Playsound when a player leaves and area but not when they enter

Solution 1:

Well first I would set up a clock and make the following commands in this order:

  1. /scoreboard players add @a[x=,y=,z=,r=] play 1 (@a[x=,y=,z=,r=] Is the location of where you want it at)
  2. /execute @a[score_play_min=1,score_play=1] ~ ~ ~ /playsound paspawn @p

  3. /scoreboard players set @a[score_play_min=2] play 2

This would play the sound one time when they are at the location and then it would never play the sound again. Hope this helps!