Humming capacitor?

[Tree Penguin]

Hi, what can cause a capacitor to hum?
My active speakers are producing a lot of hiss (tweeter) / low humming (bass speaker) and the cause seems to be a capacitor as it vibrates a little and makes some noise doing it. Is it because of ageing?
Thanks.

[don rigby]

what you are hearing is 60 hz hum probably due to bad capacitors in your amp.
proof: put your speakers on another system and see if it goes away. double check by putting proven speakers on your system.