# Improving Engineering Design Using Smart Evaluation of Indoor Acoustical Climate of Dining Places
## 1 Introduction  
Interior acoustics involves designing acoustic conditions that are adequate for music or speech perception in rooms. The relevant criteria for the acoustic climate, which can be divided into subjective and objective criteria, are related to the intended use of the rooms. Subjective criteria are based on the audience's opinion and are used to evaluate a room's acoustic characteristics. Many researchers have endeavoured to discover the relationship between the subjective and objective evaluations of acoustic characteristics to link subjective opinions with interior acoustic design methods [1, 2]. The objective evaluation criteria are based on acoustic measurements and are of great significance for the entire design process. These criteria include those that are based on model studies, computer simulations, and measurements at different implementation stages (design interim checks), but are uncontrollable at the design stage, and can be inspected only in a completed building structure [3, 4, 5]. The interior acoustic climate indicators are significantly affected by the following factors: interior geometrical proportions, sound-scattering and -absorbing elements, the arrangement of mobile and fixed rooms in the interior, and the existence of a sound system in the interior [2, 6]. Interior acoustic parameters are best evaluated through speech comprehensibility tests (using appropriate methods). A dining place's acoustic climate includes adequate acoustic conditions that are indispensable for speech perception in the interior. Another issue of interest is the quality of acoustic parameters such as the reverberation time or sound level, depending on the interior design, density of people in the room, or furnishings. This is encompassed by the concept of an acoustic climate [7; 8; 9]. An interior acoustics designer or architect focuses on the parameters used at the design stage. Considering the primary functions of dining places, such as meetings with discussions or ordering food, the reverberation time seems to be the main criterion for interior acoustic evaluation, especially from the designer's perspective [2; 8; 10]. This can be determined as early as the design stage. In addition, the reverberation time is used to calculate other acoustic parameters, such as the Speech Transmission Index (STI). The STI parameter values ranged from 0 to 1 and were well correlated with the quality of speech intelligibility in the enclosure. The STI is based on the transmission of modulated sound, where the spectrum imitates the human voice. Building design is a multiplex process that encompasses several operations. To provide adequate quality in an enclosed climate, many attempts have been made to streamline the design. Quality control mechanisms are required during construction. Many recent developments intended to ensure high efficiency and quality are employed in the design stage because the process lacks evaluation procedures. Designing as a process is performed in a traditional, linear way, which lacks essential analysis steps, such as design evaluation or optimisation. Currently, many optimisation methods are related to cost and construction reductions, energy efficiency, or floor plan configuration [11]. Multiple criteria decision making should be an important part of the design process. This article presents an easy-to-use, index-based method for non-acoustician architects and designers. The novelty of the method is that it can be implemented during architectural arrangements to assess the indoor quality of dining places in the early design stage. In the literature, several quality index methods have been proposed [12; 13; 14], but most of them are based on measured data or data obtained by computer simulations. The main goal of the method proposed in this study is to provide architects and designers with simple tips for creating an enclosure with a proper acoustical atmosphere.