# City Ditty: An Inmersive Soundscape Sketchpad for Professionals of the Built Environment
## 3 Evaluating City Ditty with a Usability Study
### Presence  
According to the presence model, immersion--as facilitated through realistic audio and visuals--must be present to elicit a plausible interpretation of the world, which in turn, facilitates a realistic response from the user. All participants indicated that visuals were _\"good enough\"_ but were quite impressed with the realism of the audio (including distance attenuation), which even compensated for the lower fidelity visuals. e.g., [P03]: _\"[The visuals] obviously weren't hyper realistic, but I like it. It did what it needed to do. Basically, I was never limited by how it looked... It still felt pretty realistic... The sounds were really good. That kind of made up for the fact that it wasn't like you're looking at like an actual tree.\"_ Participants further commented on the role of sounds in presence, creating the illusion of \"being there\". [P01]: _\"You could really feel most of the sounds you hear in the city.\"_ [P02]: _I think the construction noise was spot on. [Laughing] I was like, oh, [PERSON], there's construction. That's [my city]!\"_.  
The presence framework next suggests that if a suitable degree of immersion is provided within a plausible environment, people will respond similar to how they would in real life. Different aspects of this were identified when discussing the audio and visual aspects with participants. Participants were at times pleasantly surprised at the realism, noting how the environment responds to their actions in different ways. [P04]: _\"I moved the time of day [slider] before [the tasks] told me to and I was when I was like, 'oh, I wonder if this will change the traffic or different things like that', then sure, enough, yeah, that changes different things. Every kind of intuitive thought that I had was something that was covered later.\"_  
However, this high contextual realism also set high expectations that made anything that seemed 'off' extra noticeable and distracting to the user. [P05]: _\"I mean, people don't move, so it sometimes feels like it's not standard... the cars move so I kept asking myself why doesn't the person move? But you can hear them talk, so that's a good start.\"_  
To participants, the missing or slightly off aspects really stood out and were commented on with some disappointment but understanding that it was an early prototype. Beyond people and traffic, some participants pointed out that several pubs and cafes played music, but there were a lot of similar but silent businesses. Three participants listened for sounds from trees, with one even manipulating the wind intensity to see if there was a difference. Interestingly, P06 noted that although the instructions were in English, the people in the city centre spoke French, reminding them that they were in a virtual environment. These breaks in presence might distract the users from their tasks.  
Two participants also enquired about some issues relating to the ecological validity of the simulations. P01 pointed out from personal experience that the sounds of traffic should be much more intense at various times of the day than the software provided. As such, while City Ditty can currently help PBEs with _general_ sound awareness and general prototypes, it could later benefit from using real traffic and sound level data to facilitate fully fledged traffic studies and help facilitate more accurate design decisions.  
Participants were also asked if it sounded like anything was missing from the city that would help make it feel more realistic. All six participants specified that occasional car honks and a greater variety of vehicles would be more realistic, although the absence of these did not bother people as much as the breaks in presence. Other moving objects such as bicyclists, animated pedestrians, and small animals would also be beneficial.