The Headers Already Sent error occurs if there is any out put to the page before the header() or session_start() functions are used.
you can use the error text to help find where the issue is on the page:
means that the output that is causing the error is in the audio.php page around line 6, probably the line before it (5).
On line 5 I see that there is a blank space after the closing PHP tag:
it is this blank space that is causing the error.
remove that blank space at the end of line 5 to fix the problem.