This paper is concerned with an investigation of the nonlinear behavior of sinusoidal plane progressive acoustic waves of finite amplitude in air at a frequency of about 21 kHz. The various stages in the distortion of the wave have been experimentally studied and the results compared with theoretical models. The experiments were done in a tube 5.5 m long and 8-mm internal diameter with an absorbing termination. The acoustic source used was a prestressed piezoelectric sandwich transducer with a titanium stepped mechanical amplifier, the small end of which was the piston that produced the high-amplitude motion inside the tube. This source was capable of generating a nearly pure sinusoidal wave at sound pressure levels up to about 155 dB (re: 0.0002 μbar). Interestingly, as compared to previous reports on this field, the use of a high frequency has allowed the study of all the propagation regions (including the old age region) of the wave using a short length tube.