Pretty sure that’s true, since some of them can’t actually capture how loud a gunshot is. For example, I saw a video of a guy shooting an unsuppressed 45, which came out to 113.8, then when suppressed with a commercial can, 87.4. But I was kind of surprised and disappointed to never see any numbers, which would be more useful than audio. Even without professional equipment, you can still get a general idea of the reduction levels I would think.