An important microscopic parameter of a fiber is its diameter.
The fiber diameter is directly related to the sound-absorbing characteristics
of the material. Table 1 shows a comparison of the average
fiber diameters of several types of industrial fibers measured
using electronic microscopy techniques. In general, the diameter of
natural fibers tends to be larger than the diameter of synthetic fibers
obtained by extrusion. Figure 3 shows some scanning-electronmicroscope
images of samples of hemp, kenaf, cotton and polyester
fibers. It is evident that natural fibers have more irregular shapes
and variable diameters compared to synthetic fibers.32,33