The robos I've had experience with (a whole bunch now, hah, as a friend of mine has a few) are not very vocal. If they do squeak and chirp, it's not frequent and usually pretty quiet. I discovered yesterday that one of my girls is a talker--she was squeak-chirping to herself while walking around, I was very surprised. You might frequently hear tiny quiet whistling sounds as they explore something excitedly, but you really need to pause what you're doing and listen hard to hear it.
None of mine have been chewers. They are occasional nibblers, but most of their wooden toys are in near-pristine condition after long use.
Mine do dig and scrape at corners. They love digging, especially if you give them deep layers of bedding, but they will also dig at corners, litter boxes, and any random toy bases. When some of mine were moved to an aquarium, they periodically like scratching at a particular corner (which is pretty quiet), as if they can dig through it
Wheels can be noisy. I found that the pitter patter on plastic is in itself quite loud, because of how
fast robos run. Especially if you have more than one robo, then it's constant hitting of plastic, stopping, and continuing. I've tried silent spinners with them too, but it wasn't any quieter because Leela and Dora, being older and able to control them, roll very fast. so the spinners actually wobble about the axel and make a plastic-hitting sound. Leela on her spinner was louder than Leela on her Rolly. Flying Saucer with a robo has not been quiet, despite putting tissue between the axel and the top. Wodent Wheels have been quietest, as the track is much bigger, but I don't find them safe for more than one robo.
I've just received three mini wooden Karlie wheels, which are supposed to be the quietest, but have not had a chance to test them out, as the laquer I covered them with is still drying.
Overall, my Lucy is much quieter than my robos, because she doesn't dash everywhere like crazy and her wodent wheel is quieter. Oh another thing is when robos run around, if you have a ceramic food plate, they will hit it on the way and make that sound too periodically.