If you could hear me, you should've said something!
You heard my fart, didn't you?
I understand it sounds harsh, but I’m up to my neck in lame excuses.
You've seen 聞く by now hopefully. This is similar, but instead of meaning "to hear" it means hearable (or to be audible). Just think about that こえ hanging off there as the voice you can hear.
The reading comes from 聞く, so if you know the reading of that word, you can apply it here.