I had the same problem but it's not the Helix. I originally used the Helix on a rack and I would hear that buzz. I contacted who I bought it from and I was told it has something to do with the electrical current in my house. He said it happens rarely and I was the second or third person that had the problem. I hooked up a ranco up to the rack and it worked fine. I still use the helix but only on my incubators. Seems to work fine just not on the rack with the flexwatt.