This is old but still actual topic. I don't know why but seems filter manufacturers don't care a bit about vibrations of their pumps. Most of the filters uses the same concept with magnetic impeller and of course this causes vibrations to the head which is very, very hard to dampen. For example I have Ultramax 1500 and I can sound proof impeller screaming noises if present, but no way to dampen low frequency hum from the unit. If placed into a cabinet, this amplify the hum multiple times cause low frequencies scattered over the room and I can hear it even upstairs on several places which makes me nuts. I've put it on a foam but vibrations from head are transferred into a cabinet even though there is no direct contact with the walls. Not sure if there is material which is thick enough to dampen this noise and can fit into 80x40 cabinet. Outside it feels more quiet because the hum is not that strong. I guess I will need to drill holes into my 40cm wall and put it outside the living room to get total silence.
Manufacturers should put more attention to eliminate vibration from the pump itself. I can't understand there are not many complaints on this topic and everywhere I read how the filter is silent. Even "dead" silent in some cases. Well, those people must be completely deaf or ignorant. If I look at videos on youtube every single filter on video is producing hum and most are around 40 - 50 dB which is definitely not silent!