I saw a cheap plastic toy in a charity shop yesterday. It was a hammer, where the handle was a whistle and the head was a bellows. When you hit the hammer against something the bellows would drive air into the whistle and make a squeak.
The un-obvious feature of the design was that it had two fipples, one on each side.
The toy didn’t work, mainly because the bellows head was too stiff to drive enough air.
But I don’t see why a mouthblown instrument like that shouldn’t work. I can’t think why you would want it, but it ought to be feasible.
Anybody done it on a real instrument?
I think it’s (relatively) common with native American flutes (see here), but that is with two windways. I’ve never seen it with a single windway, but it does sound intriguing, especially if you could offset them slightly to get some interesting effects. The only drawback I can think of is that it would take a LOT of air and, unless you DO want a bit of dissonance, a lot of fine tuning. Sure would be an interesting experiment!
Pat
That type of toy seems fairly common. Maybe I just travel in the wrong circles.
I made a whistle with two windways/windows some years back but just one fipple . I used a normal whistle body and scale - so not like what Plunk111 linked to. And I think I’ve seen another whistle done in a similar manner here at one time but cannot recall who produced it. Possibly Daniel Bingamon? Don’t remember at this point.
Aaahhhaaa! Are 3 Fipples better than one?
I wasn’t going for the train whistle effect, just a louder whistle. My initial motivation came from working as a referee for soccer matches when my kids were youngsters. I used a Fox 40 whistle for that work which has two windows and blades. It’s quite loud. So I thought I’d try to see what would happen if I made a similar structure on top of a musical whistle. It was a little bit louder than my usual whistles. It took more air. My mouthpiece design was clumsy and too big. But it wasn’t difficult pitch wise at all. I had expected it would just feel like a whistle with a large window and not be particularly well focused. But I was surprised that it was ok in that regard. It was a fun experiment. And I got that thought out of my head til just now. Thanks. 
Feadoggie
Actually, the Fox 40 (Classic or Micro) has three fipples, tuned to 3 consecutive semitones approximately B7-Bb7-A7. Yes it’s loud (around 120 dB), and the semitone clash creates some very nasty beat frequency undertones (difference tones) which make it seem even louder. Indoors in a small room, a Fox 40 will take the top of your head off if you’re not wearing hearing protection.
Hmmm? I know that the Fox whistle produces three tones but I can only find two windows (and no fipple! being strictly pedantic here and ignoring recent common usage 
). I thought the third tone was either a harmonic or the result of three air chambers. Where’s the third “fipple”? I’m not being argumentative here just hoping to find some enlightenment. I’d offer to cut mine up to find out but I passed it on to my son when he started wearing stripes.
I could never believe that the Fox 40 whistle was developed as a whistle for basketball referees. It is way too loud indoors, IMO. Of course I was not refereeing the NBA or the Final Four games.
It’s underneath, Feadoggie. It’s the window pointed to as “air chamber” in your bottom diagram. Each of the windows produces a different pitch.
The B7-Bb7-A7 gives three difference tones: 431 (~A4), 222 (A3), 209 (Ab3). And it’s the last two which set up that low phantom “buzz” that feels like someone drilling into your skull. 
I really like the Fox 40 Micro for EDC (Everyday Carry). It’s like a squashed flat version of the Classic, fits easily in the pocket, and nearly as loud (~110 dB). Makes a great signaling whistle for getting someone’s attention, or a sonic defensive weapon up close.
Chuckle! 
Ok. Thanks for that MTGuru. I’m at a loss here. 
I should have noticed a window on the bottom of the whistle. Mine may have been a two chamber Fox whistle. Hopefully my son still has it and we’ll check it out. It was plenty loud though. The whistle I cobbled up had two windways and two windows separated by a wall of maybe 1/8". I was concerned about getting pronounced beats and other phase issues but it worked well enough as an experiment.
You are right Fox whistles would make a good signaling whistle and they are seemingly tough as nails.
Feadoggie
