This study develops an absorber containing abaca fiber (Musa Textiles) and epoxy resin as a binder. The ability to absorb sound energy is related to the pore’s size present in the absorber. One of the methods to create porosity is to vary the length of fiber, which is 1, 10 mm, 15 mm and 20 mm. Before the fiber is cut to be certain length, it is treated employing NaOH alkalization and acetic acid hydrolysis. The characterization carried out includes density, morphology and absorption coefficient measurement using impedance tubes. Moreover, the fibers are measured for the density, then continued to determine the porosity and air flow resistivity using the Konzeny-Carman equation. The air flow resistivity parameter is utilized to determine the absorption coefficient using Delany-Bazley model. The value of the absorption coefficient from experiments using impedance tubes and based on theoretical analysis shows a similar trend curve. The results show that the fiber with the length of 20 mm exhibits the highest sound absorption coefficient.