The pulse tubes are really loud. We've wrapped the helium lines in sound absorbing foam, and we have a cage around the top of the cryostat also lined with foam, but it's still pretty loud.
To make this an interesting physics question I ask: how is the sound getting from the mechanism to my ears? Does the sound travel through the support frame? Through the helium lines?
Given the transduction channel, is there an effective way to reduce the noise?