# Auditory Localization in Low-Bitrate Compressed Ambisonic Scenes
## 4 Results  
The collected directional data represents auditory localization of the virtual acoustic pointer adjusted to match the perceived direction of the virtual target sound sources. The responses were gathered during 104 listening tests consisting of 60 individual tasks each. Table 3 shows the number of participants who completed the tests, separated into subgroups by the reproduction method and audio content type used. The median time of completing each individual task by the participants was about 26 s. All the investigated low-bitrate compression conditions were compared within each of the six subgroups. Figure 4: 50-channel spherical loudspeaker array at the AudioLab, University of York. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Reproduction Method** & \multicolumn{2}{c}{**Loudspeakers**} & \multicolumn{2}{c}{**Binaural (Individual HRTFs)**} & \multicolumn{2}{c}{**Binaural (Generic HRTFs)**} \\ \hline Content Type & Simple & Complex & Simple & Complex & Simple & Complex \\ Number of Participants & 21 & 16 & 15 & 14 & 19 & 19 \\ \hline \end{tabular}
\end{table} 
Table 3: Number of participants who completed the tests grouped by the rendering method and audio content type used. Figure 5 shows the distribution of the acoustic pointer directions on the sphere set by participants. Each sphere represents data gathered for different directions of the target sound source presented using all three reproduction methods at different Ambisonic orders and compression bitrates. Figure 6 shows the same data plotted using equirectangular projection. Figure 5: Distribution of the acoustic pointer direction recorded during the listening test corresponding to each target source direction. The red dots symbolize directions of the target sound sources. The dashed magenta circles represent the respective cones of confusion on the sphere. The axes denote directions relative to the listener: red—front, green—left, blue—top. Figure 6: Distribution of the acoustic pointer directions recorded during the listening test corresponding to each target source direction. The red dots symbolize directions of the target sound sources. The dashed magenta lines represent the respective cones of confusion. The unfilled circles represent mean direction of the pointer directions. The initial pointer direction for each task was set straight in front of the listener. Since participants operated the azimuth and elevation controls (see Figure 3) independently, it can be seen that the distributions of recorded pointer directions are slightly skewed towards the horizontal and median planes. This suggests that responses may have been affected by the collection method. Directions one and two of the target virtual sound source correspond to the median plane directions of incidence. The respective recorded acoustic pointer indications are distributed close to the intersection of the median plane with the unity sphere. Perceived elevation of these sources and acoustic pointer can be matched by the listener using spectral and dynamic localization cues exclusively. Directions four and five correspond to slightly elevated and laterally shifted directions. Collected acoustic pointer indications are distributed along the intersection of respective cones of confusion with the unity sphere. Directions three and six correspond to slightly elevated and strongly laterally shifted directions, close to the interaural axis. Based on the visual observation, the distributions of pointer indications are rather concentrated around the target sound source directions with a slight skew towards the respective cones of confusion. Further analysis was conducted using great-circle distance, which can be calculated as the shortest angular distance between each pointer and corresponding target directions on the unity sphere. The analysis of horizontal and vertical localization error components was performed; however, the exhibited differences between codec conditions were less significant than when using the combined error metric.