## 4 Discussion
Studies have shown that sessions of art making can reduce experienced anxiety significantly [27; 28], although the amount of studies regarding the subject remains limited. The application used in this study is, however, a relatively passive experience for the user. The user does interact with the application with head movements, as most of the animations appear in the direction the head-mounted display is facing, but the user has no control over the contents or timing of the animations or soundscapes. Therefore, it should not be considered as a tool for making art. For art therapy purposes, more interaction and user control over the contents of the experience would plausibly increase the therapeutic quality of the product, especially regarding user groups that are in need of activating psychiatric treatment for anxiety. The sound design of Binaural Odyssey is simplistic, consisting only of the background sound ambiance which consisted of different binaural ambient sound loops played out in a seemingly random order. However, the participants were generally more pleased with the sounds than the visual side of the application, as sounds gathered several positive remarks from the participants and no negative notions. We estimate that the spatial nature of the soundscape is an important factor regarding the experience in this method, as it encourages the user to look around, and increases the feeling of being in a 3D abstract virtual space, due to providing a novel audio experience that reacts to the head movements similarly to real environments. The initial stress level of the participants seemed to correlate negatively to the grade given to the experience, but no correlation to measured effects of the intervention could be found. This indicates that the stress level of the participant has no significant effect to the therapeutic qualities of this method, although the evidence can be considered weak and more research with a larger study sample and with more variety in PSS-10 results would be required to confirm this finding. To gain further insight, we compared the effects of the method studied regarding HRV to similar studies that involved therapeutic relaxation applications. [PERSON] et al. [29] used a similar research setup to study physiological responses and user feedback on two breathing training smartphone applications by comparing the HRV data regarding baseline and intervention measurements. Unfortunately, no post-intervention data was collected in this study, but [PERSON] et al. found that measures of SDNN and RMSSD increased very significantly during the interventions. This is no surprise, as deep breathing is one of the main methods to reduce stress and increase relaxation. Similarly, [PERSON] and [PERSON] [30] concluded in their study that the use of Himalayan singing bowls significantly and relatively linearly increased RMSSD and decreased SI values during a 20 min relaxation session when compared to starting values, but their research as well did not include post-intervention measures. However, it is noteworthy that the method Binaural Odyssey uses seems to cause the opposite effect during the intervention, and the elevated SDNN and RMSSD values appear only after the intervention. Interestingly, [PERSON] et al. [31] stated in their study of virtual reality applications and stress recovery at the workplace that HRV parameters did not show a significant difference between pre-intervention, intervention, and post-intervention conditions, even though other post-intervention measures indicated increased relaxation. One reason for this might have been the variable chosen to analyze HRV, which was the LF/HF ratio.