Interesting article. You would think that someone might come up with different whistles that would be suitable for different situations, rescue for one, job site for another, instead of one-size-fits-all sort of thing. Like flashlights.

It appeared that they measured the distance of the sound in feet, if I was reading it correctly. Elephants communicate with infrasonic rumbles that are so low that humans can't always hear them even when they're nearby, but other elephants will pick up the 'message' over two miles away.

Sue