Experimental study on the standing-wave tube with tapered section and its extremely nonlinear standing-wave field

A standing-wave tube with tapered section (STTS) is evolved from a standing-wave tube with abrupt section (STAS) whose abrupt section is replaced with tapered section. The research is intended to compare the acoustic properties and the extremely nonlinear pure standing waves of STTS and STAS. The acoustic properties of the STTS are studied with the help of transfer matrix. It is proved, like the STAS, that the STTS is dissonant standing-wave tube. With its dissonant property, the 181 dB extremely nonlinear pure standing wave is obtained in the STTS excited at its first resonance frequency. Then the comparative experimental studies on the saturation properties of the extremely nonlinear standing waves are carried out in the STTS and the STAS with the same length. It is found that the STTS can suppress the harmonics and meanwhile reduce energy loss of the standing wave more effectively. Compared with the STAS, under the same voltage of the loudspeaker, the STTS obtains a higher extremely nonlinear pure standing wave. Moreover, it is found that under the third resonance frequency, the frequency of the third harmonic in the STTS is close to the seventh resonance frequency of sound source impedance, to which the valley value of the sound pressure level transfer function corresponds, and that the third harmonic increases rapidly with the increase of fundamental wave and it tends to saturate.