WAVE-GUIDE AND RESONANT SILENCERS

The behavior of a system of acoustic Helmholtz resonators in a finite- length air duct is analyzed by the method of electroacoustic analogs a nd the theory of linear electric circuits. It is shown that several se ries-connected resonators (of the waveguide insulator type) can provid e a considerably deeper cutoff at the resonance frequency than a singl e resonator of the same total volume. At frequencies below and above r esonance, this cascade of resonators turns out to be somewhat less eff icient than a single resonator. It is found that, in addition to the p ositive effect at the resonance frequency, at frequencies below resona nce, there exists a region where noise is silenced less efficiently th an even in a plain air duct without silencers. The calculated results are compared with experiment and a good agreement between them is show n.