Frogs and Toads have a noticeable external eardrum or tympanun, located just behind each eye, with no outer ear like humans. This conducts the sound directly to the hearing structures just behind. These eardrums are usually disguised with the colouration of the skin.
Frogs don't use hearing to locate prey or danger, but listen to the other warning calls or mating calls of other frogs. When a frog comes across a threat they will call to warn other frogs of the danger. But hearing is mostly used in mating and territorial activities.
Haha, I have one in the eye of a squirrel, if that counts
Back on subject, that photo is fantastic. He's really clear and doesn't seem to be bothered about you at all. I know you couldn't do anything about it, but it's a bit of a shame about the huge blade of grass cutting him in two... Still, well done!