# Cross-Laminated Timber Floor: Analysis of the Acoustic Properties and Radiation Efficiency
## 1 Introduction  
Cross-Laminated Timber (CLT) has increasingly become a timber product of global interest [1]. On the one hand, this is due to (i) the many merits of eco-sustainable wooden building elements, characterized by wide availability in nature, (ii) relative ease of handling and (iii) its environmental friendliness and wide range of end uses [2]. On the other hand, CLT is well known for its suitability [3] in the construction sector and its structural behavior [4]. However, due to their lightweight characteristics, CLT structures are characterized by poor acoustic performance [5]. Many studies were developed to determine if timber component properties are well known among users and the scientific community. The results demonstrate that there is no agreement on this topic [6]. For these reasons, there have been several recent experimental studies to determine the acoustic performance of CLT, with particular attention to its impact on noise behavior [7], and also for comfort perspective on users [8]. For example, [PERSON] et al. [9] published the results of a comprehensive experimental study on the sound reduction index of CLT wall and floor systems, and also presented a method usable for calculating the flanking sound transmission, based on the vibrations measurement of sound reduction index, related to different types of panel joints. [PERSON] et al. [10] carried out measurements aimed at quantifying the impact noise of CLT floors, the airborne sound transmission and the lateral transmission, through joints between CLT panels, which were used as a starting database to assess the acoustic performance of a large building structure. [PERSON] et al. [11] collected the results of laboratory measurements on the impact insulation of various CLT floor constructions. Other studies on the impact insulation of different CLT floor systems are presented by [PERSON] et al. [12], [PERSON] et al. [13] and [PERSON] et al. [14, 15, 16]. [PERSON] et al. [17] presented the results of an experimental campaign on flanking sound transmission. In this perspective, further studies are needed to develop and improve prediction models of CLT floor sound and vibrational behavior [18; 19]. In this regard, the sound radiation index is of paramount importance to understand and simulate the behavior of these elements [20; 21]. Hence, to design CLT structures with good acoustic insulation, there is a need to characterize the sound radiation of the vibrating elements. Acoustic radiation has generated increasing interest over the past decades and it has been used in acoustic calculation models, for example, ISO 12354-1 [22]. Thus, to obtain a complete vibro-acoustic characterization and, in particular, to fully understand how material properties impact on the acoustic performance of structural elements, and meet the high quality standards required for CLT floors [23], the sound radiation of CLT floor is an issue that needs to be deepened and studied. [PERSON] and [PERSON], in 1994 [24], presented an extensive and detailed bibliographic analysis of the prediction models to compute sound radiation in the same decade, while [PERSON] et al. [25] proposed a generalized model for the acoustic radiation from baffled and unbaffled homogeneous plates, with arbitrary boundary conditions. A similar approach was also used by [PERSON] et al. [26] and by [PERSON] et al. [27; 28], to develop a tool to predict the acoustic and structural vibration response of sandwich plates. More recently, [PERSON] and [PERSON] [29] presented a semi-analytical model to investigate, numerically, the vibro-acoustic response of stiffened plates, while [PERSON] et al. [30] analyzed orthogonally ribbed plates by means of a periodic theory. [PERSON] and [PERSON] [31] used statistical energy analysis and the transfer matrix method to estimate the vibro-acoustic response of mechanically excited multilayer structures. Considering these studies as a reference, analyses on the vibro-acoustic behavior and radiation efficiency of wooden elements have recently been developed [32].