The article has several important implications including but not limited to:
1) Pick the right whistle for the right season and terrain.
2) Not all whistles are created equal (no surprise there, eh?).
3) There may be places where others cannot hear your signal - be aware of them.
4) More research is needed to identify the whistles that perform best during a specified season and on specified terrain. For instance there is nothing in this article about how the whistles perform on open seas.

Perhaps Doug has some input here. Could this be a job for the folks at ETS?

I was not that surprised on some of the results. For instance I have noticed for a while that my supposedly cheapie silver Metal Pea whistle sounded a lot louder than the Fox-40 Rescue Howler in my PSP. That said there are still many good reasons to stick with the Fox-40 as it is a pealess design that won't freeze to my lips in extreme cold.

Of course the most important lesson here is to be aware of the capabilities and limitations of our equipment and ourselves.