What's going on with Major's bark? =(

Today I heard Major bark, and it was really weird. You may be familiar with the different types of barks your dog has, I'm sure they are common between all dogs.

Major's are:
-the normal bark, usually happens when somebody's coming. Sounds like your regular dog bark
-the whiny bark, happens when he's upset, or if at night he gets twisted around the tree with his cable
-the growly bark, when its more like a "woof woof" and deeper, if something is really bothering him

Now, this bark I heard today sounded like a REALLY weak whiny bark. It sounded as if he had a real sore throat. Michael, my brother, said he heard it yesterday. This is the first we've EVER heard it and I don't know if something is wrong or not.

I don't know where it could have come from/what it is, etc, but these are the possibilites I have thought of:

-from different dogs (he was at the kennel for about 12 days)
-him hitting one of his vocal chords?? on something
-barking too much its sore (though, he's barked at the farm for like 45 minutes straight at squirrels before, its never happened)
-eating something ??

Did Major stay in the kennel recently? He may have contracted something there. Also, can you see him while he's doing it.
My Lab/mix, Maggie makes many more wierd sounds than my shep/mix
Smokey. It might be a Lab thing.

Yes - he did stay at the kennel, we picked him up on Jan. 2. He is up to date with his kennel cough and other shots though. My dad heard him bark yesterday and said it sounded slightly less 'hoarse'. (The word he used, I'm not sure if its correct, I guess it kind of sounded hoarse.)
I haven't heard him bark since then.
Yes I could see him when he was barking, everything appeared normal except for the sound. He's not lethargic or acting sick at ALL, not one sign. So I'm not sure. :confused: