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There's more to this than just painting the machine -- one of the primary concerns of hospitals (and thus medical device makers) is whether the equipment is easy to clean. So just slapping some paint on there isn't enough -- the design has to be embedded into the plastic (which commonly has silver ions in it to help kill germs), or as a single plastic decal that has similar properties.

To reduce the noise, I wonder why they haven't investigated active noise cancelling like the engine mounts used by some auto makers. The computer introduces waveforms that are the inverse of the frequencies they want to reduce. Or at least added mass to panels that conduct noise, using material like Dynamat eXtreme (common in car audio).

The environment around the machine is a pretty hostile one to most technology.

I do think that active noise cancellation is a brilliant tool for solving many repetitive noise issues ( I explored its use in a server room, dual purpose was, if anything was 'wrong', I could hear the room get louder as the fans lost sync with the inverse waveform. )

However given the sensitive nature of the machines, I wonder if there would be any issues caused by projecting loud inverse waves into the room the machines operate, since it would be very strange if these equipment manufacturers didn't explore the active noise cancellation technology as a way to mitigate the ear splittingly loud noise they produce.

The car makers use two kinds of active noise reduction. One is the injection of inverse waves into the car's stereo, to reduce road noise and body panel vibration. This is controlled by a microphone in the cabin (probably the same one used for hands-free phone calls).

The other one is in the engine mounts, where they have a liquid inside the rubber mount that can stiffen up on command (maybe magnetorheological[1], maybe some other kind), and this is used to counteract the vibrations the engine would transmit to the body/chassis. This is controlled by the ECU because it knows when the engine is on a power stroke and can thus apply correction on a timing basis.

I would think the latter would be what the MRI makers would want to investigate -- they've got a huge spinning mass[2] with components that vibrate. Much like an engine. :)

[1] http://en.wikipedia.org/wiki/Magnetorheological_damper

[2] At work, so can't post a video link, but if you look for "cover off mri" it's really scary/impressive how they work.

The machine from the story is using a decal.

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