**3. Acoustical interior design elements**

Interior acoustics support the well-being of the users. The design of the spaces that require a sound quality needs specific elements to embolden the acoustical quality. The interior acoustical elements involve and interlace with other acoustical fields. These elements start by the space layout, which should be architecturally created to the specific function to prevent any basic problems. Otherwise, the interior solutions could cover such deficiency. The selective materials are the essence of the interior acoustical design. The interior treatments, quality, and position play the main role in the excellence of the acoustical functionality. It is a pure interior design, although the architect and especially the architectural acoustician consider it, to a very recent date, architectural treatments. The acoustical sound systems come as the third element as it is the additional element to any acoustical interior, for specific targets. If the acoustical interior design reflects the user's function, the acoustical engineering solutions presented through the sound systems should have a specific objective.

The sound design, as a background, affects the users unconsciously. It could contribute to the psychological mood of the users. Human is productive while listening to his/her favorite music by 30%. The type of sound background—or

the soundscape—contributes in the overall success of the interior functions. Slow music accelerates the blood circulation, therefore speeding up human functionality. On the other hand, the slow music depresses most of the time the human being. Soundscape, as a new psychological tool, bolsters in today interior design upgrading the overall interior purposes.

The interior acoustical design is a combination of these three important elements that create the interior spaces in excellence [7].

## **3.1 Interior acoustical layout**

The architectural design affects deeply in the interior sound behavior. While the sound behavior follows the architectural layout, the architectural shape could lead to a successful acoustic or a harmful one. The architecture should support the acoustical design to enhance the functionality rather than create problems that need extra solutions. Domes, circular plan, parallel surfaces, and unproportioned spaces lead to several acoustical problems for the interior spaces. Solving these problems will over cost the interior, as the acoustical treatments are expensive as raw materials and as fire-resistant coatings [8].
