## 4 Discussion
### Lab Experiment Validity  
As discussed above, both the in-situ and lab experiment generated the same clusters in terms of listening positions and orientations. This is important in confirming the validity of the lab elicitation, meaning that in future research a virtual test can be used alone, with a higher efficiency and in a more controlled environment.  
The lab experiment was considered to overcome the shortcomings of an in-situ test where the switching of the stimuli cannot be done instantaneously. An initial observation of the elicited constructs showed an increased number of constructs describing timbral differences of different listening positions. It is considered that the ability to quickly switch between stimuli facilitated the perception of timbral differences, which might have been more subtle than spatial ones and therefore more difficult in the in-situ experiment. Fur  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Attribute** &
\begin{tabular}{c} **No. of** \\ **Occurrences** \\ \end{tabular} & \% & **Audibility Means** & \% & **Audibility Index** \\ \hline Quiet/Loud—Direct Sound & 6 & 75.00 & 78.75 & 78.75 & 76.88 \\ More/Less—Listener & 7 & 87.50 & 63.43 & 63.43 & 75.46 \\ Envelopment & & & & & \\ Wide/Narrow—Apparent Source & 6 & 75.00 & 66.00 & 66.00 & 70.50 \\ Width & 6 & 75.00 & 47.00 & 47.00 & 61.00 \\ Narrow/Wide—Reverb Spread & 6 & 75.00 & 47.00 & 47.00 & 61.00 \\ Close/Far—Source Distance & 2 & 25.00 & 85.50 & 85.50 & 55.25 \\ Quiet/Loud—Reverb & 5 & 62.50 & 46.05 & 46.05 & 54.28 \\ Central/Lateral—Echoes & 3 & 37.50 & 71.00 & 71.00 & 54.25 \\ Central/Lateral—Reverb & 3 & 37.50 & 63.50 & 63.50 & 50.50 \\ Bright/Dull—Reverb & 1 & 12.50 & 88.00 & 88.00 & 50.25 \\ Bright/Dull—Echoes & 1 & 12.50 & 88.00 & 88.00 & 50.25 \\ \hline Long/Short—Pre-Delay & 2 & 25.00 & 68.00 & 68.00 & 46.50 \\ Audible/Inaudible—Echoes & 3 & 37.50 & 55.33 & 55.33 & 46.42 \\ Boomy/Less-boomy—Reverb & 2 & 25.00 & 63.00 & 63.00 & 44.00 \\ Pleasant/Unpleasant—Listener & 1 & 12.50 & 75.00 & 75.00 & 43.75 \\ Encyclopedia & 3 & 37.50 & 49.83 & 49.83 & 43.67 \\ High/Low—D/R Ratio & 2 & 25.00 & 60.00 & 60.00 & 42.50 \\ Bright/Dull—Source & 1 & 12.50 & 67.00 & 67.00 & 39.75 \\ Front/Back—Reverb & 2 & 25.00 & 52.00 & 52.00 & 38.50 \\ Narrow/Wide—Environmental & 1 & 12.50 & 62.00 & 62.00 & 37.25 \\ Width & & & & & \\ Shallow/Deep—Environmental & 2 & 25.00 & 49.50 & 49.50 & 37.25 \\ Depth & 1 & 12.50 & 62.00 & 62.00 & 37.25 \\ Large/Small—Space & 1 & 12.50 & 62.00 & 62.00 & 37.25 \\ Clear/Muddy—Source & 2 & 25.00 & 48.00 & 48.00 & 36.50 \\ Long/Short—Reverb Time & 2 & 25.00 & 43.50 & 43.50 & 34.25 \\ Sharp/Diffused—Direct Sound & 1 & 12.50 & 55.00 & 55.00 & 33.75 \\ Narrow/Wide—Vertical Source & 1 & 12.50 & 55.00 & 55.00 & 33.75 \\ Wide & & & & & \\ More/Less—Vertical Reverb & 1 & 12.50 & 55.00 & 55.00 & 33.75 \\ Spread & 1 & 12.50 & 55.00 & 55.00 & 33.75 \\ High/Low—Source Elevation & 1 & 12.50 & 54.00 & 54.00 & 33.25 \\ More/Less—Top Reflections & 1 & 12.50 & 37.00 & 37.00 & 24.75 \\ Cold/Warm—Reverb & 1 & 12.50 & 35.00 & 35.00 & 23.75 \\ More/Less—Hollow & 1 & 12.50 & 29.00 & 29.00 & 20.75 \\ Front/Back—Echoes & 1 & 12.50 & 25.00 & 25.00 & 18.75 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Most salient attributes based on audibility index.  
thermore, the audibility-based filtering performed on the lab experiment results extracted a more focused set of perceived attributes. Recognising the benefit of audibility testing in an elicitation scenario, it is to be noted that it can only be performed in a lab-based framework where back-to-back assessment of stimuli is facilitated. Based on the aforementioned aspects, it can be affirmed that the use of a lab elicitation offers certain advantages in terms of robustness, scalability and efficiency while still maintaining the ecological validity of an in-situ test.