Some component in my computer emits an annoying high pitched sound, like a constant screetching. I'd really like to dampen the sound while providing enough air flow for the computer. The computer is wedged between my desk and the side of a drawer cabinet, so I can suspend some material there. But everything I tried so far didn't noticably reduce the sound.
I tried blister foil, several sheets of corrogated cardboard and a piece of foam that was unfortunately too small. I even read some scientific studies about high frequency sound insulation, but they are written from an industrial point of view and suggest thick MDF boards as the best insulator.
Before I buy bulky packs of materials that may not work after all, I'd like to ask: Which material that a hobby crafter might have at hand acts well as an acoustic insulator for high frequencies?
P.S.: Of course replacing the problematic component would fix the noise problem, but let's assume that's impossible (at least short term) for the sake of the question.