Been on a range at the SHOT show where everything up to a .338 Lapua was suppressed. Behind the line no ear protection was necessary.
The fact that it is altered to not be ear damaging, isn’t that a good reason to make the rule be to ask people to put suppressors on their guns when target practicing? Think about it. If I was living out in rural PA, and you wanted to practice shooting in your yard? Wouldn’t you want to lessen whatever was audible to me say, a ways down the road, for courtesy’s sake. I would!