On acoustical properties of novel foam-formed cellulose-based material

Novel biodegradable, low-density porous materials based on wood fibres are produced in foam-laid media called foam-paper. The effects of various parameters - such as foam air-content, thickness, porosity and consistency of the foam-fibre solution-on the acoustical properties of the final products using an experimental setup based on three-microphone impedance tube are investigated. Freeze-dried foam-formed paper (foam-paper) using nanofibrillated fibres are made to study the effect of tortuosity and crowding number on the normal sound absorption coefficient. The results show that the acoustical properties of foam-formed materials using nanofibrillated fibres are much greater than the standard NBSK foam-papers. To improve the acoustical properties of standard NBSK foam-papers, the sound absorptions of compressed multi-layer foam-papers are tested. The results show that the sound absorption of compressed three-layer NBSK foam-paper is more than three times greater than a single layer NBSK foam-paper at a frequency of 1000 Hz.