Be aware that these sound systems effectiveness diminishes with use as the animals become accustomed to it, kind of like people that live next to train tracks or near airports tune out the noise that would drive many others crazy...
I have never had an issue like that, and this is not all that...
You would probably need more like a garbage can of water, and regardless rats can stay afloat/swim for up to 3 days, so they are not going to drown anytime soon after they fall in...
Poison is a dangerous proposition around chickens... Rats/mice are known to carry food and stash it in places, if the chickens happen to find a stash of poison it can be lethal... Also chickens can and do kill rats/mice and if they consume the poisoned rat/mouse again it can be lethal...
in addition to trapping and killing the rats, you can sprinkle cayenne powder on the chicken food to deter the rats from eating it... Birds lack the pain receptors for capsaicin so they won't even notice it's there except for the slight vanilla flavor, won't hurt them at all, and it will...