# City Ditty: An Inmersive Soundscape Sketchpad for Professionals of the Built Environment
## 2 Requirements Gathering, Design, and Development
### Implementation: City Ditty, An Immersive Soundscape Sketchpad  
In order to facilitate a fully immersive and interactive 3D audio-visual design environment, City Ditty was designed using the Unity game engine. The current version runs in a Desktop Virtual Reality format with monitor, headphones, keyboard, and mouse. A fully navigable 3D model of a city is included, which includes a simple user interface that allows the users to both traverse and interact with the city. An urban city centre was reproduced for this study as it provides a busy environment that can attract a lot of people, traffic on two sides of the city centre, and provides a sizeable open space for design. It was not modeled to emulate any particular location to avoid biases from comparison. The centre is divided into two green spaces with several sample scenes available, including an initial setup that includes a fountain, construction, a cafe with piano music under a pavilion, people talking, pub music at night, and an HVAC atop one of the buildings. The other green space remains empty to give the user a place to design their own space. The city centre has roads on two sides, with the side streets blocked off from cars to allow an interrupted pedestrianized section (Figure 1). Audio is rendered through Unity's built-in audio engine which produces a stereo output that simulates a 5.1 speaker setup through headphones. Due to the nature of ground-up designed soundscapes, an isolated recording of each individual sound source was introduced into the 3D virtual environment in mono. The Unity Audio Renderer relies on panning, distance attenuation based off logarithmic roll-off, and Doppler effect for moving sound sources to reproduce the spatial qualities. The individual audio files came from a variety of sources. Ambient sounds were locally recorded by our team using a first-order Ambisonic microphone (Soundfield ST350). Specific sound sources were close-micked with directional microphones and came from different sound clip archives such as freesound.org and professional sound recording engineers' libraries. Sounds were mixed (e.g., indoor pub music with voices of patrons) by a professional sound recording engineer to provide realistic sound levels of individual sound sources while ensuring that the sound level of the overall soundscape remained comfortable. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Broad User Goals** & Create a relaxing atmosphere to promote city park usage \\ \hline
**Influencing Theme(s)** & Raise sound awareness & Introduce wanted sounds \\ \hline
**Functionality** & Must be able to add objects to a city scene \\ \hline
**User-Interface Element(s)** & Add Object Menu & Placement Interface \\ \hline
**Individual Task** & Place a bird feeder in a tree to attract birds \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Tracking user goals through themes, functionalities, and relevant user interface elements to produce an informed and testable task for users to complete. Upon starting City Ditty, the user enters the sound awareness session. This places the user in the center of the city centre between the two green spaces, facing the populated side, and encourages them to explore the space while following the sound awareness tasks. During this exploration, users learn to add and manipulate different sound objects while learning more about soundscapes. Users are also introduced to different functions that help them find and visualize the different sounds together (Figure 1) and are encouraged to interact with the environment at different times of the day and season (Figure 2) to experience different contexts in the same space. Figure 1: **(Top)**: Overhead view of a blank canvas of the city centre. **(Bottom)**: The user is guided through the city centre while following instructions on how to add, move, remove, and manipulate objects. The user can optionally highlight sound sources to help visualize the sound environment. Red is for machinery, green for nature-like sounds, blue for people, and purple for music.