Sound-Absorption Coefficient of Bark-Based Insulation Panels

Abstract

The objective of this study was to investigate the sound absorption coefficient of bark-based insulation panels made of softwood barks Spruce (Picea abies (L.) H. Karst.) and Larch (Larix decidua Mill.) by means of impedance tube, with a frequency range between 125 and 4000 Hz. The highest efficiency of sound absorption was recorded for spruce bark-based insulation boards bonded with urea-formaldehyde resin, at a level of 1000 and 2000 Hz. The potential of noise reduction of larch bark-based panels glued with tannin-based adhesive covers the same frequency interval. The experimental results show that softwood bark, an underrated material, can substitute expensive materials that involve more grey energy in sound insulation applications. Compared with wood-based composites, the engineered spruce bark (with coarse-grained and fine-grained particles) can absorb the sound even better than MDF, particleboard or OSB. Therefore, the sound absorption coefficient values strengthen the application of insulation panels based on tree bark as structural elements for the noise reduction in residential buildings, and concurrently they open the new ways for a deeper research in this field.

Keywords: biomass; impedance tube; sound absorption coefficient; spruce and larch bark; up-cycling.

Figure 1

Larch bark particles (8–13 mm) (left) and bark based composite specimens (right) for acoustic measurements.

Figure 2

Sound absorption coefficient for spruce and larch bark insulation boards, measured without wall clearance.

Figure 3

Sound absorption coefficient for spruce and larch bark insulation boards, measured with wall clearance.

Figure 4

Dependence of the sound absorption coefficient on frequency for wood-based composites with a thickness 7.9 < x < 11 mm (after Smardzewski et al. [9]).

Figure 5

Dependence of the sound absorption coefficient on frequency for wood-based composites with a thickness 16 < x < 18.4 mm and a density 500 < y < 600 kg/m³ (after Smardzewski et al. [9]).

Figure 6

Dependence of the sound absorption coefficient on frequency for wood-based composites with a thickness 22.3 < x < 28 mm and a density 220 < y < 500 kg/m³ (after Smardzewski et al. [9]).