Assuming all material is allowed, in the Lords of Madness there is a feat called quick recovery that allows you to make a will save(10+1/2HD+cha. mod.) as a move action to save from the backlash of Born of Three Thunders. On top of possibly a stun/prone effect and half sonic if used with an electricity spell it also gains the sonic descriptor. Also be sure to have creaking cacophony going in the area you strike. It deafens, removes invulnerability, and adds vulnerability to sonic damage no save.
The ability does seem to stack for spell level so dragon type and an accelerate metamagic or two would increase the additional damage die for each spell level increased.