A compact method for the determination of impact sound reduction

The effort to determine impact sound reduction is high due to the use of a building acoustic test facility consisting of two rooms of about 50 m³ each. A compact measurement method was now developed at PTB where the complete two-room configuration is replaced by a desk-sized setup.

Impact sound reduction is the main quantity for the description of the acoustic behaviour of floor coverings. Its determination is standardised in ISO 140-8 and requires the use of a special test facility. This facility consists of two rooms of about 50 m³ each, separated by a concrete slab with a thickness of about 16 cm and a size of about 20 m². The sound pressure level in the lower room is measured when the slab is excited by a tapping machine. Two measurements are necessary, one with and one without the covering. The impact sound reduction is calculated from the sound pressure level difference according to ISO 717-2.

Manufacturers of floor coverings are interested in having their own test facilities for reasons of quality management and product development. But the effort is often inappropriate for the mostly small and medium-sized enterprises. Therefore, a joint research project was started by PTB and FILK (the Research Institute of Leather and Plastic Sheeting) which was funded by AiF, the German Federation of Industrial Research Associations. The main outcome of this project is a compact measurement setup (COMET) for the determination of impact sound reduction.

The chosen construction consists of a concrete slab with the dimension 1.2 m x 0.8 m x 0.2 m which lies on soft pads in a steel rack in the Euro format. This desk-sized setup replaces the complete two-room configuration. In analogy to the ISO procedure, an ISO tapping machine is used, and two tests are performed, once with and once without the floor covering on the slab. Instead of the sound pressure in the receiving room, the appearing oscillations are measured at the bottom surface of the concrete slab. The difference between the oscillation levels can be evaluated according to ISO 717-2. The deviations between both methods are very small for locally reacting coverings, such as PVC, carpet and linoleum (Figure 1). Laminate reveals larger discrepancies since this is not a locally reacting covering. The observed deviations are generally small in view of the uncertainties in building acoustics which often reach values of several dB. With these excellent results, the project was completed successfully. The compact setup was introduced as a new work item proposal in ISO. The first manufacturers of floor coverings have shown their interest in this method. A follow-up project is in preparation to develop a compact method for timber floorings.

Figure 1: Impact sound reductions ?L_w on the concrete slab: COMET vs. ISO procedure

Contact person:

Marc Sommerfeld, Dept 1.7, WG 1.71, marc.p.sommerfeld@ptb.de