not sure if i understand your question. you have 3 buttons and you want them to play the same sound when any one of the buttons is clicked, right?
if so.. the problem would be that in your code you only have one event listener
you have to add the event listeners to the other buttons which are calling the playF function, basically copy the line but change the play_btn to whatever the instance name is of your other buttons is.
and if i misunderstood your question, .... i don't know, good luck. lol