If you have a Neato XV series robotic vacuum, and you don’t already have one, you need to switch to the curved/spiral brush. This is the one Neato ships with the “pet” versions of the vacuum. It’s far quieter than the one with the parallel straight rubber blades. The sound of the vacuum is reduced from a dull roar to a far less intrusive sound. I can barely hear it when the vacuum is running downstairs and I’m in my office. I’ve also noticed that it also seems to pick up a lot more dust and debris. Overall it’s a huge improvement.
I ordered mine from Crucial Vacuum, part number 945-0002. Best 25 bucks you can spend on your little robot friend.