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A simplified measurement method for the determination of impact sound reduction Marc Sommerfeld Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany, marc.p.sommerfeld@ptb.de Introduction Impact sound reduction is the main quantity for describing the acoustic behaviour of floor coverings. Its determination is standardised in ISO 140-8 [4] and ISO 140-11 [5] and requires the use of a special test facility. This facility consists of two rooms of about 50 m3 each, separated by a 16 cm concrete slab or a special timber joist floor. Manufacturers of floor coverings see the advantage of having their own test facilities but the investment often cannot be afforded by the small- and medium-sized enterprises. Therefore, a research project was started with the aim to reduce the effort for the determination of the impact sound reduction. The project is funded by the German Federation of Industrial Research Associations "Otto von Guericke" Inc. (AiF) and has a duration of 2.5 years. The research work is carried out at PhysikalischTechnische Bundesanstalt (PTB) and at the Research Institute of Leather and Plastic Sheeting gGmbH (FiLK). Existing short test method The starting point of the investigation is a known short test method TGL [1], [2]. The maximum acceleration of a 500g hammer is measured when it falls from a height of 4 cm on a soft layer. From the maximum acceleration, the rated value of the reduction of transmitted impact noise is calculated directly. derived (for the reduction of transmitted impact noise) turned out to be essential. Moreover, a typical value of the size of the impulse is used which was determined from measurements [1] with floor coverings available at that time. An adaptation to today's layers would not lead to the goal, because the measuring procedure would not be applicable without necessary adjustments at regular intervals in comparison to the floor coverings currently placed on the market. A project task is the elaboration of a procedure which can be introduced as a work item proposal at ISO. This aim is not accessible by the (perpetual) modification of the TGL standard. New compact measurement set-up - COMET Within the scope, a compact measurement set-up is developed which delivers rated values [6] of the reduction of transmitted impact noise. The results should correspond on average to those of the ISO procedure ISO 140-8 [4] and respectively, ISO 140-11 [5], and the realisation of the measurement should be easy. In the constructional systems, two floors should be used by analogy with the ISO procedure: a heavyweight floor and a lightweight floor. The required applicability is the operation with soft floor coverings. Parquet or laminate is to be examined. The first construction consists of a concrete slab of the dimension 1.2 m x 0.8 m x 0.2 m which lies in a steel rack in the Euro format. Between stilts and concrete slab, an elastic material is introduced which decouples the concrete slab. The system resonance lies at f = 27 Hz and therefore below the interesting frequency range of building acoustics (see figure 2). Figure 1: Difference of ∆LW [dB], concrete: TGL [2] vs. ISO procedure [4] Initially it was examined as to whether this procedure, perhaps with small adaptations, could also be applied today. In an AiF pre-project [3] it appeared that the results of the TGL procedure are systematically about 3 dB smaller than those of the ISO procedure (see figure 1). Based on this situation, the TGL procedure was analysed. The assumption of an impulseshape from which a general spectrum was Figure 2: Construction of COMET, concrete floor The second construction consists of a timber joist floor of the dimension 1.2 m x 0.8 m x 0.2 m which lies in a steel rack in the Euro format (see figure 3). Between stilts and

concrete slab, an elastic material is introduced which decouples the timber floor with a resonance at f = 22 Hz. It is thus below the interesting frequency range of building acoustics. The construction is related to the timber joist floor (type 1) described in ISO 140-11. The only difference in dimension is the distance between the two timber joists: instead of 62.5 cm they have a gap of 68 cm. The measurements are carried out with a 1/3 octave band analyser. For the excitation, an ISO tapping machine is used. In analogy to the ISO procedures, two tests are performed, once with and once...

They reach values of up to 4.4 dB. The discrepancies are to be investigated in future. There is no systematic deviation visible between the results. The mean squared deviation turns out to be 1.9 dB. It is thus larger than that for the concrete slab. The reason is the more complex transfer of vibrational energy to the measuring points due to the inhomogeneous receiving structure. PVC carpet laminate linoleum ∆L COMET PVC L ∆L ISO 140-11 PVC L L ∆L COMET carpet L ∆L ISO 140-11 carpet Figure 6: Deviation of ∆Lw [dB], concrete: COMET vs. ISO procedure Table 1 shows the maximum deviation ∆max....

40 PVC carpet laminate linoleum The author expresses his gratitude to AiF for funding the project and to the manufacturers of floor coverings who supplied numerous test specimens. The contribution of FiLK, especially in establishing the contact to AiF and to industry, is gratefully acknowledged. I furthermore thank Prof. Dr.-Ing. Werner Scholl and Dr.-Ing. Volker Wittstock for initiating the project and for their enduring support. Many thanks go to Dipl.-Ing. Sylvia Stange-Kölling for doing numerous measurements. Figure 9: Deviation of ∆Lw [dB], timber: COMET vs. ISO procedure Figure 11:...