Recycled and natural fibres: the perfect allies against noise

Acoustic materials made from recycled and natural fibres can retain much of their performance even after more than 16 years of ageing. This is the conclusion of a study led by researchers at the Gandia Campus of the Universitat Politècnica de València (UPV), whose results reinforce the potential of these materials as an alternative for more sustainable construction.

The study, published in Case Studies in Construction Materials, was carried out by Jesús Alba, Romina del Rey and Jordi Garcia-Peris, and analyses the long-term behaviour of 32 acoustic materials made from recycled polyester, textile waste, cotton, wool, hemp, jute, kenaf and coconut fibre, amongst others.

These materials are used to reduce reverberation and improve acoustic comfort in classrooms, offices, auditoriums, and homes, and can also enhance sound insulation. Although previous studies had shown that they could achieve performance comparable to conventional products, there was hardly any data on their behaviour over long periods.

Over 16 years of natural ageing

The samples analysed were originally manufactured and characterised in 2009 as part of a European LIFE project. Since then, they have been stored for approximately 16.5 years under uncontrolled indoor environmental conditions, subject to temperature and humidity fluctuations and dust accumulation.

During this period, the samples were exposed to temperatures ranging from approximately 0 °C to 35 °C and relative humidity levels between 45% and 85%. These conditions made it possible to study their response to prolonged ageing, similar to that experienced by many acoustic materials used in indoor spaces.

The team re-analysed the samples using the same procedures employed in 2009 and compared key parameters such as sound absorption and air-flow resistance.

"The results show that, in general, the materials retain a large proportion of their original acoustic properties after more than a decade and a half," notes Jesús Alba.

The study found greater stability in predominantly synthetic materials. Those made from natural fibres or hybrid combinations showed greater sensitivity to ageing, while also retaining remarkable acoustic performance. Overall, the results confirm that both recycled and natural materials can maintain adequate sound absorption capacity over long periods.

The researchers supplemented the study with optical microscopy analyses to assess possible changes in the structure of the fibres, their diameter and porosity, and better understand the physical transformations associated with natural ageing.

According to the UPV team, these results provide useful data for architects, engineering professionals and manufacturers, and help to reduce uncertainty regarding the durability of recycled and natural materials used for the acoustic treatment of buildings.

Reference

Jesús Alba, Romina del Rey, Jordi Garcia-Peris. Durability of recycled and natural fibrous acoustic materials undergoing long-term indoor ageing. Case Studies in Construction Materials, 25 (2026), e06339.