There is an article in the May/June 1998 issue of Ferrets magazine on
ferret hearing that might interest you.
 
Albino mammals of many kinds or frequently deaf or hearing impaired.
Studies have shown that their parts of their hearing apparatus (the
contralateral projections from the antero-ventral cochlear nucleus) are
much smaller than those found in sable ferrets.  This is why dark-eyed
white ferrets (albino crosses) are also often deaf or hard of hearing.
 
Another phenomenon that causes deafness in ferrets is Waardenburg's
Syndrome, which is a genetic defect.  This defect shows up in mammals of
all kinds, including humans, cats, rats, mice, and ferrets.  Waardenburg's
syndrome is responsible for a number of symptoms that may not all show up,
but these include deafness or hearing impairment; widely-spaced, small,
blue, or odd eyes; and a white forelock of hair.  You may have seen humans
with a white streak of hair from their widow's peak, cats with white
stripes on their head, and rodents with head "spotches."  The "badger
stripe" of the Blaze ferret is attractive and often sought after in
ferrets because of looks, but the coloring may be accompanied by hearing
impairment.  Similarly, Panda ferrets (think of a BIG blaze that spread
farther over the head) can have the same problem.
 
There are some technical tests used on Dalmations that show promise in
testing ferret hearing, but my favorite "cheapie" is the vacuum cleaner
test (turn it on and see if you get a reaction).
 
Hope that helps!
 
- Erika and the Terrific 10 (including DEAF Misty, a blaze female rapidly
  turning into a dark-eyed white as she ages!)
[Posted in FML issue 2762]