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Wednesday, July 10 • 18:10 - 18:30

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A thin nanofibrous layer used as a membrane can vibrate at low frequencies due to small interfibrous spaces and planar arrangement that are forced by low-frequency sound waves. Nanofibrous layers of very small thickness having three different surface area densities were manufactured from a polymer solution of PVA using the electrospinning method. Due to resonance at its natural frequency, the membrane is able to absorb sound energy. These unique properties come from the nature of nanofibrous webs, small fibrous diameter, the high surface area of the layer, its inner structure, and inter-fibrous spaces causing high viscous losses inside the material. Optimal rigidity and placement of the membrane facilitate its vibration. Under certain humidity conditions, visible changes in PVA fibrous structure occur, as PVA accumulates fluid in its polymer chains. Thus, the PVA membrane structure (porosity) was controlled in the range of limit values by using different vapor application time. A standard two-microphone impedance measurement tube was employed to measure the sound absorption coefficient of the nanofibrous membranes. Structural properties have been investigated with pore-size assessment, supported by air permeability and airflow resistivity measurements, all covered by Scanning Electron Microscopy. Effects of these parameters on the sound energy dissipation were compared with the sound absorption results and are discussed in this article. It has been observed that the value of membrane's porosity and resistance to airflow affect its dampening capacities, recognizing that there are additional mechanisms beyond sound absorption of nanofibrous membranes that must be investigated, thus indicating the important role of membrane nanofibrous structure in sound absorption.

Wednesday July 10, 2019 18:10 - 18:30 EDT
St-Laurent 5