Helmholtz resonator with a spiral neck

The Helmholtz resonator (HR) with a spiral neck is studied in this paper both theoretically and numerically. The proposed modified HR uses a spiral duct to lengthen the neck in a small space. The curvature effect of the spiral neck is transformed to an equivalent straight tube and the overall attenuation performance of the HR is then derived. The theoretical results agree well with the simulation predictions, showing that a HR with a spiral neck can achieve high sound reduction within a small space at low frequencies. Furthermore, it also displays several resonance frequencies at higher frequencies.