## 1 Introduction  
In South Korea, the most common complaint from residents in multi-unit housing is floor impact noise from units upstairs and downstairs [1, 2]. To address this acoustic problem, various stakeholders, including the government, construction companies, research institutions, and universities, are developing a range of technologies [3, 4, 5, 6]. The products and solutions resulting from these research and development efforts are being applied to newly constructed multi-unit housing [7, 8, 9]. Furthermore, construction companies use these technological developments as a promotional tool [10, 11, 12]. The most active technology developed to solve the problem of floor impact noise is the development of floor structures [13, 14]. Currently, developments include hollow slabs and techniques to increase the thickness and rigidity of the slab beyond the 210 mm bare slab [15; 16; 17]. The main development is the installation of resilient structures on top of the bare slab [18]. This involves installing a bare slab, resilient material, light-weight concrete, and a finishing mortar structure. However, there have been recent technological advancements that allow for the thickness and strength of the finishing mortar to be increased, resulting in a single structure of finishing mortar [12]. This type of floor structure is currently being used in multi-unit housing. The materials used for the resilient layer of the floating floor structure have evolved from single structures, such as EPS (Expandable Polystyrene) and EVA (ethylene-vinyl acetate), to composite structures that combine EPS, EVA, and other materials [7; 12; 19; 20]. Additionally, cushioning materials are being developed using a wider range of materials beyond EPS and EVA, and various structures, not just flat types, are being applied for their development [12]. The progress of developing ceiling structures in receiving rooms to reduce noise from floor impacts is also underway [21; 22; 23; 24; 25; 26]. This involves using internal acoustic materials to minimize the amplification of impact noises to the room below due to the influence of the air layer within the ceiling and a ceiling-less design to minimize the transmission of impact noises through the ceiling. Furthermore, there have been notable design alterations aimed at minimizing floor impact noises, such as changes in the placement of load-bearing walls and advancements in floor design to manage sound patterns [25]. However, the application of such research and technology appears to be passive and insufficient from the perspective of apartment dwellers [27; 28]. Residents of apartments, especially those with young children, are particularly sensitive to the problem of floor impact noise. To address this issue, the most effective solution is to install floor mats of a specific thickness [29; 30; 31; 32]. It has been shown that floor mats are typically installed in living rooms and playrooms, and they usually have a minimum thickness of 10 mm and a maximum thickness of 50 mm [33]. Furthermore, the primary outcomes of some studies consist of the outcomes of a survey that asked apartment residents about the measures they take to prevent floor impact noise and the preemptive actions they take [34]. The most frequent response was 'educating children', followed by 'using floor mats or carpets', and thirdly 'wearing slippers'. In addition, the government has declared its intention to support apartment residents in purchasing floor mats to reduce floor impact noise by making such purchases interest-free [35]. Thus, apartment residents invest in floor mats to reduce inter-floor noise. However, there is an issue characterized by residents not receiving the expected impact sound reduction performance from the floor mats despite their financial investments. The Korean standard KS F 2865 provides a method for measuring and evaluating the impact sound reduction performance of floor surface finishing materials and floor mats in South Korea [36].