We are looking for a solution for our riders and coaches to communicate during practice sessions.  The helmets that they wear are similar to motorcycle half helmets.  At present our coaches are using a wireless mic run through the riding arena sound system.  We are limited to only one coach communicating to all the riders at the same time and everyone else in and around the arena having to hear what they are saying.  We would like to have some individual coaching and multiple coaching going on at the same time.   Any suggestions?