Studies on Sound Absorption Properties of 3D-Printed Open-Porous PLA Material Structures for Noise Suppression in Hybrid Electric Vehicles

Noise, vibration, and harshness (NVH) of a vehicle are important factors for vehicle users and essential for successful commercialization of HEVs that can provide both substantially improved ride-comfort and reduced energy-consumption. The noise and vibration behavior in hybrid vehicle is significantly different from the conventional vehicle. In conventional vehicles, certain noise phenomena are masked by the engine noise. However, when the combustion engine is turned off in hybrid vehicle, these noise components can become dominant and annoying. While driving, the low frequency interior noise below 2000 Hz causes the main component that irritates the auditory acoustic sense. In order to remove this low frequency noise, passive noise control methods were used using sound absorbing materials or isolating the noise source. However, it is found that the sound absorbing materials are effective only for high-frequency noise compared to low frequency noise. The present work deals with the sound absorption properties of open-porous Polylactic acid (PLA) material structures that were produced using 3D printing technology. The material's ability to damp sound was evaluated based on the normal incidence sound absorption coefficient and the noise reduction coefficient, which were experimentally measured by the transfer function method using an acoustic impedance tube. The present investigation showed that the 3D printed openpore structure are efficient to reduce the noise by absorbing sound.