Hi Suesi,

I think you may be misunderstanding what's being meant when noise is mentioned in some threads.?

Most are NOT talking about the DB noise of the machine but the Electrical interference "noise" coming from various sources which affect the running of the machine.

Resonance is another term you'll see used and while this is related to machine vibrations etc it's mostly higher frequency resonance which affects motors and drive performance and not how much the machine actually vibrates to the feel or touch.

If I'm wrong then sorry and ignore my ramblings. . . Lol

Regards machine DB noise then most of the noise comes from the spindle/cutting tool and material type. Different materials have higher or lower sound levels and vibrations depending on density, RPM, DOC & Feed rates being cut at etc.
Stiffer machines can cut deeper and faster but make more noise/vibrations so it's not easy to compare DB noise unless like for like machines.

Personally I'd just build the machine you want without worrying about noise and deal with noise if it's an issue by building an enclosure with sound deadening materials to a DB level that's acceptable to you.