A pulse jet operates by using a metal flapper valve on the front end of the combustion chamber which opens to let air into the tube and ignites it, the combustion pressure slams the flapper valve shut and the thrust goes out the tail pipe creating a vacuum in the combustion chamber which opens the flapper valve letting in fresh air which ignites and slams the flapper valve shut,(pulses), ergo pulse jet. As everyone has said, VERY noisy and the tail pipe gets red hot.
We flew a control line pulse jet in a school yard where there was some construction going on and the jackhammer operator asked us to leave cause we were too noisy.