I have 3 Sequence pumps and they are all extremely quiet including the Hammerhead. Has yours always been noisy or is this a new problem? Are you sure that it is "vibrations" resonating or possibly cavitation?
I had a similar problem with my RO/DI booster pump resonating (serious hammering) through my house pipes and found a way to solve that by adding a 4' length of 1" PVC between the supply and the pump. What was happening is that the pump is trying to draw off more water than it is being supplied. I have heard this can also be accomplished with a check valve, and to note for your reference, I have a clear check valve just after the output of my Hammerhead. I don't particularly trust it to hold back a siphon, but it gives me visual confirmation of flow and I believe cuts the noise of the pump/flow down going into the system.
Something else you should consider is the size of your pipes. many reefers will install one size larger pipes between the pump and its water source as well as after the pump. This allows more flow and less cavitation, from what I understand. You may not be giving the pump all the water it needs. They are very loud when priming or during cavitation so that is an area worth looking into. There is a guy on RC, Dale (tinygiants), who has a real firm grasp of liquid flow dynamics and I would suggest contacting him if you can't figure out the problem on your own. Unless the pump is somehow damaged, the problem is probably in some measure related to how it is plumbed. HTH!