## 5 Experiment and Results  
### Experimental Setup  
The purpose of the experiment is to locate the sound source on the experimental platform. The experiment was carried out in a hemi-anechoic room. The experimental bench \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Calculation Type**} & **Single Reconstruction Point** & \multirow{2}{*}{**Increase Computations**} \\  & **Computations** & \\ \hline Index & M & 0 \\ multiplication or division & M (4 + 14 L) & 62 R \\ Square root & M & R \\ Trig (sin/cos) & 0 & 6 \\ Trig (tangent) & 0 & 2 \\ Index & M & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Computational complexity of single reconstruction point and the increase of combining stereo vision. contains a slowly rotating swing arm driven by a motor and a sound source. The rotation speed of the swingarm under the combined action of the motor and gravity gradually changes from the slow speed of climbing to the fast speed of descending. A Bluetooth speaker with a diameter of 10 cm is installed at the end of the swing arm as the sound source to be located on the experimental bench. The speaker plays a single-frequency sound with a frequency steadily. The depth images are obtained by Intel(r) RealSense(tm) D415 depth camera (Manufactured by Inter Corporation, Santa Clara, CA, USA). As shown in this section and the next, the camera can output a normal image obtained by a red, green and blue (RGB) sensor and a depth image obtained by stereo vision technology at the same time. The key specifications of the depth camera are presented in Table 2.  
The resolution used by the camera in this experiment is \(1280\times 720\) (\(r_{X}=1280,\theta_{HFOV}=69.4^{\circ}\)) and \(640\times 480\) (\(r_{X}=640\), \(\theta_{HFOV}=65^{\circ}\)), and the shooting frame rate is set to 10 _fps_. The depth accuracy of the reconstructed point required for beamforming depends on the camera accuracy, and the absolute error \(e\) of the measured value depth and the linear relationship of the distance [23]. \[e_{max}=\frac{2p_{s}\tan\left(\frac{\theta_{HFOV}}{2}\right)}{r_{X}l_{b}}\times z ^{2}=2.895774\times 10^{-6}\times z^{2} \tag{11}\]  
A spiral array composed of 24 microphones was used in the experiment and the diameter of the array was 0.8 m. The layout of the microphone array is shown in Figure 4. The microphones were MPA16. The sound signal was collected through the data acquisition instrument SCM05 of the LMS company with a sampling rate of 51.2 kHz. The rising edge of an external direct current (DC) signal was used as a trigger so that the image and sound signals were collected at the same time. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Depth Stream Output Resolution & Up to 1280 \(\times\) 720 \\ Depth Stream Output Frame Rate (Max) & 30 fps \\ Depth Field of View (FOV) & 69.4 \(\times\) 42.5\({}^{\circ}\) \\ Operating Range (Min-Max) & 0.16–10 m \\ Distortion & \(\leq\)1.5\% \\ Baseline (\(l_{b}\)) & 55 mm \\ Subpixel (\(p_{s}\)) & 0.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The key specifications of Intel RealSense D415. Figure 4: The 24 channel microphone array. The experiment used two layouts to test the effectiveness of the combined method. In layout 1, the plane of the microphone array was parallel to the plane of the test bench and the distance between them was 1.63 m. The camera and microphone array were placed on the lower right of the test bench. The resolution of the camera was 1280 \(\times\) 720, and the speaker played a single frequency sound of 1 kHz. In layout 2, the center of the microphone array was 1.99 m away from the center of the test bench. The angle between the plane of the moving sound source in the operating mechanism and the array plane was 30\({}^{\circ}\) to ensure that the sound source changed in the \(XYZ\) direction. The resolution of the camera was 640 \(\times\) 480, and the speaker played a single frequency sound of 3 kHz.