It's not uncommon that a clothes dryer produces some noise when it runs. In most circumstances, the noise is from clothes tumbling in the drum, which can create a thumping or rattling sound, depending on what you're drying. However, if the dryer starts making loud noises -- ones that you haven't heard before -- this could indicate a problem with the machine.
Your clothes dryer should be installed on a stable flooring surface so it doesn't shake when it tumbles clothes. If the floor is the slightest bit uneven, the dryer is liable to thump and pound against the floor when it runs. The noises can be especially loud when drying a large laundry load. Try to move the dryer side-to-side with your hands. If it moves easily, adjust the dryer's four feet at each of the corners until the machine is completely level on the floor.
If you hear a loud rattling sound when the clothes dryer is on, stop the dryer in mid-cycle to inspect the drum's contents. Perhaps coins or keys have come out of trousers pockets and are banging on the drum's walls, or you forgot to remove a belt from a pair of trousers, which can cause a loud pinging noise after each drum rotation. Remove the metal items from the machine to stop the noise.
Problems with a drum belt can generate a loud, unfamiliar noise in your clothes dryer. A drum belt is made of rubber and can stretch over time. When this happens, it can slip from its place around the drum's centre, which causes the drum to turn erratically and sometimes slam against the cabinet. If the belt snaps, the noise can become even louder and more frequent until the drum eventually stops spinning. Examine the belt's condition. If it's either out of place or damaged, replace it.
A drum bearing is what holds the drum in the cabinet. It's the drum's main support mechanism. Excess use of the dryer can put strain on the bearing and ultimately cause it to wear. If this occurs, the drum might shift downward in the cabinet and rub or knock against its sides. The contact can cause it to produce a loud squeal or knock, depending on how far down the drum has dropped. A defective bearing can't be replaced. Swapping out the worn bearing will eliminate the noise.