An investigation on interior noise reduction using 2D locally resonant phononic crystal with point defect on car ceiling

Interior noise, as one of the indicators of automotive NVH (noise, vibration and harshness) performance, has been associated with an increasing importance in ride comfort evaluation. This paper presents a new method of interior noise reduction based on phononic crystal theory. Considering the lightweight requirement, the car ceiling plate is divided into nine regions to determine where the phononic oscillators should be mounted. By leveraging the acoustic contribution analysis of each region, the phononic crystal is arranged in the region that contributes the most to interior noise, bringing out the best attenuation effect in its bandgap. However, it is noted that at certain frequencies, the vibration of the ceiling plate or other body plates, which exhibits negative contribution to interior noise, should not be attenuated due to their beneficial effects. Thus in this paper, a point defect is employed for the design of a two-dimensional (2D) phononic crystal structure to preserve the negative contribution part of the plate’s vibration at specific frequencies. The validity of the proposed method in interior noise reduction is verified by simulation. Moreover, the error analysis is implemented and an optimization scheme is proposed.