Abstract: Standing-wave tube with abrupt section (STAS) is a dissonant standing-wave tube whose higher resonance frequencies are not the integral multiplies of the first one.Through the optimization and the dissonant property of STAS,the 180 dB extremely nonlinear pure standing wave field is obtained at the first resonance frequency and 177 dB at the second resonance frequency.At the two resonance frequencies,the distortion of waveform and the saturation of harmonics are studied experimentally,and yet the saturations are not found even though the pressures are so high. Meanwhile,the nonlinear sound field is experimentally studied at the third resonance frequency,and the distortion of waveform and the saturation of harmonics are observed as the pressure approaches 170 dB because the frequency of the second harmonic at the third resonance frequency is close to the sixth resonance frequency of the STAS.