I had the unfortunate experience of having an accidental discharge of my MP40 FS in my master bathroom (and trust me I kicked myself in the *** for months on how f..king stupid I was, but it did increase my gun safety awareness 10 fold, I use this experience to teach others the importance of gun safety) but I will tell you it was loud, very loud. I can't really tell you if I have any permanent hearing lose but even to this day I still get a sudden loud ringing in my ear about once a week.