Not knowing anything about your dryer, such as model number or age and when the last time it was given a good tune up. I would say that the pulley that works as a belt tensioner needs to be replaced. My best suggestion would be to give your dryer a good tune up which includes replacing all the rollers and pulley, the belt and a good cleaning. This would probably cure your noise and it would also reduce the chance of a dryer fire.
Answers & Comments
Not knowing anything about your dryer, such as model number or age and when the last time it was given a good tune up. I would say that the pulley that works as a belt tensioner needs to be replaced. My best suggestion would be to give your dryer a good tune up which includes replacing all the rollers and pulley, the belt and a good cleaning. This would probably cure your noise and it would also reduce the chance of a dryer fire.
I hope this helps