Audio on After Effects

Voice over

Sound effects

music

google>youtube to mp3

royalty free audio

record sounds yourself

music from itunes

audio file format

AIFF-mac

WAV-pc

mp3

m4a-files wont work in after effects

flac-big files dont work in after effects

Audio level=Volume

you can key frame it to fade in and out.

To crop audio move mose pointer over duration bar and drag.

Use audio levels to fade in and out

To loop audio need to select the sound and click on interpret footage.

Also when rendering important that the audio box is checked.