The gas generators such as the MAX series. I have used those personally and they are great. Virtually no noise. The Me series looks great as well. I have not used those personally, but the videos and info make it appear that those are a continuation of their great
track record. I am not certain, but I would assume that the gas is behind the low noise. There's definitely no hiss from the machine. Sometimes with a tank connection that isn't great you get a hiss, but that can easily be rectified with the proper size wrench and occasionally Teflon tape. I am looking at their Atmosphere
Hazer now, and from about 4 feet away there is no audible noise from the machine itself, there is the faintest of fan noise from the small computer style
fan in front that is attached, but nothing that would ever be heard from the audience. The MDG Foggers don't have that small fan, but as I remember their was slightly more noise from the more intense propulsion of the
fog out of the generator, due to the additional pressure introduced by the higher PSI (40 PSI vs 20 PSI) gas. But they had no fan, so I would say it was perhaps a
wash. Still, neither machine could be described as noisy.
In one space, a
Rosco Delta 3000 was used in a particular location (onstage) for a show. The machine could be clearly heard at full from my Tech position mid
house (maybe 60 ft away), even over some moderately loud music. I didn't get any complaints from the director or others, but it could definitely be heard. Same space different show, we got a MAX 3000, and from the same location, it could not be heard even slightly from in the
house. Even during alarm testing while the space was virtually "silent", it could not be heard over lighting
instrument fans and other general background noise in the space. The
fog just appeared. Can't recommend the MDG units enough. Don't let the CO2 dissuade you, it is easier than you think to source and use, and the results are noticeably better than machines without. Their US distributor ACT is great to work with as well.