Noise control of outdoor unit of split type air-conditioner using periodic scatterers made with array of Helmholtz resonators

Abstract

One of the reason for which the split type air-conditioner (AC) is preferred over window mounted air-conditioner is low noise. However, the outdoor unit of split type AC produces significant noise predominantly in low frequency regime and typically below 200 Hz. The sonic crystal, which is found suitable for outdoor noise control, is endeavored for attenuating the noise of outdoor unit of split type ACs. The challenge of designing a finite sonic crystal with scatterers having low diameter and minimum number of rows to attenuate the low frequency noise is addressed in present research by suggesting a tuneable multi resonant scatterer. The scatterer is made with multiple hollow compartments in the direction of height and having perforations which is tuned using finite element analyses. At last, the sonic crystal is fabricated and acoustically characterized in an anechoic chamber. The experimental investigations are conducted by deploying the sonic crystal near outdoor unit of three split type ACs and the noise measurements exhibit that the overall noise levels reduce by ≈7 dB.