Experimental Study of Acoustic Wave Propagation through Resonating Devices

The acoustic filter effects of periodic obstructions in a square section of duct are studied experimentally. The two-microphone transfer function method is employed to measure the transmission loss across the periodic elements of different profiles. The experiments aim to measure the Bragg Stop Band and the Resonance Scattering Stop Band and their interaction. The experimental data show that the Bragg effect is spatial dependent. The Resonance Scattering Stop Band is strongly affected by obstacles and demonstrates a possibly useful interaction between the Bragg Stop Band and the Resonance Scattering Stop Band. Results also indicate that for specific situations, the overall Resonance Scattering Stop Band contribution can be dominant and effective, both in terms of magnitude and bandwidth control. The asymmetric placement of the obstructing elements is shown to be nonreversible.