I am looking for something louder for sessions. Is there anything that has clear tone like the Oak but is louder?
Overton, Copeland, Busman, Burke, and Sweetheart to name a few.
Oaks are on the louder end of the cheapie spectrum IMO. Perhaps a Feadog would cut through a bit better?
Or try playing out the side of your mouth closer to your ear. The other sessioners can probably hear you better than you can so keep that in mind too.
this is as loud as your going to get 
Not to gainsay you sir, but, I just got a Thin Weasel in blackwood that is actually louder than my other high Ds. I really wasn’t expecting it to be so loud. The bore is even larger than my Overton. I have to say that it is my absolute favorite high D. It has a reedy dark and mysterious bell note and a stunning, soaring second octave. I guess I just got lucky; however, I have learned that the Thin Weasels are very consistent. Best, Cyril.
yea i am leaning towards wood myself------ the only good tin i like is a Clarke----------i am thinking the delrin busman might be a good one----------------i love that reedy sound i bet your TW is fine ---------how is the sweetheart doing—
sindt
I recently purchased a Burke aluminum session whistle in D and it’s great. Good volume. I highly recommend getting one. 
Reyburn. It’s that cylindrical metal with plastic (Delrin) head style, taken to it’s best expression.
An Overton is a different animal. An incredible animal - but not Oak/Generation style.
The sweetheat is a dear. If I were you, I would contact Paul Busam, sooner than latter. I would ask him for a blackwood, Best, Cyril.
I’ve rarely met a whistle in a session that needs to be louder. They can carry through a loud bar room, across another room and up a flight of stairs. The only two instruments clearly discernible from this distance were the whistle (an Oak BTW) and a tenor banjo.
It’s probably louder than you think. I’d ask those you play with about the need for a louder whistle before buying - nothing worse than plonking down serious money only to be told you’re too loud now.
Eric
I used to play an Oak in sessions before I got my Burke, and it’s still my favorite cheapie. The problem was, if the session was loud, I couldn’t hear myself, and then I would instinctively blow harder to compensate, and as you probably know by now, an Oak can’t handle that.
I would get a Burke–they can take gentle play or agressive play without squawking.
Jennifer
I’ve played Burkes for some time. I didn’t realize how loud they are until someone else joined the band for a while and played one. As she was tuning up I thought “WHAT THE HECK IS THAT!!” I looked over and was shocked to find it was a brass Burke. I’ll admit that I wear ear plugs when playing, but I had no idea of the penetrating power of the whistle sound. I should though. As a teen in Ireland I noticed that when I went to the pub’s toilets and heard the music from a distance, the whistle stood out.
Right. I think the term “session whistle” has created an unnecessary expectation of what a whistle should be in a session to many players. Certainly a well-balanced whistle would help you be able to hear those lower register notes better without the higher notes breaking the windows and pint glasses but the whistle does not need to be heard above everything else. As mentioned above, it carries quite well from a listener’s standpoint. The session I frequent has the restroom upstairs and when I mosey on up, the whistle is usually very easy to hear above the murmer of other mixed fiddles, flutes and guitars.
i cool right now on whistles -i got some ‘Flow’ in the bank for that special something that might pop up here i dont need alot of whistles - i went through that phase already -------my next trick could be a sax , bodhran , flute, special whistle--------------who knows -i blow my dough, then, i have to stress out selling it -i am laying low -till that bad boy pops up