We use air blowoffs at work which previously just had a 1/8” hole in a pipe plug. Screaming little SOBs. We cut some slots around the sides to let more air out and it really did the trick. If it’s plastic pipe you could experiment around with a slip on piece to see what works best. Slots, holes, muzzle brake style?
I want a calliope end so I can play circus music out the roof.
Or a slide whistle. I always wanted a slide whistle, to do my own sound effects. And I just learned that a professional quality one in only $11.