I've done my due dillegence and searched the forums for "no audio" in my outputs.
tapping the . on the numberpad plays the audio.
Using Ram preview - i hear my audio
The layers are not 'muted' on my timeline.
In my render queue i do in fact check the box for "Audio output"
I've even tried to render just an mp3 - silence.
In what format it your source audio? What codec/format (other than .mp3) are you setting for your render?
The source videos are all mp4s, There is also 2 mp3s in the comp.
In theory, you should be ok, but as a troubleshooting step, you may want to try converting all of your source formats to losslessly compressed formats, and replacing your assets with the lossless versions (i.e., use Quicktime PNG or Animation compression at best quiality for video, and uncompressed .aif or .wav for the audio).