Why does my Moffatt dryer make a sound like waterfalls?

Dryer is almost a year old. Has always had a steady, loud hum to it; now, there is a "shushing" sound when I turn it on to dry clothes (lots of heat, no smells). Tech was in and says nothing wrong, but sound is louder. No noticeable scrape marks on inside of dryer, no lint build up. Just the sound of Niagara Falls when the dryer is on to dry.