Originally Posted By: djlmwh
A quality whistle is tough to beat because it is reasonable, reliable, and reusable....
....It may be that there is a better whistle waiting to be designed -- one that transmits on a variety of frequencies: a low signal to attract interest at a distance, along with the shrill pitches we are accustomed to hearing as a call for help.

I agree with the whistle and that was what prompted the thread. Other than beating on something like a pot or the sheet metal of a machine I could not think of many other sound makers a person needing help might have with him.
I think the range of ideas shows how hard it is to come up with something better than the simple whistle as a carry along device.
Some of the ideas were interesting though and in some situations they might have merit.

Like I said in the post, just throw some ideas around and see where we get.
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May set off to explore without any sense of direction or how to return.