## 4 Discussion  
This pilot study evaluated the potential of a novel virtual reality based serious game as an intervention tool for auditory hypersensitivity in individuals with autism spectrum disorder. SoundFields is the first application of this type to combine VR and game mechanics to deliver an exposure therapy framework for this issue. Another novel aspect is the use of head tracked binaural based spatial audio as a rendering technique to present feared auditory stimuli to the user. Similar to the use of realistic visual three-dimensional stimuli rendered in VR for desensitisation to specific phobias and environments that may provoke anxiety in individuals with autism [66; 67; 68], SoundFields produces realistic three-dimensional auditory stimuli that can simulate the movement and acoustic environments of feared sounds. For any form of VRET to be considered successful, the virtual environment must be capable of eliciting emotions such as anxiety in order for new positive associations \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Participant** & **Stimulus** & **Session 1** & **Session 2** & **Session 3** & **Session 4** \\ \hline A & Group Singing & 71.45 & 44.39 & 68.13 & 100.98 \\  & Baby Crying & 43.00 & 57.74 & 89.45 & 81.57 \\ B & Group Singing & 92.00 & 75.03 & 60.03 & 84.26 \\  & Children Streaming / Shouting & 71.45 & 44.39 & 68.13 & 100.98 \\ C & Children Screaming / Shouting & 65.84 & 61.31 & 23.06 & 71.82 \\ D & Sirens & 70.32 & 41.91 & 93.87 & 100.53 \\  & Children Screaming / Shouting & 89.02 & 63.55 & 84.20 & 100.87 \\ E & Children Screaming / Shouting & 38.46 & 45.04 & 53.19 & 51.93 \\ F & Children Screaming / Shouting & 100.07 & 73.03 & 99.30 & 99.15 \\  & Baby Crying & 82.21 & 78.41 & 99.95 & 92.55 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Participant tracked interaction time for each target stimuli across all four experimental sessions, represented in seconds. Figure 8: Box plot displaying the tracked interaction time with target stimuli for all participants across each session. with the stimuli to be formed through controlled and graduated exposure [69]. The current study found that all of the target stimuli activated a level of anxiety in participants during baseline measurements which resulted in the lower scores reported in the \"Smiley-Face\" assessment scale. These results are consistent with similar research conducted with neurologically healthy participants, reporting that the use of spatialised sound can activate the anxiety provoking structure [46; 47]. Furthermore, with the addition of the positive emotional response to non-target stimuli during measurements (see Figure 7), these results support the use of spatial audio in VR based therapy for auditory hypersensitivity. The presented intervention was successful in reducing the participants' perceived anxiety towards target auditory stimuli over four weekly playing sessions. This was evident from the significant decrease in the self-reported levels of anxiety scores in the pre- and post-study measurement sessions, which was the main outcome measure highlighted in Table 3 and Figure 7. This falls in line with similar research that reveals a reduction in stress associated with presented audio stimuli within a computer game environment [32]. Additionally, the increase in time participants voluntarily interacted with target stimuli can also be interpreted as an increase in tolerance. Results show a significant increase in tracked interaction time between sessions one and four. This is further supported by the implemented exposure hierarchy which moves the virtual sound stimuli closer to the participant. However, interestingly there is a drop in the amount of tracked interaction during session two (see Figure 8). This could be explained by the reduction in virtual distance between the participant and the target stimuli from 25 to 15 m, which would result in a perceptible rise in loudness after the first session.