I don't have noise restrictions where I live, but I do love my quiet. This little machine is less noisy that the name brand I used previously, and works better. It is not as loud as my electric toothbrush. I think you'll be quite happy with it, and the times in the future when you don't use it, you'll miss it.
The Panasonic oral irrigator has a pulsing sound. It is not noisy at all. It's just water that shoots in between your teeth at two different speeds to remove food particles. There is no buzzing or roaring-just water like water running from a faucet but only softer and pulsing in a narrow stream. Any operational tool will have some vibrating or pulsating sound but not to a point of irritation that I have found. I hope you find this helpful and, by the way, this does not make the noise of an electric toothbrush.
When the motor starts there is a bit of a shrill sound to it. I use it often very early in the AM and the wife is a very light sleeper and has never been awakened by it. But it is a distinct sound to it.