My Susato is the loudest. I had a Thin Weasel once that was pretty ear damaging.
The loudest item I own is a Sweetheart high D flute (sometimes called a fife though not a “real” Bb fife).
I call that one the “Ear Buster”. I like to use it at the renfaire.
Yeah, i hear you.
That thing honks like a trombone, but YMMV, and AFAIK that model is not being made anymore, and i have no experience with the new model. I wouldn’t say the Sweet i have is a great whistle, though. The first octave is good, but the top of the second octave is distinctly different from the rest, and a little on the hysterical side, for my taste. The loudest whistles are not always the best sounding or the best playing.
I think the Silkstone and the Water Weasel are good compromises. And as i said, the O’Briain is good enough for me right now.
I’ve been reluctant to bring the Overton to a session as it’s not tunable. My first session experience was horrific due to my (at the time) untunable whistle and, well, the other players who took an hour to mention it to me.
But I am getting used to the Overton. I think you have to be slightly more accurate than I am at the moment. I left it in my living room so I’d be forced to play it.
The Susatos sound too much like that old plastic recorder I used to be forced to play in elementary school (shudder).
Thanks for the tips re warming the whistle under your leg. I’m going to try a hat/Overton/warm leg combination and see if it helps.
I hear you on the loudness of the pub. Criminy, I really couldn’t hear meself at all. Perhaps it was a blessing.
It must be really tough to play in that position 
I usually play the Susato in a noisy session. I don’t find it sounds anything like a recorder. If it’s good enough for Sean Ryan ( http://www.eaglemusicshop.com/recordedmusic/products/details/index.asp?eagleID=3210&SubCatID=245 ) it’s good enough for me - and the price is right…
Loud whistle for a session… It’s a classic excuse to splurge on a Copeland, but a Susato will do nicely.
I think the Chieftain and don’t forget the little black whistle can be load enough for any session.
I’ve worked on this issue for quite a while. I also wanted a whistle that was easy to play, which knocks out some of the high enders that require a lot of breath. Susato is out due to tone. I had some issues with Copeland. I concluded my sage with one of Mike Burkes new “DASBT” models. When you play it alone at home it sounds moderately loud, but for some reason it penetrates in a session. Cost is $130 US. The Silkstone is also a winner. It’s a tad louder, but the tone of the Burke is slightly better. Silkstone wins by a nose on accuracy of tuning, especially the C natural.
Final comment: Sweet Pro model in laminated wood is also very good. Good on loudness and tone, but it’s not a “penetrating” tone. Be prepared to slide a few millimeters off the end to bring the bell note into tune.
All of the above whistles cost under $150 each.
Yes, what i like about the Silkstone alloy and the O’Briain Feadog is that they both have that little “pop” that goes with every note, a kind of percussive attack. In my humble experience, that little pop does wonders to help the whistle cut through pub noise.
Yes also, the Burke cuts through very well, maybe because of its pure tone.
If the Sweet Pro is non-tunable, i’d advise against it. There’s probably some natural law that explains it, but as soon as you get used to playing a non-tunable whistle, strong gravitational forces will attract to your session an accordion player who has a loud instrument that’s tuned just a tad sharp…
Hi
I have an Abell D and a C which I play in sessions. I don’t think you can go wrong it is without doubt my favorite (and I have quite a few). It is quite loud and has a round (flutey) sound. Plays correctly in both registers and has a strong C nat which I like. It takes only slightly more air than my Burkes but is not quite a shrill.
The Abell has a very short beak so if you’re used to getting the whistle a long way into your mouth and hanging on you may not like it. This may mean learning some new tricks for hanging on to the whistle when there’s no holes covered (it did for me). I live where it’s dry (Calgary Alberta) and the wood is slipperier than metal in my opinion so I have to use cream on my hands at sessions.
I think you’ll also get better at sorting out the sounds of the instruments at sessions with practice - the sound of most whistles carries over the music pretty well.
All that said the ABELL is a wonderful instrument with a unique sound and gets the most comments from other musicians and listeners.
Good luck
Paul
Hi, Paul!
Ya see, THAT’S what I wanted to hear. They just look so darn wicked; all black wood and silver. DAMB! At last the justification I need! 
Say “Hi” to Calgary for me Paul.
The single loudest high-D whistle on the market used to be my Dreadnought. I don’t make them any more, but maybe you can find one used. I sincerely doubt any other high D will equal it. Well-balanced, not too airy, and needs earplugs to play at maximum volume.
Good luck finding one. People who have them tend to not want to let them go. 
Cheers,
Bill Whedon
Serpent Music
Actually, if you like whistles on the chiffy/breathy end of the sound spectrum, a good choice might be another of Bill’s whistles, the Brassy Polly (ask for the “Brassy Polly”, not the current “Sweet Polly”).
Overall, I prefer the Sweet Polly design (lower air demand, better balance between octaves, a slightly purer tone) but the Brassy Polly is noticably louder. Be aware it has very little backpressure - not really hard to play, but the tendency is to blow a lot harder than you need to. But once I started treating mine like a Clarke original model (another low backpressure whistle) and adjusted to it, I started to really like it. Good wind resistance, very good volume, and inexpensive ($25, I think). Sounds rather like a Clarke on steroids
Disclamer: I enjoy the “dirty/husky/breathy” sound that Bill designes for. If you only like pure sounding whistles, these are probably not your best choice. (Disclamer added because this is an area where Tastes They Do Vary.)
Check out the M&E whistles. These are mad-loud and has a nicer sound (in my opinion) than Susatos. Michael Cronnolly is primarily a flute maker and he works a lot in polymer, altough all his modells are available in wood aswell. These whistles are Soprano D’s with tuning slides. Available in polymer or Cocobolo wood. I bet you could persuade him to make you a whistle in African Blackwood aswel if you prefer that wood as he probably has a nice stack laying around for flutemaking. Even tough it’s not listed as an available option for whistles you can usually talk to him. He has no problem making costomized stuff and he is a very nice man.
Website: http://homepage.tinet.ie/~mandeflutes/ (scroll down to table of contents or the direct link to the whistles)
James has got a short review with some soundsamples at: http://www.flutesite.com/m&e_whistle.htm
Cheers