Review on Portable Voice Amplifier with Wired Headset Microphone Speaker - Louder Sound with Mask On, 18W 4400mAh, Bluetooth Support, Waterproof for Outdoor Activities, Teachers, Tour Guides - Whisper M800 by Erin Dudley

My wife is a horse trainer and typically uses a wireless headset when training in indoor riding arenas, but she often trains outdoors in circular paddocks, open riding arenas, parking lots or even trails. Apparently sound systems are not available in these areas and this voice amplifier suited their learning needs perfectly. She likes the strap or belt clip option. The battery charging function is also good since your phone is always without power when you are on the go. The audio is clear and loud enough to be heard by your students within about 100 feet or so.