Mine isn't particularly loud. It's slightly louder than non covered gears in 2wd buggy but to notice it you'd have to be pretty picky.
One thing I discovered a couple of years ago is that all pinion are not made equal. I have a compete set of pinions but not from the same manufacturer and some of them are super loud ! They didn't harm the spur but my god the noise makes it very worrying. The loudest I have is one that looks like the titanium ultimate racing ones. I can't confirm you that's the brand as it's not written on them and I bough it 5-6years ago so I can't remembrer, but it's the loudest hands down by a lot !