There are basically two types of FM systems; the individual ear level devices and sound field systems. For most, but not necessarily all, APD students an individual ear level device is superior to a sound field system. Individual ear level devices include a lapel mic transmitter worn by teacher/speaker and ear level ear piece receiver worn by student. Sound field systems include a handheld mic used by teacher/speaker and ceiling speaker. Sound field systems often fail to address common issues suffered by individuals with APD (ie,, directionality, localization, dichotic listening, speech clarity, signal-to-noise ratios, etc).