Abstract

We investigate sound absorption of oil palm panels using an impedance tube constructed to comply with the requirement of ASTM-C384-04. Palm trunk is cut along and across the vascular bundles. The process yields disk-like wood panels with a thickness of 10-14 mm. The panels are then drilled to form an orderly square arrangement of multiple radii and depths of blind holes. In addition, the absorption of checkerboard-patterned groove is also under consideration. Finally, the combination of through-hole and grooved panels are determined for the absorption. The frequency range is limited to 300-2000 Hz. The results indicate that the sound absorption of the cross-cut wood is greater than that of the parallel-cut panel. The depth of the holes helps improving the absorption in high frequency range (>800 Hz) by twofold. However, different depths for blind holes of 3-mm diameter show slight difference in sound absorption with the maximum value at 10-mm depth, ∼25% improvement as compared to that of 5-mm depth. The combination of the through-hole panel and grooved board allows ∼80% of sound to be absorbed. This finding displays another possibility of utilizing palm biomass for sound absorbing applications.