The ACD can be born with some hearing problems.
This is believed to be due to the Dalmation that was breed into the ACD to
ensure their love of horses.
The ACD can be born
Bi-lateral (normal hearing),
Uni-lateral (hear out of only one ear)
Deaf
All puppies can be tested for hearing abnormalities
at the age of 5 weeks. A BAER test needs to be run on the puppies
which tests them for the amount of sound each ear is capable of discerning.
It should be noted that this is a genetic problem
that can be tested for at an early age, deafness does not happen gradually
in the ACD unless due to old age.
Below is an early article about the BAER testing, there are more
clinics around that can accomplish this test.
From the Daily Echo - Tuesday, April 4, 1995

Test of Warrigal Blue Cooma