I was recently shopping for a vacuum to replace a couple "brand name", upright, bagless machines acquired over the years from Walmart or similar vendors. My two main reasons for replacement were the bagless systems were very dirty- emptying them involved holding it at arm's length over a trash can, taking a deep breath, opening the trap door and dropping the dirt into the trash in a cloud of dust. The other main complaint was the noise. Jeez, those things were awful. I couldn't stand to be in the house when one of them was running. The upright design requires moving the weight of the whole machine while vacuuming- very tiring.
Given the Dyson's reputation for being a premium product, I checked into them. Bagless- ugh! And on-line reviews by both pros and consumers said they were noisy as all get-out. And then there were all those refurbs...
I eventually settled on a Miele C4. It's very quiet, cannister type (much easier to use because you don't have to keep moving the weight of an upright back and forth), uses bags that close themselves up when you take them out of the machine. The air rushing through the nozzles makes more noise than the motor unit. My cats will sit undisturbed while I vacuum until the nozzle is within 1 m of them, then they just move out of the way.
I've been doing a lot more vacuuming since I got the Miele. It is hard to believe it can move as much air as it does an be so quiet.