The treadmill motor should work for a prototype but what you should be looking for is probably a lot different than what you are looking for. It is very possible to build a quiet, low volume, high pressure air compessor. Generally smaller compressors make a lot of noise from two places. The intake and the non-lubricated drive system. For low volume applications you may be able to get away from a piston compressor and go to a diaphragm
Setup. A small 120 motor would have no issues and it would really reduce the price
Setup. A small 120 motor would have no issues and it would really reduce the price