The ACR is very thin at 1/4 inch (1.0" x 2.0" x .25") - I keep the one I tested in my EDC neck pouch under my shirt. Here's the spec page for the ACR WW-3/Survival Res-Q Whistle. In an earlier post, Blast said he liked his (though he misspelled ACR in that post). The ACR is widely listed online in the $1.35-$3 price range.
Given your cited criteria, you might also look at the whistle from TOPS knives.

• TOPS is just as thin as the ACR WW-3/Res-Q Whistle, though longer (1.1"x2.75"x0.25") vs. (1.0"x2.0"x0.25")
• TOPS was much louder in the 2008 test (ACR was 109/111 dB adult/child, TOPS was 123.5/117.3 dB adult/child )
• TOPS had a lower pitch ( 1700 Hz in this YouTube video vs. 2800 Hz "live", per FFT Analyzer.
• Both TOPS and ACR were rated "vary easy to blow" in the 2008 tests.

Click on the photo here to see the TOPS in top, bottom, and side views, or
view this Youtube video to see it from all angles.
The TOPS Knives whistle page includes a pretty reasonable direct order price for qty 5 (shipping included),

I have no personal experience with them. The JetScream was measured at 109.3/112 dB adult/child in the 2008 whistle test, Part 1, pretty much at par with the ACR, though the JetScream was rated a bit hard to blow.

Thanks, rafowell. Excellent info.

They don't seem to know the Storm is a pea (not pealess) whistle.

Also, I'm fully not buying that yelling/screaming carries the farthest. The loudest I can yell will not come anywhere close to carrying as far as my Storm whistle.

Yes, the Storm pea is a little subtle.
Your results aren't necessarily in conflict with theirs.

They were in a heavily forested environment, which they said reduced the whistle range considerably from what it was over clear land, and seemed (based on my quick frequency testing) to favor lower pitched noise.

I would expect the Storm to outdistance the yell/scream over clear land, based on the 2008 whistle test dB results, at least.

There are lots of other variables with the human voice (and the whistle, for that matter): timbre, volume, listener hearing loss (both permanent, and temporary from whistle testing).

In any event, the NZ folks were recommending a whistle, not a yell. They didn't state why, but the classic reason is that your voice wears out very quickly with loud yelling.

From my summary of the 2008 Part 2 whistle test report:

"One contender in the 2008 Pt 2 test was an adult human yell: 110 dB try 1, 107 dB try 2, 104 dB try three - affected voice, larygnitis next morning. Get a whistle!"

(In a separate post, that tester (Kevin) mentioned having laryngitis for two days afterwards).

I have a ACR, Fox40 Micro and Sharx...the Sharx sounds a bit louder and has a lower pitch than the Micro(I covered my ears). The Sharx is slightly easier to blow, but its about twice as thick. Both fox's can be submerged and blown immediately, as the water clears. The ACR is about 1/3 the thickness of the sharx, and is loud, with 2 distinct pitches. Both fox's are louder. The ACR is easiest to blow. The ACR does not clear well. It takes quite a bit of air to clear and has a bit of water in it that makes the pitch higher. It has to be shaken to get rid of the water.

Interesting. Thanks for the field tests. And welcome aboard.

Thanks... I don't know if this was referenced before but http://www.youtube.com/watch?v=h9Gn8uZNX-c

All of his tests show the whistles to be around 94 db, which is far below what the manufactures claim...

How does a sharx compare with a sonik blast and storm?

I have the Fox Sharx, the Fox Sonik Blast and the Storm. The following review is subjective, as I have only blown each whistle ONCE without ear protection.

The Sharx and Sonik Blast are about identical loudness. The Sonik Blast has a smaller footprint. However, the Sharx has a friendlier shape and is a work of art to me. These whistles have approximately 2 volumes: silent and screeching loud.

The Storm is the loudest and seems to allow more control over loudness. However, the Storm is huge and bigger than it looks in Internet pics. The Storm has a pea that provides an oscillation sound, which is absent in the Fox whistles. The pea may be a concern if you are in frigid conditions because the pea might freeze. I don't know because I don't take my Storm into freezing conditions. Actually, the Storm is so big that I find myself not taking the Storm anywhere.

In my everyday carry bag is a Sharx. Around my neck when I'm snowboarding is a Sharx. Around my neck when I'm biking is a Sharx.

Thanks very much... which is the easiest to blow? Its not going to do you any good if its not with you when you need it.

Interesting how the Storm is louder because the db levels claim otherwise. 120+ vs 106.

From where did you get that 160 db number?

The maker of Storm claims 130 dB.
http://www.stormwhistles.com/storm.html

The maker of Sonik Blast and Sharx claims 120 dB.
http://www.fox40world.com/index.cfm?pagepath=PRODUCTS/Fox_40_Sonik_Blast&id=15806
http://www.fox40world.com/index.cfm?pagepath=PRODUCTS/Fox_40_Sharx&id=15861

I just blew all three. They all seem about equally easy to blow. The Storm has a lower frequency and an oscillation because of the pea. Depending on the environment, the Storm may or may no carry farther. The Storm is a heck of a whistle. I just wish it wasn't so big.