just as a thought here as i am not totally sure what your asking for if you only want to play this sound to one person not the room and not everyone eho joins and they have the sound file on there pc and they want to hear it each time they join then i would script it on there pc as something like an ON Notice event

Code:
  
On 1: NOTICE:*crankit*: {
if ( $nick == nickname ) && ( $active == #channelname ) {
/splay soundfile 
}
}
[color:blue] the above goes is your friends remotes   [/color] 

on 1:JOIN:#channel: {
 if ( $nick == nickname ) { /notice $nick crankit }
}
 [color:blue] the above goes in your remotes  [/color]


the reason i say this is i dont know how you would keep from hearing the sound yourself by using /splay someone else prolly has much better ideas than this and also might know of a way to mute the sound or something of the sort