## 3 Results
### Cluster Analysis
#### 3.2.2 Lab Experiment Result: Raw Data Clustering  
Figure 12 presents the elicited constructs along with their individual ratings for each position. Dendrograms resulted from cluster analysis are presented for both constructs and positions, showing the general interaction between different elicited terms.  
Seven clusters were found at an inter-cluster distance of 40, and 12 clusters at a distance of 20. It can be seen that the elicited attributes generally fall into a number of recurring categories, presented in Table 3. An initial observation showed an increased number of constructs describing timphal differences in the virtual test than in the in-situ test. It is believed that the ability to instantly switch between the stimuli facilitated the perception of such timphal characteristics, which describe either the source, the perceived reverberation or the room itself. Similar attributes as in the in-situ test could be extracted; For instance, in cluster 2 (Figure 12) elements describing the direction of the reverb and echoes are tightly clustered. Likewise, similar attributes can be observed in other clusters as well (No. 12, 73, 74, 80, 86). Among some of the clusters it can be noticed again that different verbalisations might refer to the same perceptual effect. In cluster 3.1, elements describing the direct sound can be recognised (No. 20, 23, 24, 25, 26, 27). Whether they refer to the perceived loudness of the source, intelligibility or spread, this seems to suggest that there might be a cause-effect relationship between the loudness of the source and its intelligibility or spread. A similar effect is seen in cluster 4.1, where the interaction between the source sharpness  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Cluster** & **Attribute** \\ \hline
1.1 & Source width/spread \\
1.2 & Reverb/Echo direction (Front/Side) \\
2 & Echo perception and direction/Source width/Envelopment \\
3.1 & Envelopment \\
3.2 & Environment size/Source distance/Reverb level \\
3.3 & Reverb spread/Envelopment/Reverb level \\
4.1 & Source/reverb focus/diffuseness/clarity \\
4.2 & Source Level \\
4.3 & Reverb Spread/Source clarity/Environment depth \\
5 & Envelopment/Reverb spread/Reverb direction \\ \hline \hline \end{tabular}
\end{table}
Table 2: In-Situ main construct categories based on clustering.  
(No. 34), intelligibility (No. 35, 36) and the perceived distance to source (No. 38, 39) is apparent within a cluster focused tightly around the direct sound. Interestingly, cluster 4.2 is also well focused around the reverberation. The elements describing the perception of the overall reverb loudness (No. 41, 42, 43, 44, 45) interact with the perceived reverb spread (No. 47), but also with the source width (No. 46). It is therefore apparent that there is a broad separation in the perception of source-related or room- related attributes, which is also in-line with [PERSON]'s \"Scene-Based Paradigm\" [10]. This might also be related to the ideas of source vs. room presence [41] and foreground vs. background stream [42], where early and late parts of a sound event produce different types of spatial attributes.  
Position clustering was carried out for the lab experiment results as well. As seen in Figure 15, four clusters could be observed bringing similarly rated positions together. In cluster 1 it can be seen that P1_0\({}^{\circ}\), P1_90\({}^{\circ}\) and P_180\({}^{\circ}\) are similarly rated by participants. Cluster 2.1 brings together P2_0\({}^{\circ}\) and P2_180\({}^{\circ}\), whilst in Cluster 2.2, positions P2_90\({}^{\circ}\), P3_90\({}^{\circ}\) and P4_90\({}^{\circ}\) are grouped together. Finally, P3_0\({}^{\circ}\) and P4_0\({}^{\circ}\) are included in cluster 2.3. These results are in complete agreement with the ones from the in-situ test, which seems to support the ecological validity of the laboratory experiment.