Noise Transmission through a Glass Window excited by Low-Speed Turbulent Flow

Rémi Bessis (1) , Yves Gervais (1) , Laurent-Emmanuel Brizzi (1) , Janick Laumonier (1)

1 PPrime [Poitiers] - Institut Pprime [UPR 3346]

In order to improve on-board automotive acoustic comfort, we investigate the effects of vortex dynamics and unsteady flow separation outside the lateral window of a car (the A-pillar) on the noise transmission through the window. Different mechanisms are expected to contribute to the transmitted aerodynamic noise. One is related to the acoustic excitation mainly generated from the transfer of kinetic energy of the turbulent volumetric flow structures into acoustic energy, then transmitted through the window. A second mechanism consists of direct hydrodynamic (turbulent boundary layer) excitation of the window. Experiments have been performed in an open low-speed wind tunnel including a forward-facing step geometry in order to generate vortex shedding above a thin glass window. An anechoic cavity under the glass allows capture of the transmitted sound. Surface-pressure fluctuations and outside velocities (PIV) were estimated simultaneously. Correlation-based signal processing was implemented to link flow structures to acoustic transmission. Attempts to separate the contributions behind noise transmission involving energy-based filters (POD, LSE), along with the variations of timescales and lengthscales on the flow are also presented and discussed.

Domaines: Acoustique [physics.class-ph]

Rémi Bessis, Yves Gervais, Laurent-Emmanuel Brizzi, Janick Laumonier. Noise Transmission through a Glass Window excited by Low-Speed Turbulent Flow. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810931⟩