Advanced science and technology makes the Sonik Blast CMG the most efficient pealess whistle in its class! Precise whistle chamber calibration assures pure frequency performance; lest effort, crisper sound. 4 sound-producing resonators built into 2 chambers. Flawless patented pealess whistle emits sound power that exceeds 120 dB. Extremely easy to blow; cannot be overblown. Superior clear loud blast can be heard over long distances and ambient noises. A must for emergency protection, onsite disaster management, search and rescure. Recommended for anywhere without a ceiling! Works wet or dry!