A method for studying the effect of diegetic vs. non-diegetic rating interfaces on the assessment of virtual acoustic environments

Auditory perception experiments conducted in VR come along with a high degree of ecological validity while maintaining a controlled laboratory setting. However, since the participant's vision is occupied during simulation, conventional evaluation instruments like rating scales need to be relocated to the virtual environment to allow for immediate stimulus rating. This can be achieved either by the use of diegetic interfaces, which are implied to be a part of the simulation (e.g., a screen held by the participant's avatar) or non-diegetic interfaces, which do not claim to originate from the simulated reality (e.g., sliders and text elements laid on top of the participant's view). It is unknown whether the choice of interface does affect the participant's perception of the virtual environment - including its acoustic components. To address this shortcoming, a methodological study is presented. Participants are exposed to a virtual scenario simulating an urban green area with nearby ambience sound sources. In this setting, they are provided with diegetic and non-diegetic rating interfaces to assess the acoustic environment. Subsequently, perceived presence and involvement in the virtual environment are surveyed as well. This way, the study provides useful guidelines for future VR experiments assessing soundscape-related aspects of perception.