This thesis aimed to clarify the essential factors involved in externalising audio over headphones. Extensive research was conducted, examining binaural cues and the latest advancements in the field. A novel approach was proposed, which applied HRIRs and BRIRs on a Mid-Side decomposition. The objective was to enhance frontal externalization while increasing control over centre-panned and side-panned elements. The proposed method underwent rigorous testing in various setups, accompanied by objective and subjective evaluations. The objective measures were then correlated with the findings from the subjective evaluations. Interaural coherence analysis revealed that the BRIR exhibited lower overall coherence values than the HRIR. This was anticipated, considering BRIRs capture room acoustics that impact sound perception compared to anechoic conditions. Introducing simple room acoustics, such as early reflections and reverberation tails, significantly reduces the coherence in higher frequencies for HRIR. Connecting these findings to the conducted listening test, it is observed that lower IC generally corresponded to a wider audio configuration. However, assessing frontal externalization proved challenging. Among the tested configurations, the two BRIR models achieved the most width, with the unsmoothed version performing slightly better. This suggests a tradeoff between externalization and colouration, as the smoothed BRIR model excelled in spectral colouration and preference. For the HRIR, adding room acoustics slightly increased the width. It received lower ratings regarding spectral colouration and was not preferred over the HRIR model without room acoustics. This reinforces the significance of preserving the original spectral characteristics. / Denna avhandling hade som mål att klargöra de väsentliga faktorer som är involverade i att externalisera ljud över hörlurar. Omfattande forskning genomfördes, där binaurala ledtrådar och de senaste framstegen inom området undersöktes. Ett nytt tillvägagångssätt föreslogs, där HRIRs och BRIRs applicerades på en Mid-Sid-uppdelning. Målet var att förbättra frontal externalisering i kombination med mer kontroll över centrerade och sido-justerade element. Den föreslagna metoden genomgick rigorösa tester i olika inställningar, åtföljda av objektiva och subjektiva utvärderingar. Objektiva mätningar korrelerades sedan med resultaten från de subjektiva utvärderingarna. Analysen av interaural koherens visade att BRIR hade lägre övergripande koherensvärden än HRIR. Detta var väntat eftersom BRIR fångar upp rumslig akustik som påverkar ljuduppfattningen jämfört med anekoiska förhållanden. Att införa enkla rumsliga akustikegenskaper, såsom tidiga reflektioner och efterklangssvansar, minskar signifikant koherensen i högre frekvenser för HRIR. Genom att koppla samman dessa resultat med de genomförda lyssningstesterna kan man observera att lägre interaural koherens generellt korresponderade med en bredare ljudkonfiguration. Dock visade det sig vara utmanande att bedöma frontal externalisering. Bland de testade konfigurationerna uppnådde de två BRIR-modellerna störst bredd, där en icke spektrum-justerad version presterade något bättre. Detta tyder på en avvägning mellan externalisering och färgning, eftersom den slätade BRIR-modellen presterade bra i både färgning av ljud och preferens. För HRIR ökade bredden något genom att lägga till rumslig akustik. Den fick lägre betyg avseende spektralfärgning och föredrogs inte framför HRIR-modellen utan rumslig akustik. Detta understryker vikten av att bevara de ursprungliga spektrala egenskaperna.

Based on previous research on spatial attributes in foley and the concept that auditory immersion in first-person perspective computer games is enhanced by believable sound effects, this study explores if there is a connection between stereo foley and the believability of the first-person perspective, and regardless, if there is a preference to either mono or stereo foley. An interactive listening test was created in unreal engine 4, where 20 subjects, all considered gamers, played three levels that differed visually and in auditory content. In these levels, subjects auditioned two versions of avatar-related foley sounds. One version was mono, the other stereo. The test prompted the subjects to complete two tasks for each level, whereupon the foley version changed upon completion of the first task. The subjects then answered questions in between each level, regarding the foley version. They were asked to rate believability and choose a preference, as well as provide motivations for their choices. The quantitative data showed next no evidence that either mono or stereo was generally perceived as more believable or preferred. However, the qualitative data indicates that the majority of players tend to prefer and rate stereo foley as more believable in certain game environments. Furthermore, the data indicates that some subjects prefer a sensory replication of reality in foley. It is also shown that preference for stereo width vary between subjects and therefore argued that there cannot be a perfect standardized setting for stereo foley.