This is a model (working, the torch is half a meter behind the nozzle edge) of a pulse jet engine.
It has a very characteristic, loud, low sound. More like a hum with infrasound inclusions.
It works on Butan-Propane mix and use safe "water lock".
I tried to use Ethanol (C2H5OH), but it need turbine, didn't work in this version of the jet engine.
Built from plumbing fittings and all sorts of metal scraps )))