Over the past decades, interior noise from wind noise or engine noise have been significantly reduced by leveraging improvements of both the overall vehicle design and of sound package. Consequently, noise sources originating from HVAC systems (Heat Ventilation and Air Conditioning), fans or exhaust systems are becoming more relevant for perceived quality and passenger comfort.
This study focuses on HVAC systems and discusses a Flow-Induced Noise Detection Contributions (FIND Contributions) numerical method enabling the identification of the flow-induced noise sources inside and around HVAC systems. This methodology is based on the post-processing of unsteady flow results obtained using Lattice Boltzmann based Method (LBM) Computational Fluid Dynamics (CFD) simulations combined with LBM-simulated Acoustic Transfer Functions (ATF) between the position of the sources inside the system and the passenger’s ears. It provides an approximation of the contribution of each noise source to the passenger’s ear locations. By identifying and quantifying noise sources, this method guides engineers at treating the main sources in confined systems, usually a daunting task experimentally.
In a first part, the accuracy of this numerical approach is investigated by comparing predicted aeroacoustics results to measured data: in a first step for a simple lateral duct with vent; in a second step for a HVAC unit in fresh air ventilation mode. In a second part, the Flow-Induced Noise Detection Contributions method is used to highlight the location and intensity of the various noise sources for the different operating conditions. In the third and last part, limited modifications are made to the HVAC system geometry within design constraints, and LBM simulations are performed on the modified design to numerically assess the reduction of the noise levels.