Here’s the pulse jet running on propane. I found it’s better to start on propane then turn the fuel pumps on. That’s when it really makes a LOT of noise. You ave to blow air in the plenum, or combustion chamber, to build pressure so when it ignites it starts the pulsing process. The frequencies created by pulse cause vibrations. You can see the aluminum wheel chock that’s sitting on the trailer near the fender start to move. It makes your chest vibrate too. | Paul Koehler