# Head-Related Transfer Functions for Dynamic Listeners in Virtual Reality
## 6 Discussion
### Static Localization  
In Experiment I, no clear improvement was found in static localization accuracy when using individual HRTFs. Our third hypothesis receives partial support from the non-significant (\(p=0.083\)), but moderate effect size, of reduced quadrant errors percentage  
Figure 5: Subjective scores from the 6-DoF VR experiment. Panels (**a**–**d**) display results from the localization scenes, panels (**e**,**f**) timbre scenes, and panels (**g**,**h**) overall quality scenes. The error bars denote the bootstrapped 95% confidence intervals of the mean and the letters denote the significant differences (\(p\leq 0.05\)) between conditions calculated by pairwise permutation tests. Conditions with the same letter are not significantly different from each other. with individual HRTFs (measured 19%, modeled 18%) compared to the generic HRTFs (22%). In previous literature, using static localization tasks, [PERSON] [4] showed a reduction in quadrant errors from 21% to 8% when switching from generic to individual HRTFs, [PERSON] and [PERSON] [40] a reduction from 11% to 6% when switching from individual HRTFs to free field, and finally [PERSON] et al. [2], moving from generic HRTFs to free field conditions, a change from 31% to 19% of front-back confusion percentage. However, some studies show no effect in quadrant errors rate between individual and generic HRTFs, for example, [PERSON] et al. [8] 59% and [PERSON] [3] 28% for both HRTF types. There, especially the level of participant training in localization tasks has been suspected to mask the differences in HRTF cues. Considering a commercial scenario, most users are likely to be untrained, non-expert listeners, which might further minimize the localization benefits of individual HRTFs. Although not showing a significant reduction in quadrant errors percentage, our results appear to be in line with what may be expected to be the range of quadrant errors in static localization tasks using individual or generic HRTFs. After cleaning the data from quadrant errors, the azimuth error angles should be approximately the same between HRTFs and free-field listening based on previous research [2, 3, 40]. For headphone localization tasks using either generic or individual HRTFs, the values found in previous research range from 15\({}^{\circ}\) to 22\({}^{\circ}\)[4, 8]. These values may be contrasted with free field localization results, which yielded azimuth errors of 11\({}^{\circ}\) on average in [4]. The results for average local azimuth errors in our static localization experiment varied between 17\({}^{\circ}\) and 21\({}^{\circ}\) depending on the HRTF set, which is in line with previous results. Similar to previous work, we found no statistically significant difference between the HRTF sets in the average azimuth error. However, previous studies on static localization comparing individual and generic HRTFs have found significant differences in elevation localization accuracy in favor of the individual HRTFs [3, 4], but also a lack of an effect is reported [8], where an average elevation error value of 18\({}^{\circ}\) was found for both individual and generic HRTFs. In our static localization experiment, no significant reduction in unsigned elevation errors was observed when switching from generic HRTFs to either of the individual sets, which is in contrast with the majority of previous results. The values we found for average unsigned elevation errors ranged from 21\({}^{\circ}\) to 26\({}^{\circ}\) for the different HRTF sets. Some exemplary elevation error values found in the literature for static localization are 10\({}^{\circ}\) or 21\({}^{\circ}\) in the free field [4, 9], 11\({}^{\circ}\), 29\({}^{\circ}\), or 37\({}^{\circ}\) using individual HRTFs [4, 9, 41], and 42\({}^{\circ}\) using generic HRTFs [4]. Comparing absolute localization accuracy results between studies is challenging due to different stimulus signals, target locations, pointing methods, visual settings, and participant training.