I have been using the Avalung for the past 6 years. Its a great tool to have for backcountry and even inbounds skiing. They make a "fog horn" noise when breathing through it. No need to be alarmed thats normal. The main thing is that you should have it in your mouth while skiing, this may seem awkward at times, but after some use it becomes a normal feeling. A must have for the backcountry enthusiast.