The use of agglomerated cork as an underlay for improvement of impact sound insulation in buildings

The cork‐oak is only abundant in the Western part of the Mediterranean and is an important feature of Portuguese landscape and heritage. Portugal has about 30% of the world’s cork‐oak trees and accounts for more than half of the world’s cork production. Agglomerated cork has natural cork granules (the by‐products from the production of other cork products) as its base material. The project goal was to test and characterize the use of agglomerated cork as underlay to increase the impact sound insulation. Eight different cork agglomerate products were tested to assess their impact sound insulation quality when used as underlays with four different floor coverings (linoleum, ceramic tile, and two types of wood parquet). The measurements were made on‐site (with flanking transmissions) on a coffered concrete floor without a fastened ceiling and according to International, Portuguese, and American standards (ISO‐140/6 and 717, NP‐669 and 2073, and ASTM‐E989 and 1007). The results show that the use of this underlay improves the weighted index (Ln, w, or IIC) for each respective reference floor up to 19 (for ceramic tiles), 20 (thin parquet), 21 (linoleum), and 26 dB (thick parquet). Prediction formulas, determined by statistical analysis, are also presented.