"
I watched a demonstration of an abrasive waterjet system cutting 1/8"
aluminum and the pump made some noise, but the cutting was under water and
did not make noise that I remember. The whole workpiece was under a few
inches of water that got pumped in before the cutting started and pumped
out to below the workpiece when done.

BobH

the unit's demonstrated at Westech are cutting about 1 inch AL, not too
noisy, the jet is about 1/4 inch above the AL - I don't think I'd want my
ear next to the jet, but it's certainly quieter than a lot of other cutting
tools