I've been in a few Ceili bands for dances, and usually, the person who handles the band arrangements will check with the caller to find out if they have a wireless mic (many do these days) or if they need one. Then, a sound check is done before hand, during the instruction part, and again after the dance begins. There is often another Musician or a person otherwise knowledgeable of sound in attendance who can be enlisted to assist in ensuring that the caller can be heard & understood over the music.