Publication: Numerical and experimental aeroacoustic analysis of cavity at low wind speed
Date
2024-06-01
Authors
Hairudin, Wan Masrurah
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Abstract
Wind-induced noise (aeroacoustics) in the microphone port cavity of two-way radio is a prevalent issue that significantly affects speech and audio quality, particularly in windy conditions. This thesis presents a comprehensive investigation of wind induced noise (aero-acoustic) generation in the microphone port of two-way radio through numerical and experimental analyses. A smoke visualization test was conducted in a closed wind tunnel to observe the flow structure, while a coupled direct-hybrid Computational Aero-Acoustics (CAA) method called scFLOW2Actran was employed for simulations. This method simultaneously addresses fluid and acoustics field within a single computational framework, utilizing large eddy simulation (LES) and Ffowcs William-Hawking (FW-H) acoustic analogy. The CAA investigation focuses on analyzing noise parameters such as cavity length to depth (L/D), wind speed, and wind angle orientation. Numerical results presents pressure, velocity distributions, and noise level in the near-field and far-field regions for both original and the modified microphone port geometries. The validation of the numerical results and experimental test shows a 3 dB difference at frequency of 20 Hz, confirming the feasibility of the proposed simulation method. The findings indicate that higher noise levels are observed at a cavity length to a depth of 0.7, particularly under higher wind speeds of 4.4 m/s and wind angle direction of 45°. Regarding the microphone port modifications, the result reveal that the Helmholtz resonator port with an additional aperture provides a lower reduction of 19 dB in noise level compared to others modifications. The findings also suggest that by modifying the microphone port can help reduce by weakening vortex effects. These results contribute to the understanding of wind-induced noise generation and offer
valuable insights for design and acoustic engineers involved in the development of mobile telecommunication devices. The aeroacoustics analysis proves useful in devising noise reduction strategies and guiding improved microphone port design within these devices.