A Method for Predicting L' nT,w for Lightweight Floating Floors Comprising Low Density Flexible Polyurethane Foam on Concrete Supporting Floors

Abstract

Lightweight floating floors of medium density fibreboard supported by a resilient layer of flexible polyurethane foam are increasingly being used in both new build and refurbishment projects. BS EN 29052–1 describes the Standard Method for determining the dynamic stiffness of resilient layers used under floating floors: this states that the Standard does not apply for loadings of less than 0.4 kPa, which is higher than the static load imposed by medium density fibreboard. The Standard also states that it does not apply to materials whose airflow resistivity is less than 10 kPa.s/m² if the dynamic stiffness of the air enclosed in the material is not negligible compared with the apparent dynamic stiffness of the test specimen. Despite these restrictions it was found that, when sections of flooring were tested in the field, the Standard Method provided data which allowed the prediction of the improvement in impact sound insulation over a range of 40 dB and also the prediction of the weighted standardised impact noise level according to BS 5821. 1984. Part 2. This was achieved by taking account of the stiffness of the air in laboratory samples and the effect of the mass impedance of the hammers on the standard tapping machine used in field tests.

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