I opened and checked the dryer. The video is very helpful and I had no problem opening it. The idler and roller seems ok. Frankly I don't know how to tell if they are bad or not. The idler looks normal. I spin the roller and it works. The drum belt looks old and has a lot of crack on the inner side.
There is a cushion around the round front opening that looks old and its thickness is not even. The upper part of the cushion (about half, i.e. the upper part, of the circle) is almost more than twice thicker than the lower part of the cushion.
What do you think is the problem for the noise? Is it the belt or the cushion?