The IMA system does seem to emit a sort of high-pitch whine that some people have heard, others don't. It changed tone depending on whether it was charging or assisting. I never did hear it until fairly recently, but hear it occasinally now.

It's most audible at lower speed or even stopped (while the engine is not in autostop) with the radio and fan down or off. I don't know if the noise cancellation system is a little out of kilter, or not designed to handle that high frequency.

Could your noise also be wind around a gasket? Or do you also hear it while stopped?