Dynamo hum?
Fluid trainers offer some noise damping over mag trainers, but tire and bearing noise is still about equal IMO. Fan trainers create more decibels than either, but my Kreitlers will drown out all of the above. Tire noise is going to be about equal with the wind/mag/fluid trainers and bearing noise and resistance source causing the remaining noise source...as amplified or muted by the housing and frame assemblies.
Frankly, I think they are all noisy, some just a bit louder or less loud than others.
A decent rubber mat under the trainer helps attenuate some of the noise. Since indoor training generates body heat and there's no breeze to cool you down, either I stick the rollers down in the cool basement, out in the cool garage where noise is not an issue and I have the stereo or radio blasting anyways (or headphones, sometimes). Indoors, in a room in the house, I always ran a fan to cool me off a bit...adding more noise!