"C J Campbell" wrote:

Exposure to prolonged engine and propeller noise
definitely will cause hearing loss in humans, just as
prolonged exposure to rock and roll will.

Then it follows that it *could* potentially cause hearing loss in dogs as well.
Just because a dog bark is loud and they carry on with it for extended periods
doesn't mean that has the same effect on their hearing as a constantly running
engine at that specific level.

Dogs, however, can and do create noise that is just
as loud and prolonged without any apparent hearing
loss on their part,

Such as? and where is this study?

Most dogs, in fact, do not appear to hear all that well.
It is too easy to sneak up on them, for example, if you
do it from downwind. They will not respond to
whispered commands.

Really? I've owned many dogs, and I'm pretty light on my feet, and I've never
been able to sneak up on one until they were well into old age and *obviously*
hard of hearing. And as far as not responding to a whisper, I can whisper the
word "cookie" while she's asleep and my JRT jumps up and runs to the jar. I'd
say your statement depends on the dog in question.

Unfortunately, there don't appear to be any serious
studies measuring hearing loss in dogs due to noise
hazards. Anything veterinarians have to say in this
regard may be no better informed than what any dog
owner would say. It is all based on speculation and
anecdotal experience.

On that, I completely agree. Even a veterinarian's opinion *is* JUST that on
whether or not taking a dog in an airplane on a regular basis without providing
some form of ear protection would or would not be harmful to their hearing. As
said in a previous post, it all boils down to what you are comfortable with,
since the dog really has no choice (other than to make it extremely unpleasant
for you if he/she is unhappy!).

--Shirley