Not my calling circle but a large room filled with students! If you or a guest speaker have problems projecting your voice in a classroom or other setting please contact OET. We have for loan a portable voice amplification system. The device, ADDvox7,” increases a user’s vocal volume up to 15db without any feedback. The ADDvox7’s lightweight headset microphone picks up the slightest whisper and can be comfortably worn for extended periods. It is worn similar to a fannypack and the amplifier is lightweight and provides 14 hours of continuous use. ” ADDvox7