Investigation on a Duct Noise Control Method through Membranes in Tandem

Duct noise control is an important practical problem. This paper explores the vibro-acoustic mechanism of duct noise through the membrane in tandem. Validity and feasibility of the proposed analytical model is demonstrated by comparing existing simplified models and full direct aeroacoustic simulation solved with the CE/SE model. It is shown that the coupling effect between two membranes in tandem is not negligible to predict system response. Moreover, introduction of multimembranes is important or even the only efficient way to apply this passive control method in practice.

Impact of the Sub-Grid Scale Turbulence Model in Aeroacoustic Simulation of Human Voice

In an aeroacoustic simulation of human voice production, the effect of the sub-grid scale (SGS) model on the acoustic spectrum was investigated. In the first step, incompressible airflow in a 3D model of larynx with vocal folds undergoing prescribed two-degree-of-freedom oscillation was simulated by laminar and Large-Eddy Simulations (LES), using the One-Equation and Wall-Adaptive Local-Eddy (WALE) SGS models. Second, the aeroacoustic sources and the sound propagation in a domain composed of the larynx and vocal tract were computed by the Perturbed Convective Wave Equation (PCWE) for vowels [u:] and [i:]. The results show that the SGS model has a significant impact not only on the flow field, but also on the spectrum of the sound sampled 1 cm downstream of the lips. With the WALE model, which is known to handle the near-wall and high-shear regions more precisely, the simulations predict significantly higher peak volumetric flow rates of air than those of the One-Equation model, only slightly lower than the laminar simulation. The usage of the WALE SGS model also results in higher sound pressure levels of the higher harmonic frequencies.