Just an idea
I also have several HD's run from USB caddies, one of them a Seagate PATA 2.5" drive does bleep in distress, if it does not have an additional USB power connection plugged in.
Edit:[You will need a connector with one connection for the hard drive & power + data connector USB at the computer end, they are often supplied with the caddy.]
Could this be the cause of the bleeps ?
CAT III