Kesan Lapisan Berliang dan Nisbah Keluasan Plat Berlubang Terhadap Ciri Akustik Serabut Sabut Kelapa Sebagai Bahan Penyerap Bunyi

This research was conducted to study the acoustic characteristics of coconut coir fiber which has high potential to be used as a sound absorbing material. To increase the acoustic performance of coconut coir fiber at low frequency, porous layer was installed in front or behind with the aims to increase the value of surface impedance. The perforated plate with a different ratio of perforation was used as a backing plate for the coconut coir fiber. Samples were tested according to international standard ASTM E 1050-98 for measurement of sound absorption coefficients. A 1 mm perforated plate made of aluminium backing with coconut coir fiber, showed the sound absorption coefficient with frequency between 2750 Hz and 2825 Hz with a maximum peak value of 0.97. The value perforation ratio of perforated plate could reduced the sound absorption coefficients at high frequency. The decrease in the coefficient in sound absorption occurred when the perforation ratio of perforated plates reached below 0.22. However, the use of perforated plates can increase the acoustics performance of coconut coir fiber at lower frequencies. Good agreement was obtained from the experimental results and analysis using the equivalent electrical circuit approach used to calculate the noise absorption coefficient. This shows that the equivalent electrical circuit approach can be used to design and optimize the acoustic characteristics of coir fiber as a sound absorbent.