True story... all vibrators make some sort of noise, not matter what the maker claims. That said, how loud a toy is can vary a lot and while we think most vibes today are pretty dang quiet, these are toys that really keep the noise down.
When looking for a quiet toy a good general rule is that smaller and softer toys tend to be more quiet. Hard plastic, plug in wands and bigger toys tend to be the loudest. You may also find that some toys get louder with age, especially if you tend to just toss them on the floor when you are done, so be gentle with your precious vibrators!