I can see the nostrils. I can see the eardrums. I have heard a frog, it was at night. I think it was sending a marrying message. Late on a warm summer night, I have heard frogs croaking to each other behind my home in the ponds in the park that borders our property.
Frogs have vocal sacs which swell up when the frog is calling or croaking.
It sounds very deep and quick. We have a green tree frog in our class. When it croaks it sounds like a dog barking. I like the way it sticks to the sides of the tank it's in. I learned that the male green Tree frog sounds like a cow bell.