Work

Sound absorption of foam-formed bean hull and birch fibres

Year: 2026

Type: article

Abstract: The reduction of sound pollution within buildings is vital in today’s noisy environment. In this study, faba bean ( Vicia faba ) hulls were successfully soda pulped for the first time and manufactured into environmentally friendly sound-absorbing foams. The foams were produced by foam forming the faba bean hull fibres (BH) with bleached birch Kraft pulp fibres using sodium dodecyl sulphate. The hardwood fibres (HW) backbone was strengthened by the short BH fibres (123 μ m) as the compression test shows higher resistance by adding 3 g (oven dry) BH fibres to the hardwood foam (5 g o.d.) compared to a foam consisting only of HW fibres. With increasing BH fibre amount the compressive strength increases further alongside the foams drying time, bulk density and flow resistivity. Photographs, micrographs, and X-ray tomographs revealed a highly heterogeneous foam structure with a pore size distribution between 60 and 480 μ m. Impedance tube measurements demonstrated that the BH-HW foams have a sound absorption coefficient of 0.50 at mid-low frequency 650 Hz with the highest absorption coefficient of 0.98 at about 1200 Hz. After the compression test, the foams showed a slightly decrease in absorption coefficient. Overall, the increased BH fibre content shifted the absorption curve to lower frequencies. We demonstrate that underutilized materials like faba bean hulls from the food industry can be pulped and valorized for the application of acoustic absorber.

Source: Bioresource Technology Reports

DOI: 10.1016/j.biteb.2026.103055

Authors: Marike Langhans, Tuomas Hänninen, Arif Onur Yürek, Jose Cucharero Moya, Tapio Lokki, Jaana Vapaavuori

Institution: Aalto University

Language: English

Topic: Natural Fiber Reinforced Composites

Subfield: Polymers and Plastics

Field: Materials Science

Domain: Physical Sciences

SDG: Responsible consumption and production

Open Access status: hybrid

Estimated APC paid: $3,920