# A Biologically Inspired Sound Localisation System Using a Silicon Cochlea Pair
## 3 Experiment and Evaluation
### Results and Comparisons
For example, the 500 Hz to 8 kHz frequency range shows smaller standard deviation than the 40 Hz to 8 kHz frequency range at \(-90^{\circ}\) when the diagonal correlogram is used, which indicates our simplest hardware implementation is sufficient for this task. Table 4 shows comparisons of the proposed system with other biologically inspired sound localisation systems [26, 63, 64]. Human sound localisation performance reported in Reference [65] is also included in the table. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline  & & & \multicolumn{10}{c}{**Standard Deviation**} & \multicolumn{10}{c}{**Avg.**} \\  & & \(-90^{\circ}\) & \(-75^{\circ}\) & \(-60^{\circ}\) & \(-45^{\circ}\) & \(-30^{\circ}\) & \(-15^{\circ}\) & **0**\({}^{\circ}\) & \(15^{\circ}\) & \(30^{\circ}\) & \(45^{\circ}\) & \(60^{\circ}\) & \(75^{\circ}\) & \(90^{\circ}\) & **Enror (\({}^{\circ}\))** \\ \hline CAR-FAC & Linear & 33.65 & 29.16 & 18.12 & 18.30 & 18.88 & 17.67 & 15.66 & 19.57 & 19.42 & 21.28 & 22.86 & 27.04 & 24.50 & 19.05 \\ Non Quantised & ELM & 22.90 & 17.12 & 11.64 & 13.24 & 12.11 & 11.81 & 11.75 & 11.87 & 14.50 & 12.34 & 12.87 & 18.92 & 15.41 & 13.34 \\ Correlation & CNN & 6.03 & 5.35 & 4.82 & 4.04 & 3.19 & 1.92 & 0.50 & 1.26 & 1.00 & 0.60 & 0.45 & 3.03 & 4.32 & 2.87 \\ \hline CAR-FAC & Linear & 29.00 & 24.90 & 23.13 & 24.64 & 19.63 & 17.00 & 15.81 & 27.56 & 17.70 & 19.59 & 20.24 & 27.62 & 27.10 & 18.76 \\ Quantised & ELM & 17.58 & 15.67 & 10.87 & 10.21 & 11.07 & 10.99 & 8.05 & 10.52 & 10.68 & 11.88 & 14.51 & 16.40 & 13.30 & 13.06 \\ Correlation & CNN & 11.37 & 3.03 & 4.96 & 3.86 & 1.04 & 2.79 & 2.02 & 1.92 & 1.16 & 1.94 & 0.61 & 2.32 & 5.22 & 3.11 \\ \hline CAR Non & Linear & 16.98 & 16.70 & 19.18 & 18.44 & 19.39 & 19.61 & 13.66 & 17.83 & 27.81 & 20.99 & 17.83 & 26.00 & 28.10 & 16.84 \\ Quantised & ELM & 11.53 & 11.23 & 9.10 & 11.10 & 12.15 & 8.92 & 9.51 & 9.9 & 11.55 & 9.87 & 10.92 & 18.96 & 11.40 & 9.35 \\ Correlation & CNN & 2.76 & 0.99 & 4.21 & 4.80 & 0.84 & 2.66 & 0.38 & 0.58 & 0.39 & 0.16 & 0.31 & 1.91 & 0.33 & 1.25 \\ \hline CAR & Linear & 24.05 & 20.30 & 23.38 & 16.50 & 14.01 & 17.41 & 14.06 & 17.79 & 17.00 & 20.61 & 19.41 & 21.20 & 20.86 & 16.52 \\ Quantised & ELM & 12.45 & 10.36 & 9.92 & 8.69 & 8.21 & 7.53 & 5.46 & 7.84 & 7.04 & 11.28 & 8.81 & 11.80 & 10.32 & 8.34 \\ Correlation & CNN & 6.96 & 4.04 & 3.90 & 2.64 & 0.17 & 0.45 & 0.00 & 0.26 & 0.16 & 0.16 & 0.22 & 3.95 & 1.40 & 2.74 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Regression results. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Diagonal Correlogram**} & \multicolumn{2}{c}{**2\(\times\)2**} \\ \multicolumn{2}{c}{**Max-Pooling Correlogram**} \\ \cline{2-6}  & & **RMS Error (\({}^{\circ}\)) 0–45\({}^{\circ}\)/45–90\({}^{\circ}\)** & **RMS Error (\({}^{\circ}\)) 0–45\({}^{\circ}\)/45–90\({}^{\circ}\)** \\ \hline CAR-FAC & 45 Hz–8 kHz & 2.78/5.60 & 4.88/9.15 \\ Non-quantised Correlation & 500 Hz–8 kHz & 4.48/6.86 & 3.02/6.22 \\ \hline CAR-FAC & 45 Hz–8 kHz & 2.92/7.12 & 3.51/7.62 \\ Quantised Correlation & 500 Hz–8 kHz & 2.21/6.88 & 2.44/6.62 \\ \hline CAR & 45 Hz–8 kHz & 2.55/3.28 & 4.39/5.41 \\ Non-quantised Correlation & 500 Hz–8 kHz & 1.92/3.79 & 2.72/4.83 \\ \hline CAR & 45 Hz–8 kHz & 1.82/5.97 & 2.82/4.26 \\ Quantised Correlation & 500 Hz–8 kHz & 3.18/3.70 & 3.46/4.21 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Regression results. Figure 10: CNN results with different CAR configurations and different quantised correlogram inputs. \begin{table}