quote="Rusty075"]All sound absorbing materials dissipate the sound in the form of heat.
Its the First Law of Thermodynamics in action.
The energy has to go somewhere.
But Dynamat is dissipating sound that would otherwise resonate the case wall (or other piece of sheet metal) and then re-radiate as noise.
The foam (or ceiling tile) absorbs sound waves directly (by providing air friction). It only works for high pitched sounds because of the way the sound waves convert from pressure to motion depending on how far they are from a reflective surface - the conversion is dependent on the length of the wavelength - and the foam/tile isn't very thick so it isn't going to catch much low frequency energy as motion.
I'm afraid I'm not explaining this well (need a white-board) - have a look at F. Alton Everest's books for a good explanation with diagrams.
Anyway, I *have* had good luck attenuating high pitched disk noise by linking a case with automotive sound-deadening *foam* - but it was at least 3/4" thick. I'm not sure PaxMate (which is more like 1/4" thick) is going to attenuate noise low enough frequency to *hear*. Might make your dog happier, though...