## 1 Introduction  
In Korea, more than 65% of the population lives in apartment houses, which means the probability of exposure to floor impact noise is very high. In fact, complaints about floor impact noise collected from 16 cities and provinces are steadily increasing [1]. According to a survey by the Ministry of Environment, 76.2% of respondents indicated that the major source of noise came from upper-story apartments, highlighting the seriousness of the floor impact noise issue. Statistics from the \"Neighbors Center\", operated by the Ministry of Environment of the Republic of Korea, show a steady annual increase in consultations received through call centers and websites. The severity of floor impact noise is evident from the sharp increase in telephone consultations, which rose from 8795 in 2012 to 28,231 in 2018 [2]. A survey conducted on households affected by floor impact noise found that heavy-weight impact noise accounts for more than 90% of the reported noise, indicating an urgent need for a solution to this problem [1]. Since 2003, the Korean government has enacted and reformed laws to reduce floor impact noise in apartments. To more precisely measure the noise experienced by residents, the noise produced by running children, which is regarded as the most serious noise source,was analyzed [3]. Additionally, the measurement results under various conditions were compared with the noise generated by an impact ball [4]. A similarity in noise transmission was found between the impact ball and running children, which is why the impact ball is currently used as a standard heavy-weight impact source along with tapping and bang machines [5]. [PERSON] undertook floor impact noise tests using 19 different resilient materials, including EVA, PET, PP, and PS sheets. The results showed that a maximum reduction of 5 dB in heavy-weight floor impact noise could be achieved compared to a bare concrete slab [6]. Similarly, [PERSON] measured the dynamic elastic modulus of nine specimens, comprising EVA, EPS, PE, crumb rubber, and glass fiber materials. He found that the dynamic elastic modulus decreases with increasing thickness of the composite materials, regardless of the type of resilient material used [7]. Another similar experiment used 20 mm of EVA resilient material with a concrete slab of 180 mm thickness, resulting in a 2 dB reduction in heavy-weight floor impact noise [8]. The management regulations for the \"certified slab structure\", a floor structure system suitable for reducing floor impact noise, were established in 2000 [9]. However, the actual floor impact noise reduction effect was insignificant. To address these issues, the Ministry of Land, Infrastructure and Transport of the Republic of Korea has operated a \"pre-certification system\" since 2005 to control floor impact noise in newly built apartments. The pre-certification system involves certifying the floor impact noise insulation performance of apartment floors in a laboratory setting. However, due to discrepancies between laboratory measurement results and actual performance, it was difficult to achieve realistic floor impact noise reductions. For this reason, the Korean government is currently implementing a \"post-certification system\", which evaluates the floor impact noise insulation performance after construction [10]. Numerous surveys and polls have revealed that residents in apartments experience significant stress due to floor impact noise. Although material developments have been conducted to reduce floor impact noise, these efforts have not efficiently mitigated both light- and heavy-weight impact noise simultaneously, highlighting limitations in materials and technology. It was also found that noise buffering on floor surfaces, including flexible floor finishes, effectively reduces only light-weight floor impact noise, with minimal impact on heavy-weight noise. This limitation has led to expanded research into ceiling-slab configurations, aimed at reducing low-frequency impact sound [11].