Sound absorption of warp knitted spacer fabrics based on knit structure and nanofiber enhancement

In this work, the sound absorption properties of warp knitted spacer fabrics enhanced with nanofiber were studied. The angle of connecting yarns at two different spacing was considered as knit structure variable. Also, the effect of layering on the sound absorption performance was studied. Besides that, the effect of polyacrylonitrile nanofiber enhancement on sound absorption coefficient of such structures were considered. The polyacrylonitrile nanofibers were manufactured by a single-nozzle electrospinning device using a rotating cylindrical collector. The main variable for the nanofiber enhancement was its deposition amount on the front surface of spacer fabrics. The sound absorption coefficient was measured by using the method of impedance tube. For this purpose, the samples were prepared according to the requirements, and the tests were performed at the frequency range of 500–6000 Hz on single-layer and multi-layer samples. The results showed that increasing the spacing and the angle of connecting yarns will enhance the sound absorption coefficients of samples through increasing their areal mass, thickness and porosity. Moreover, layering will significantly affect the sound absorption performance of samples. Furthermore, nanofiber enhancement increased the absorption of sound at all frequencies.