Exactly the same problem I have Paul. The hissing sound coming from the nozzle is the loudest thing in my shop. But, I just try to ignore it because there is no "free lunch" so to speak. Something has to make noise. My hearing started going downhill when I was a teenager. I used to go to the drags and loved listening to the Art Arfons jet dragster as it went by me. Then, in the Army, on maneuvers one time, I was unlucky enough to be standing between to M48 tanks as they fired simultaneously. The air turned orange and I couldn't hear for an hour. Then constant ringing in my ears. I sold tools for almost 40 years so I was in and out of all kinds of shops and it was always noisy. I have tinnitis too. So, at 75 years of age, I don't even think about trying to "save" my hearing. I never wear any kind of hearing protection. I just try to make everything I do as quiet as I can. The Fein vac and my dust control system works great but the hissing noise is still bothersome.