Audability refers to the quality of being hearable. You might say, for example, that someone is a great presenter for the most part, but the audibility of her voice is an issue because you can hardly hear her talk.
Audibility is, in many ways, literally in the ears of the hearer. A sound may be loud enough and in the right frequency range to be heard by many or most people, but not by someone with reduced hearing acuity. And the audibility of certain sounds often depends on the type of animal that's listening. Dogs, bats, dolphins, and many other animals can hear higher sounds than people can. Elephants can hear sounds at lower frequencies than people can hear.