I have 8 Rena canisters, all of which are quiet. If you have one making noise, then something's wrong.
Can you describe the noise you're hearing? Knowing what noise you're hearing may help us figure out what's wrong so we can help you fix it.
Otherwise, I'd recommend doing a regular maintenance on it, including cleaning out the impeller and the casing around it, and clean and then lubricate the o-rings. Check the intake and outflow hoses to be sure you don't have a snail caught in them. Just do an overall maintenance check, and you should be able to find out what's wrong and take care of it.