As a rule of thumb, any plumbing thing made by a Geman or Swiss firm will have taken NOISE MADE by the device into consideration and been developed with the criterion that minimizing noise is important. Faucets and toilets, for example.
It is hard for any firm to claim noise reduction as an achieved goal, for a number of technical reasons (e.g. definition of noises, definition of measurements of noises and comparative noises to scale against, etc) and marketing reasons (it's too negative, like saying fewer people have died in this particular car...) so the best hint you get is when they talk about quality and comfort...
Exaggerating slightly, I'll say that in that part of the world, I think the various "players" allow subjective criteria to be part of the process, whereas here (North America), regulatory agencies are only allowed to set rules on life-and-death concerns and publish studies on the hardest facts verifiable. Even Consumer Reports barely touches on noise as a factor.
Notice how NO plumbing store ever has working toilets for you to listen to? I installed two wall-hung toilets recently, with all the same parts but different bowls. The Duravit is quieter than the Catalano. Water flows smoother in it both at the peak of the flush, at the beginning, and also at the end, when filling.