Flow-induced tonal noise in automotive cabins: Experimental analysis and Helmholtz resonator modeling

Abstract

Tonal noise generation within vehicle cabins due to flow infiltration through structural gaps poses a significant aeroacoustic challenge in automotive design. This study investigates the generation of flow-induced tonal noise within a vehicle cabin through an integrated experimental and analytical approach. Tonal noise was first localized using the steered response power with phase transform algorithm applied to a multi-channel microphone array, which identified the dominant source region near the side mirror-body junction. Pressure measurements at multiple locations—including the cabin interior, door panel, and side mirror cavity—were conducted under various yaw angles and ventilation modes in a wind tunnel environment. While pressures at individual points did not reliably predict tonal noise, a critical pressure difference of approximately 105 Pa between the cabin and door cavity consistently marked the onset of tonal components. Based on the observed geometry and flow conditions, the side mirror cavity was hypothesized to behave as a Helmholtz resonator. To test this, the cavity was modeled using geometric parameters and excited using a Corcos-based representation of turbulent boundary layer pressure fluctuations. The predicted resonance frequency closely matched experimental observations, validating the hypothesis. These findings demonstrate that tonal noise arises from flow-induced excitation of resonant cavity structures and emphasize the importance of pressure gradient control in vehicle design. The results offer practical guidance for mitigating tonal noise through flow path and structural geometry optimization.