Wise Turtle Publishing

I'm making a couple of spell/attacks for my character.
These are chants or songs that only effect those who can hear her, but I do not know if this would affect allies as well.
If this does would this be a unique flaw or perk, and what would be the endurance drain increase/decrease on it?

It's amazing how i can spot you, before you asked me.
next time please contact me first?

The easiest way is to give it a Cancel of "characters who cannot hear."

Whether you want it to affect allies or not is up to you, but if you do, Area Effect x3 should do the trick of affecting everyone in a nearby radius.