A #ow starting from a shock tube is accompanied by a bow shock wave and a head ring vortex. This #ow pattern is responsible for impulsive sound generation when the jet impinges on the wall. This problem is studied experimentally and theoretically in the present paper. In the experiment a conventional shock tube of internal diameter D"65 mm is used. The jet issuing from the shock tube was visualized by means of a Schlieren system. The instantaneous pressure was measured at the wall at several distances from the axis of the jet. Subsonic and slightly underexpanded jets with #ow Mach numbers in the range from 0)65 to 1)14, were considered. It was found that the shock wave, after re#ection at the wall, generates a toroidal sound wave due to its interaction with a ring vortex. The sound wave splits into two pressure pulses when it passes through the vortex core. The vortex alone generates a sound wave when it reaches the wall. The theoretical approach is based on the Euler equation. It allowed the authors to predict the main characteristics of the considered #ow satisfactorily.