Noises are one of the few areas where we really have to be there to hear it for a diagnosis.

Start by taking the dryer apart by inserting a screw driver in the gaps between the top and front near the edges which will allow you to flip up the top. The with manually turn the drum and see if you can tell where the sound is coming from.

If you need to dismantle the dryer further, take off the back service panel, release the belt and then take off the front (two screws hold it on).