The fan should be almost inaudible unless you are in a quiet room (definitely quieter than a MacBook Pro when its fans spin up). It runs continuously at a constant speed. We chose this particular fan for its quietness.
Since our QC procedure currently doesn't check how loud the fan is, and our production area has some ambient noise, it's possible that your H9000 has a fan which is out of spec and needs to be replaced. If you contact us via email to email@example.com, we can arrange for this. I apologize – this isn't something we anticipated.