about it resonating; thank you very much for the input. I'll pull it and see what happens. Thanks again for your help.