I don't know of any studies that directly compare the hearing of wild and domestic dogs. I suspect the reason why there is so little research into that is because most scientists assume that their hearing is about the same.

Dogs evolved their amazing sense of hearing because it helped them reproduce more effectively. For example, better hearing might have enabled a dog to hear predators coming at greater distances, it might have allowed them to find more prey to feed to their puppies, or it might have let them hear new mates who were so far away that other dogs couldn't hear them. All of these things would let a wild dog with better hearing produce more puppies.(Remember that in evolution, reproduction is the only thing that matters. Survival is only important because it lets you reproduce more. A species in which all the animals survive to old age but never reproduce will go extinct.)

That's how wild dogs got their great hearing, then humans came along and domesticated some of those dogs. Humans have used selective breeding to exaggerate different traits in different breeds of dogs: Dachshunds forgetting into rat holes, greyhounds for running fast, etc.

I've never heard of anyone breeding dogs to have worse hearing, and I can't think of any reproductive advantage to a domestic dog losing its great sense of hearing. So, I suspect that domestic dogs can probably hear just as well as wild dogs. Excellent question!

Check out this web-site for a diagram of a dog's ear: dog's ear