I've never used this filter, so I'm not sure on the quality of its sealings, and of how air-tight it is, but double check everything is closed well. Also, I don't think shaking it is the best idea. I have an EHEIM Classic canister filter, and it is always 100% silent and the seals are good, but if I move it or shift it over a bit, somehow it starts to gurgle and make noises. So, try leaving it is one place that is steady, and let it run for a bit without touching it. It may have some trapped air at the beginning that you will have to let it get out, therefore make the noise for a bit.