Metaporous acoustic metamaterials with Helmholtz resonators for enhanced NVH performance in battery electric vehicles

Abstract Metamaterials have gained an increasing attention as a way of absorbing noise to achieve improved acoustic performance on vehicles, and thanks to their novel functionalities compared to traditional designs, these structures are employed by many automotive companies as noise-reduction solutions for engineering applications. One of the key challenges for automotive original equipment manufacturers (OEMs) in the noise, vibration, and harshness (NVH) development process is absorption performance in the frequency range of 400 Hz–800 Hz. Although sound engineers use porous polyurethane in these frequency ranges, the absorption performance of these designs is limited to meet increasing customer expectations. Managing airborne noise in vehicles is particularly challenging in the low frequency spectrum, where Helmholtz resonators are widely used. The main purpose of this study is to develop a metaporous sound barrier incorporating a Helmholtz resonator, effective in the low to mid-frequency range of the spectrum. For this purpose, a frequency domain simulation was carried out to obtain the absorption coefficient, analyze frequency-dependent effects, and identify critical frequencies in vehicle acoustics. Furthermore, local resonance effects to prevent acoustic waves were investigated and design parameters of metastructure were analyzed using a multi-physics based simulation model. These results were validated experimentally using an acoustic impedance tube. The methodology is demonstrated in a battery electric vehicle (BEV) to improve airborne compressor noise during engine idling. The optimum design parameters were determined using the Taguchi design method. Finally, the performance of developed metaporous material was validated through vehicle-level tests, with results showing an improvement of 3 dB(A).