Experimental evidence establishing the existence of circumferential waves in a thin‐walled air‐filled cylinder with a finite discontinuity in the shell is presented. The discontinuity is a 0.062‐in.‐wide air gap extending the length of the cylinder and the full thickness of the shell. Evidence establishing that the principle portion of the circumferential wave travels within the shell and is reflected at the air gap is presented. [Work done under contract with the U. S. Office of Naval Research.]