## 3 Results  
Levene and Shapiro-Wilk tests were first conducted, using the SPSS software, in order to determine the suitability of the collected data for parametric statistical analysis. The Shapiro-Wilk test showed that not all scores in each condition featured normal distribution, although the results of the Levene test showed homogeneity of variance for all sound sources. For these reasons, non-parametric tests were chosen for the statistical analysis. Wilcoxon signed-rank tests were used to examine the significance of difference between each presentation method for each source and for each ICTD since the experimental design was of a within-subject repeated measure (i.e., all subjects tested all conditions in a randomised order). Boferroni correction was applied to the \(p\) values that were obtained from the Wilcoxon tests to reduce a potential Type-I error in multiple comparison.  
Figure 3 shows the median perceived elevation of each of the test stimuli, plotted with notch edges (i.e., non-parametric 95% confidence intervals). With respect to the VLTs, it can be observed that each of the proposed band reduction methods, as well as the blanket threshold method, resulted in the perceived location of each stimulus being similar to that for the main layer only condition, suggesting that the proposed methods tend to fulfil their aim. This was the case for all sources, with the median difference in perceived elevation between the main layer only and the VLT conditions ranging between \(2.4^{\circ}\) and \(-4.0^{\circ}\) for the 0 ms ICTD and between \(3.9^{\circ}\) and \(-3.2^{\circ}\) for the 1 ms ICTD. Alongside this, the notch edges of the main layer only and VLT conditions all overlap, which suggests no significant differences among the conditions [30].  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Method** & **LAeq (dB)** \\ \hline FB & 70.0 \\
1 + B & 71.2 \\
4B & 72.2 \\
8B & 72.4 \\ Blanket & 70.4 \\
0 dB ICLD & 73.1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: A-weighted average sound pressure level (LAeq) for stimuli presented while using each localisation threshold method.  
The Bonferroni-corrected Wilcoxon tests indicated that, for all sources and ICTDs, none of the VLT methods had a significant difference to the main layer only condition. In addition, the effect size \(r\) did not indicate a large effect in any case (\(<\)0.5 for all). From this, it can be suggested that all of the proposed VLT methods successfully prevented vertical interchannel crosstalk from affecting the perceived location of the main channel signal.  
The medians for the 0 dB ICLD condition were generally higher than those for the main layer only condition (\(p<0.05\)), which was expected. However, it is interesting to note that the oboe did not follow this trend; there was no significant difference among all of the conditions (\(p>0.05\)). This result might suggest that the application of VLTs would not always be necessary and would have somewhat of a source dependency.  
A further result of note can be seen with respect to the main and height layer only conditions. Firstly, for the latter condition, it would appear that perceived elevation judgments were generally accurate for all sources, excluding the oboe, with respect to the physical position of the height layer. Conversely, the judgments were less accurate for the main layer only condition, with perceived source elevation being in the range of 5.8\({}^{\circ}\)-13.0\({}^{\circ}\) with respect to the main layer's physical position. This elevation of the sound source with respect to the main layer was also maintained for the conditions, whereby a VLT was applied to the height layer. The results of a [PERSON] signed rank test, which compared the results for the main layer only condition to the physical position of the main layer (0\({}^{\circ}\)), showed that each source was perceived to be significantly higher than the physical height from which the source was presented (\(p=0.000\) for all sources).