Fish can 'hear', but also they feel vibrations through the water. S'why submarine pings can upset whales, in water vibrations and sounds get magnified and travel a long ways depending on power. Also how humpback screams confuse school of herring enough they can't communicate with each other.
I've dealt with this problem too, since I like loud music with a good bass, but my tanks are on the same desk with the speakers.
My advice is to get headphones, which is my solution. Big awsm ones so I can have things loud. Or move your speakers so vibrations dont travel directly through the wood/surface of whatever your tank is on to your tank.
Otherwise chances are your fish does get drowned in a constant vibrating hum which can stress them out. A big indicator is horizontal black stress stripes down the body, or a paling in color. Still, I try not to risk it with my guys and only have the music loud every so often or use my headphones.