Additive Manufacturing: A Novel Method for Developing an Acoustic Panel Made of Natural Fiber-Reinforced Composites with Enhanced Mechanical and Acoustical Properties

Table 9

Comparison of acoustic absorption coefficients between natural and synthetic fibers [70].

Fibers	Thickness (mm)	Absorption coefficient
		250 Hz	500 Hz	1000 Hz	2000 Hz
Rock wool	50	0.29	0.52	0.83	0.91
Glass wool	50	0.45	0.65	0.75	0.80
Polyurethane	50	0.30	0.68	0.89	0.79
Polystyrene	50	0.22	0.42	0.78	0.65
Kenaf	50	0.48	0.74	0.91	0.86
Hemp	40	0.59	0.60	0.56	0.52
Coconut	35	0.28	0.40	0.64	0.74