Audible means capable of being heard. If something happens audibly, that means it's audible. When a sound is indistinct, or simply not loud enough, you might complain about its audibility (creators of TV dramas don't seem to care about the audibleness of their product).
Audible is also an Amazon salesline, which enables subscribers to listen to a huge range of audio books for a monthly fee. They're currently offering a free trial.
From Story Idea to Reader is now available as an audio book (see my last post for more info) so if you'd like an audible version of the writing advice offered by myself and Rosemary J Kind, sign up now!