It's not loud. No rattling at all. birzzz definitely rattling isn't normal. I would pop the cover... something probably just needs to be snugged up.The fan is making sound
but it's all fan noise. I don't think the compressor makes much sound at all. The fan sound is consistent not annoying. With that said, for me, it doesn't matter anyway as this unit now allowed me to move my fermentation to my back hobby room. I was keeping them in our rec room which has it's own heating/cooling. But it's also our home theater area. I don't want ANY sounds in there. The controls work fine. It's keeping both within a degree.
The best part.... once your fermentors are at temp the thing almost never runs.
I will wait for the support to contact me before opening up the unit. They sate that it will void warranty if you open it up without their consent.
I can tell you that my girlfriend finds my hobby quite annoying and noisy...