Some questions.
1) How hard was the strike?
2) How long was the contact (Was it an elastic or inelastic collision)?
3) Was there a momentary pause after he got hit?
4) Was there a complete seal on his ear hole (the pressure wave does more damage when it has nowhere else to go)?
5) Did his head move with the blow?
A double ear slap is not a finishing technique it is a set up or a distraction for a finishing technique.
1) Full power downward diagonal strike from a padded stick
2) Momentary
3) Yes, but since he just took a full power shot to the side of the head from a stick, the cause is difficult to assess to to the earshot or just getting his bell rung. The sticks we use are about 13 oz, quite heavy for a padded stick, I have TKO'd guys through a fencing mask before with one.
4) No idea, but since it burst his eardrum, I would say the damage was done
5) Yes, quite a bit.