The LEVO utilizes various motors during use which produce sounds that might not be familiar. A gear motor located under the heat plate uses magnets to turn the magnetic stirrer that sits inside the reservoir, producing a dull buzzing sound when in use, and is normal. The drain valve is controlled by a motor that will produce a noise when plugged in and when in use. Additionally, the lock is controlled by a motor that sounds similar.
If there's a sound you are hearing that just doesn't seem right, or if you are still experiencing trouble with your LEVO you can submit a warranty claim here.