Finer fibers lead to more effective sound absorption due to the greater number of fi­bers per volume, more contact area, and more tortuous channels.61 Furthermore, the presence of finer fibers decreases the chances of pore connectivity62 and increases the flow resistivity. Additionally, finer fibers can be vibrated easily compared to coarser ones; and cause acoustic energy dissipation.61 Jayaraman et al.,61 Lee and Joo,62 and Koizumi et al.63 reported higher sound absorption with finer fibers. Koi­zumi et al.63 found substantial increase in absorption properties with incorporation of micro denier fibers. Technical fibers generally have Poisson distribution of fiber diameter which may be taken into account during modeling.18 One disadvantage with plant fibers is that they generally are coarser than petroleum-based fibers due to the fact that a technical plant fiber is comprised of a great number of elementary fibers as seen in Fig 5.6.