*3.3. Prototyping Process*

We have created an Android mobile application as a tool to deliver the proposed sound code to users. Figure 5 shows the prototyping process for creating a mobile application used as a tool for expressing color using the proposed sound code.

**Figure 5.** Prototyping process.

The first step was to analyze the images of the whole work. The specific method was to use software such as Photoshop to divide the artwork into specific grids (e.g., 15 × 19 or 12 × 15) and analyze the name, color, and depth of each object along with the artwork introduction. The analysis selected a specific name, color and brightness level, and depth level. The second step was to create an audio file corresponding to the spoken instructions with names for all analyzed objects. The third step was to apply HRTF to each part of the audio file corresponding to the object name to represent the object's color in 3D sound. The fourth step was to use Adobe Audition audio processing software to perform pitch scaling without time scaling processing and reverberation processing on each part's voicedescribed audio file through the lightness of the color and depth levels. The fifth step was to create a mobile application using Android Studio software. The basic making method was to split artworks as buttons in the way described above and add processed audio files to each part. The artworks used in this prototype as examples were John Everett Millais' "The Blind Girl" and Gustave Caillebotte's "The Orange Trees." The prototype application interface is shown in Figure 6. Figure 6a,b shows where the user could apply the 3D sound coding to the artwork for viewing. By clicking on any part of the artwork, the user could access the audio description of the clicked area. Additionally, each voice description used sound coding in this paper. It was possible to obtain information about color, brightness, and depth while receiving the voice description. Figure 6c shows the listening test of the application. The user could perform headphone tests and sound learning in this interface.

**Figure 6.** Application interface. (**a**) The Blind Girl interface; (**b**) The Orange Trees interface; (**c**) test interface.

### **4. User Test and Results**
