after trying a couple of the "pea less" whistles (one of which I lost due to a weak attachment ring), I perceive a louder sound out of a plain old brass referee whistle... I'm sure it has something to do with old age, and loss of hearing in the 4000 Hz range...but nevertheless, chose one along with a Fenix E01 and a lithium AAA cell...it does make a "clinking" sound when it rattles against keys, but its durability more than makes up for it...YMMV... top of picture