I am the wife of oxfordcircus. I don't post a lot at all, but I feel that I must add to this thread.
I talk for all my animals. I answer questions, make requests, hurl insults, and generally provide one-liners, extensive diatribes, and anything and everything in-between for them.
Their voices coincide with their personalities, and I've noticed that as the animals age, they evolve into "old people" voices. Belle, our elderly border collie, for example, is quite crochety in her sarcasm and her voice has become strained like she's fairly long in the tooth.
Jane, our weimeraner pup, is scared of everything and often we notice her shivering from fear or cold or whatever else she can think of. As a result, her voice is very high-pitched and quiet, almost a whisper.
We have two Kats. Being a dog person, I simply take care of and show affection for the Kats, but they get on my nerves verily. Mind you, I sure wouldn't want anything to happen to one of them, but Kats are just not as good as dogs. As a result, the Kats have essentially the same voice, and it kind of sounds like the voice you would have if you were a Kat with a brain the size of a butterbean.
The beta fish even has a voice. Rainbow is always extremely angry. Whenever anyone looks at her, she puffs up with rage. She's a year old now, and has always done this. Maybe she does not like living with us. I don't understand why! I feed her several times a day, change her water often, and talk to her! Anyway, her voice sounds a lot like a Kat's, only muchmuch higher and even dumber.
For example. Tonight I cleaned out Rainbow's tank, and I accidentally dropped her in the sink. She slipped down the drain into the disposal, and I had to stick my hand down in there and fish her out, but it was okay because I picked her up lickety split and heaved her into her clean water. Then she flicked her whole body in a furious rigor and said, in a very high, dumb fish voice, "Screw you, lady."