
Hi - BAER testing is to determine hearing. Dalmatians are prone to congenital deafness, which reputable breeders are trying to eradicate by only breeding from animals which can hear in both ears. About 10% of dalmatians are deaf in one ear, which doesn't affect their lives at all but rules them out of a breeding programme.
Here is more information about the
BAER test. It is the only way to deaf-test a dog: if people say their dog can hear because it reacts when they squeak a toy or clap their hands are fooling themselves. Even totally deaf dogs have been known to react to that because they sense the movement of the air.