# Improving Engineering Design Using Smart Evaluation of Indoor Acoustical Climate of Dining Places
## 4 Acoustical Analysis of Dining Places
This location of the sound source reflects that of loudspeakers emitting music in a restaurant or a loudspeaker for an audio alarm system in restaurants located, for example, in shopping malls. The sound absorption coefficient is a measure of the amount of sound energy removed from the wave that hits the material. This parameter indicates the ability of a material to absorb sound energy. Sound absorption can be described as a single number, \(\alpha_{\text{w}}\), the weighted sound absorption coefficient, in the range from 0 to 1. It was measured according to ISO 354 and calculated according to ISO 11654 [57; 58]. Based on the findings of [PERSON] and [PERSON], the absorbing material was placed on the ceiling [47]. The analyses revealed a significant influence of sound-absorbing materials on the indoor acoustic climate of dining venues. However, the literature shows that the arrangement of various absorbers has no significant influence. In flat and long dining halls, it is essential to place the absorbers strategically [9]. According to the literature, the volume of a restaurant room plays a key role and should be as high as possible. The height of the eating establishment plays a crucial role \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Surface**} & \multirow{2}{*}{**Material**} & \multicolumn{6}{c}{**Absorption Coefficient \(\alpha_{\text{p}}\)**} \\ \cline{3-8}  & & **125 Hz** & **250 Hz** & **500 Hz** & **1000 Hz** & **2000 Hz** & **4000 Hz** \\ \hline Floor & Linoleum & 0.02 & 0.02 & 0.03 & 0.04 & 0.04 & 0.05 \\ \hline Walls & Painted smooth concrete & 0.01 & 0.01 & 0.02 & 0.02 & 0.02 & 0.05 \\ \hline Chairs & Thin plywood & 0.42 & 0.21 & 0.10 & 0.08 & 0.06 & 0.06 \\ \hline Tables & Glazed tiles & 0.01 & 0.01 & 0.01 & 0.01 & 0.02 & 0.02 \\ \hline Ceiling & \multicolumn{6}{c}{Different values for different calculations in the range of \(\alpha_{\text{p}}\) 0.1–0.4–0.8} \\ \hline \end{tabular}
\end{table} 
Table 1: Coefficients of sound absorption for materials used in the dining place model. Figure 2: View of the simulated enclosure. in its volume [2; 41]. If the owner requires a specific reverberation time, the architect can design an optimal height in connection with the density factor. An essential element considered in many publications is the issue of the acoustic capacity of a dining room, as the maximum number of people for which sufficient communication quality between people is ensured. This value was calculated using the following formula:  
\[\text{N}_{\text{max}}=\text{V}/20\,\text{T}, \tag{1}\]  
where V is the volume of the enclosure [m\({}^{3}\)], and T is the reverberation time [s]. [PERSON] provided requirements as a function of the number of people relative to the acoustic capacity of the room [42]: up to 0.25 is assessed as a good ambient noise level, 0.25 to 1 is satisfactory and sufficient, and over 1 ambient noise level is insufficient and very bad [36]. The influence of the ceiling sound absorption and capacity, given as the number of tables (9-25-42) with seats in a room, on the STI index is presented in Figure 3 (simulated at 1.2 m above the ground). It was shown that the capacity, by adding absorption and sound dispersion, increased the STI values. Thus, it increases the acoustical quality of the dining enclosure. Previous results have shown that to improve or achieve acceptable verbal communication quality, it is recommended to place any kind of boundary or barrier around tables and chairs. To control the reverberation time, it might not be adequate to simply increase the room's surface absorption or reduce the ceiling height. However, increasing the absorption coefficient of the surfaces and placing boundaries around the tables can provide optimal communication conditions. For dining places, where these treatments (sound-absorbing materials and barriers) can be expensive, reducing the room volume by splitting it into smaller spaces (with sound-absorbing walls) is a cost-effective way to improve the acoustic conditions [30].