Just a tip for the store/franchise owner. When your team member can't hear what your customer is ordering through the drive thru, please don't tell them to say,"you need to speak up!" That to me comes off really rude and disruptive, especially when they're shouting back at you.
I'd prefer a more calmer and pleasant approach like, "I'm sorry, I can't hear you. Can you please repeat that?" And maybe we'll raise our voice just a little so you can hear us better. If your intercom can not pick up normal talking decibels, then maybe that is what need improvements.