Background and aims: Nowadays, artificial insulators such as fiberglass
and rock wool are used as sound absorbers in developing countries. The present
study is performed to introduce new sound absorbing materials used in developed
countries and discuss their acoustical characteristics. It also aims to look at
the efficiency of sound absorber natural materials (green materials) as an alternative
to commercial materials with a synthetic base used in different places.
Methods: In order to identify new porous absorbents, their mechanism of action
and various applications, a search was conducted by using keywords such as
“Sound Absorbent”, “Natural Noise Absorbent” and “Passive Absorber” in PubMed,
Scopus, Science Direct, ProQuest, Springer, Web of Knowledge, Magiran, SID,
IranMedex and Google Scholar. We selected 48 review and original research
papers that were about natural and recycled absorbents. Results: Most recent
research includes production and optimization of sound absorbers using natural
and recycled materials. The aim of all of these researches was producing green
absorber materials in accordance with environmental regulations. In order to
properly use these materials, in addition to knowing the benefits and suitability
of absorbers for use in the intended environment, the effective factors in
sound absorption such as fiber size, air flow resistance, porosity, curve,
thickness and density of absorbers were considered. Conclusion: In comparison
to old absorbents, new materials are safer and lighter and enjoy a more efficient
technology. It seems like environmental friendly, degradable, recyclable and
green noise absorbents will play on important role in the market of noise
absorbents in the future. Also because of the place and different uses of
absorbent materials, specialists should consider the limitations of the
environment and the acoustic characteristics of the absorbents.