Annihilation of shocks in forced oscillations of an air column in a closed tube

Effects of a periodic array of Helmholtz resonators on forced longitudinal oscillations of an air column in a closed tube are examined experimentally. The column is driven sinusoidally at a frequency near the lowest resonance frequency by oscillating bellows mounted on one end of the tube. Frequency responses are obtained for small and large amplitudes of the excitations. While the array lowers the resonance frequency and the peak value, its dispersive effect, i.e., the dependence of the sound speed on a frequency, can annihilate the shock effectively.