Hybrid source arrangement for active control of noise through apertures at oblique incidences: a preliminary investigation

Lam, Bhan, Gan, Woon Seng, Shi, Dongyuan and Elliott, Stephen (2018) Hybrid source arrangement for active control of noise through apertures at oblique incidences: a preliminary investigation. In 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling. vol. 2, International Institute of Acoustics and Vibration. pp. 739-746 .

Abstract

Active control solutions are effective in attenuating noise propagating into a room through an open aperture, whilst maintaining natural ventilation. When the noise is normally incident, an evenly-distributed planar array of control sources across an open aperture has the highest upper frequency limit of effective control compared to other source configurations. At oblique incidences, however, the performance of the planar array is physically limited by the spatial aliasing limit. Since a dominant oblique noise incidence is analogous to controlling traffic noise at the upper floors of a high-rise building, it is important to maximise attenuation performance at obliques incidences. Adapting from a double-layered edge source configuration approach, a hybrid layout of double-layered edge sources coupled with a planar array is proposed to improve noise attenuation at oblique incidences. The attenuation performance is investigated in 2D finite element method simulations. The position of the double-layer sources are largely unaffected by the wall width and the distance between source layers. At glancing angles of incidence, the hybrid layout appears to be effective up to a much higher cut-off frequency than the planar array. The results suggest that alternative layouts such as the hybrid approach should be adopted if the dominant incidence of noise is constant.

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