On the other side, there is a compartment with a cover glued to it. The glue isn't terribly strong. You can stick a thin screwdriver in the notch shown to split it open.

Once opened the glue will not reseal properly most likely.

Inside is a circuit board and another mic, and the cable to the other side.

I did have some trouble opening this as I tried to push it open from the other side using the hole on the other side for the headband.