Abstract
The aim of this research is to observe the acoustic performance of absorber-based biomass fiber-reinforced polyester resins that were experimentally associated with the design of tailed cavity resonator inclusion, i.e., the cavities are partly in the form of a narrow slit. The model of electro-acoustic resonators and several treatments were developed and became the bases for understanding the changes of acoustic reactance in the new structure. Variations in the inclusion cavity and the addition of a narrow slit were tested experimentally using an impedance tube technique based on ASTM E1050-98 and ASTM E2611-09. The improvements of acoustic performance were conducted by single and multiple cavity tailed inclusions with the addition of a Dacron fibrous layer and back cavity. The experimental results showed that a sample of 15 mm single tailed cavity kenaf fiber had higher sound absorption and wider broadband frequencies than did the hemp fiber, with a peak on 0.31–0.32 between 1.00–2.00 kHz. Meanwhile on multiple tailed cavities, the 30 mm hemp fiber had higher and wider broadband frequencies than did the kenaf, with peaks on 0.45–0.63 at frequencies between 1.75–2.10 kHz. It can be concluded that the tailed cavity inclusions could improve performance. Compared to the coco-husk with resonators in previous studies, the tailed cavity was a little bit lower, but the tailed cavities hemps and kenafs samples showed good sound absorption performance with lower band frequencies capabilities.
Highlights
Natural fibers play a significant role as commonly-used materials; the acoustic field has taken advantage of these fibers for various applications
The results showed a porosity increase due to the increment in the kenaf fiber percentage, while the increment of the kenaf fiber caused a reduction of the tensile strength
The sound absorption performance of the six specimens before treatment is presented in continuous lines (A0, C0, and E0 indicate untreated, 15 mm thickness coco-husk, hemp, presented in continuous lines (A0, C0, and E0 indicate untreated, 15 mm thickness coco-husk, hemp, and kenaf respectively, while B0, D0, and F0 indicate untreated, 30 mm thickness coco-husk, hemp, and and kenaf respectively, while B0, D0, and F0 indicate untreated, 30 mm thickness coco-husk, hemp, kenaf respectively), while the treatments are shown in the dash-dot lines (A1H-Tailed, C1H-Tailed, and kenaf respectively), while the treatments are shown in the dash-dot lines
Summary
Natural fibers play a significant role as commonly-used materials; the acoustic field has taken advantage of these fibers for various applications. Acoustic material is highly demanded in the architectural sciences due to its applications in buildings in which sound performance criteria are significant factors. Biomass fibers and other porous materials play important roles in the acoustic sciences, most of them are brittle, flammable, and susceptible to mold and weakening in mechanical strength, factors which preclude their use directly as noise control materials. Scientists used various types of binders and additives to increase the mechanical strength and performance. This method was successfully applied, but it caused another constraint regarding the decrease in acoustic and sound absorption performance.
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