I said I would take pictures, so, I have.
These whistles are only OK, in my opinion, better than nothing, but not good.
These whistles are good, but not the best.
These are the winners.
And my favorite, is on the top of this bottom image, it seems to carry the farthest. Strangely enough, it is not hyped at all. But it is darn good.
And the biggest surprise to me, is how good the mil-spec whistle performed, on the right in the image.
We tested at some distance, against wind, water and foliage rustling noise, and even out of sight, where my brother was off a bank. We felt like these were the type of conditions under which they might be used.
Not only is volume important, but the quality or pitch of the tone, that allows the human ear pick it out from amongst other noises.
YMMV,
Marion