When sinuses sing together: System-level acoustic resonance enhances ventilation of the paranasal sinuses

Acoustic excitation can enhance sinus ventilation and may improve topical drug delivery, but the resonance behaviour of the coupled nose-sinus system remains poorly characterised. This study investigated whether the sinonasal cavity exhibits a system-level global resonance and whether this resonance enhances oscillatory sinus-nasal exchange. A simplified straight-duct model with asymmetric side cavities and seven computed tomography-derived realistic sinonasal geometries were analysed using acoustic experiments and compressible transient computational fluid dynamics (CFD). The simplified model showed that morphologically different cavities shared similar dominant resonance frequency, despite isolated Helmholtz-resonator estimates predicting different frequencies of 489 and 575 Hz. Experimentally, both cavities resonated at 380 Hz, while CFD predicted a shared resonance at 366 Hz, confirming coupled system-level behaviour. In realistic geometries, all sinuses within each model shared a dominant global resonance frequency, with geometry-dependent values ranging from 264 to 350 Hz across the seven models. Surgically modified geometries with widened ostia also exhibited shared secondary resonance peaks between 541 ± 2 Hz and 871 ± 3 Hz. CFD reproduced the experimentally measured resonance behaviour in the realistic validation cases with errors below 4%, and reflecting inlet/outlet boundary conditions matched the experiments more accurately than non-reflecting conditions. At the global resonance frequency, pressure fluctuations, ostial velocity RMSE, and normalised intra-sinus air-mass fluctuations were amplified, indicating enhanced oscillatory sinus-nasal exchange at low input amplitude. Findings show that the sinonasal cavity behaves as a coupled acoustic network with geometry-specific global resonance behaviour, supporting patient-specific acoustic tuning for future acoustic drug-delivery strategies.