I got 6 Filstar’s and they all make very little noise right now. I do agree that straight out of the box, they are kind of loud though. IME, the canister needs some minor adjustments and tweaking.
The magnetic impeller is the only moving part on the Filstar's besides the water itself. This is the only possible part that is making any motor noise whatsoever. You can find this out for yourself by taking the top off the canister and removing the impeller (and the quick disconnect hoses), then plugging it back in. Nothing is moving and it is virtually silent.
Leave it plugged in and slowly put the impeller back in. You’ll feel the magnetic force start to take over when you get the impeller close enough, at this time you can just drop the impeller back in the hole. If you get an electrical shock don’t blame me. Anyways, the impeller is the only thing making any noise.
Fish water slime usually helps lube up the impeller to make it less noisy. If this is canister is going on a new tank, it may take awhile for the slime to build up on the impeller. If you have really hard water, maybe that could cause a noise problem too.
Like what Raskolnikov said, opening up the holes on the spray bar helps lessen the whistling noise too.
Burp the canister.
When you think the canister if full of water, take a flashlight and look for the waterline on the canister. If you can see a waterline that means there’s air in it. To get the air out, unplug the canister, and then release one of the clamps holding the top on. Let a little bit of water spray out through seems, then close tightly. Now plug it back in and let it run for about a minute. You might have to do this 3 or 4 times if there is air in the hoses. The quicker you can unplug the canister then release the clamp, the better.