This paper presents the nonlinear gas oscillations generated in oscillating horns near resonant frequency. The effect of horn shape on the pressure waveform is studied. The horn is subjected to a longitudinal harmonic force. The nonlinear wave equation for isentropic flow is solved in time domain using Galerkin method. Both transient and steady state oscillations are obtained. The amplitude and waveform of pressure oscillations are strongly affected by the horn shape. In the cylindrical horn sawtooth-type shock wave is formed. It is found that by changing the shape of the horn, the amplitude of oscillations and waveform can be altered. In the present study, four different types of horns are considered: catenoidal, exponential, conical and sinusoidal. © 2003 by M. Tyagi and R. I. Sujith. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.