Noise insulation

[Expo]

What do you folks with multiple motor benches use to keep the noise levels down? Dynamat is rather expensive, anyone ever used thin foam sheet insulation? Undercoating?

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I was thinking about this myself a while back, but my latest bench has turned out very quiet without any additional acoustic treatment. My blower is very softly spring mounted to eliminate any coupled vibration into the frame, and the exhaust air all goes down a stormwater drain coming out somewhere ? miles away. All my panels are 1" MDF which is fairly stiff and heavy all by itself.

Getting back on topic. There seem to be two approaches to this. Absorption, using felt, foam rubber, or something similar, or damping the vibrating panels with sheet lead. Or maybe a combination of the two.

I have not tried it, but very thick soft foam rubber glued to sheets of lead would probably be the ultimate do it yourself noise transmission barrier.