I would shut anything off making clicking noises. Is it a canister filter? Maybe power flickered off and it's just air bound?
If you are indeed being browned out(low voltage), it's not really good for any electrical appliances. I've seen power drops on LI from a normal voltage of ~220v down to 190v and lower, to the point the manufacturer could not guarantee nor advise the machine operating(was during a heat wave like this), so it's possible.
Less voltage=more amps drawn
As the voltage drops, electrical appliances will draw more amps. At some point some of the appliances may just not work or could be damaged.
I know we are about 5v shy here today because of the heat, but not enough to effect anything.