A neighbour is building an addition a mile away. I can hear the sharp crack of every hammer blow. Woodpeckers use the same strategy to mark territory with sound. So the back of a hatchet against a solid, dead tree could certainly work.

I also like the idea of a steel spoon on a steel pot. Forget aluminum though.

Used to be that people in bear country carried a pen launcher, with a bunch of bear bangers and a few flares.

I have seen air horns that have their own built-in pump. Seems to me that sort of noise would carry, and get attention. Possibly the best alternative.

I've never used a Jetscream whistle. Wonder how it compares.

I should add that my hounds don't really respond to the Fox40 whistle. It takes a lower pitch. A flat whistle brings them in much better. Go figure.

P.S., Following up on an older S&R thread: "If a bra falls in the forest, does anybody hear?" (Bad, bad Doug. Goes and stands in corner.)