FOX40 CMG Sonik Blast whistle with string A referee and coach's whistle. The latest model from FOX : the Sonik Blast CMG official + string . The latest technology used in these whistles makes them the most effective in their class. This model emits a sound power of +120 dB. The whistle has two chambers and four sound resistors, making it much louder than its predecessors, the Fox Classic. The whistle is packed in the original blister!