Turbo noise

It can make a huge difference in a quiet house early morning/ late at night even on tiles. I'm been lucky enough to be able to afford a Tacx Smart bike which has the same innards (magnetic flywheel) as the Neo 2/2T and it it's virtually silent except for its free hub.  On the Neo the noisiest thing will be your bikes drive chain and gear changes which mostly can be avoided using ERG mode.

DCRainmaker has videos covering the noise from all modern turbos. From memory the Tacx's and Wahoo's edge it over the Elites. 

My mates tacx neo 2 on a concrete floor is silent, literally the only noise comes from his drivetrain (which is hardly anything), it's bonkers quiet! (But they are pricey..)

My Wahoo Kickr Core is very quiet indeed.  The only noise is from the drivetrain.  I got lots of benefit from my old Elite Chrono Fluid and a speed/cadence sensor, but Zwift/smart trainer has been a whole new ball-game to the point that a virtual ride or event has become something I choose to do, rather than something I do just because I can't get out on the roads. 

I've got the original Elite Drivo and my drivetrain is louder than the turbo. New trainers are even quieter. Fans are louder than both, but that noise doesn't travel far.

I went from a wheel on trainer to a direct drive about a year ago and it is noticeably quieter (not that it was too bad before). I would keep an eye out on ebay or facebook marketplace as you can sometimes pick up a bargain, although a lot of used ones for nearly new prices. 

I enjoy the added realism of the gradients on the smart trainer, but I still feel you can have a good workout using a speed/cadence sensor and basic trainer doing intervals. 

Before Christmas my direct drive trainer (JetBlack WhisperDrive) went kaput in the middle of a 10 day 1026km charity ride, so I borrowed a mate's Bkool wheel-on trainer (a model I previously owned) to finish it. In terms of noise output from the trainer per se I found the difference absolutely negligible. However, this was in my kitchen which is stone-flagged, the DD is definitely much quieter than a wheel-on if used on floorboards, even with a carpet over them, the vibrations of a wheel-on trainer are far greater and set up a big hum; the reason I bought a DD trainer was because my next-door-neighbour (nicely) complained that with our Victorian semis sharing floor joists it was like having a washing machine in her living room when I was using the wheel-on model.

TLDR: worth it if on floorboards, if your trainer's already on a concrete or stone floor probably not.