## 1 Introduction
This standard defines a method for measuring the level of reduction in light-weight and heavy impact sounds achieved by floor surface finishing materials, excluding floating floor layers constructed on a concrete slab in a laboratory. The method is applicable to both single-layer and multi-layer floor finishing materials installed on a standard concrete floor. The scope of the test floor is defined as 'a reinforced concrete flat plate with a rectangular planform and a thickness of 120 mm to 210 mm'. Some floor mat manufacturers and developers only present the impact sound reduction performance of light-weight impact sound, which is generally high, through the Korean standard code. The evaluation does not include the impact sound reduction performances of a bang machine and rubber ball, which are heavy-weight impact sounds with relatively low impact sound reduction performance. Heavy-weight impact sound is created by simulating the behavior of children in apartment houses, which differs from the purpose of applying floor mats in apartment houses. The impact sound mentioned in the current Korean standard code is different from the impact source generated by children's behavior. Therefore, even if floor mats are applied, the impact sound reduction performance caused by banging machines and rubber balls is insignificant. Additionally, the impact sound reduction performance of floor mats varies depending on the accuracy of information such as the thickness of the floor structure, as mentioned in the Korean standard code. On the other hand, the basic application guidelines for evaluating the performance of floor covering products are provided in Annex H of the International Standard ISO 10140-1 [37]. The improvement of impact sound insulation by a floor covering is calculated as the difference between the impact sound pressure levels before and after the installation of the floor covering. The ISO 10140-3 standard specifies the details of the measurement of the impact sound pressure level, and the ISO 10140-5 Annex C specifies the reference floors on which the floor covering is installed [38; 39]. ISO 10140-5 Annex C defines one heavy-weight reference floor and three types of light-weight reference floors. The heavy-weight reference floor is a reinforced concrete slab with a thickness ranging from 100 mm to 160 mm. This contrasts with the heavy-weight reference floor in KS F 2865, which requires a minimum thickness of 120 mm to 210 mm and is intended for slabs with a thinner thickness range. The reason for this difference is that floor impact noise has become a significant social issue in South Korea, and the law mandates heavier and more rigid structures to address it. Although reinforced concrete slabs as thin as 100 mm are structurally safe, South Korea currently mandates a minimum slab thickness of 210 mm or more to reduce heavy impact noise caused by children walking around barefoot. A statistical trend toward a reduction in heavy-weight impact sound was observed after the enforcement of legal regulations requiring increased slab thicknesses [3; 40]. Additionally, the introduction of high-tight windows has reduced background noise. Furthermore, an increase in complaints about inter-floor noise suggests a need for further enhancements in the performances of floor coverings [32; 41; 42]. This study evaluated the reductions in light-weight and heavy-weight impact sound achieved by various flooring mat materials at four different test-beds with a thickness range of 150 mm to 210 mm, as specified in KS F 2865. The evaluation method used was like the impact sound generated by children's activities in previous studies. The reduction performance was evaluated by frequency bands and as a single-number quantity. Furthermore, a correlation analysis was carried out on floor structures of various bare slab thicknesses to provide fundamental data on the reliability of the evaluation method, focusing on the sound reduction performance of the same floor mat.