## 3 Experiment Setup
### Experiment Process  
#### 3.2.1 Flight Plan  
The experimental environment and flight conditions of this study were formulated so that each damage flight test dataset was completed under the same environment and restrictions, thereby ensuring the consistency of the environment for capturing flight data from the quadcopter.  
First, the flight tests were carried out in an open outdoor area with wind speed below 2 m/s and a flight time of 10-11 minutes. Second, to ensure that the flight test was not affected by insufficient power, the voltage of each battery in each flight test was not less than 3.7 volts. Third, the flight experiment used in this study was set at \"Loiter Mode\" to maintain the current position, heading, and altitude of the experimental drone. This  
\begin{table}
\begin{tabular}{c c} \hline \hline Motor & \
\begin{tabular}{c} The audio recording sensor is shown in Figure 3. The recording format was \\ LPCM 44.1 kHz, 16 bit/MP3 128 KBPS, and the frequency response was \\ 40–16 kHz with the sampling frequency of 44.1 kHz. The output power of \\ the audio sensor is 200 mW, the playback format is MP3, \\ and its weight is about 82 g. \\ \end{tabular} \\ \hline Computer &
\begin{tabular}{c} Windows 10 was the operating software using a system processor of \\ Intel(R)Core(TM)i7-7700 CPU, memory (RAM) of 16 GB, 64 bit operating \\ system, and x64 type processor. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 2: The introduction of the audio sensor and the computer used.  
Figure 3: Signal acquisition by audio sensor.  
\begin{table}
\begin{tabular}{c c} \hline \hline \multirow{2}{*}{Motor} & \begin{tabular}{c} Commercially available T-motor Air Gear 450 multi-rotor power set, which contains DC \\ motor and propeller. The brushless DC motors are AIR2216 with a KV value of 880. \\ \end{tabular} \\ \hline Propeller & \begin{tabular}{c} A self-tightening propeller of the T1045 model was selected with the specification of a \\ 10-inch blade and pitch of 4.5\({}^{\circ}\); constructed from nylon and glass fiber. \\ \end{tabular} \\ \hline Electrical speed controller & \begin{tabular}{c} The electronic transmission was a T-motor AIR 20A with a continuous current of 20 A. \\ \end{tabular} \\ \hline Flight controller & \
\begin{tabular}{c} The flight control module mounted on the drone was a Pixhawk 2 produced by HEX, which \\ was equipped with Ardupilot V3.6.7 [13] open-source firmware, as shown in Figure 2b. \\ The processor used a 32-bit ARM Cortex M4 core, and memory (RAM) and flash memory \\ were 256 KB and 2 MB, respectively. Pixhawk 2 includes 3 inertial measurement units \\ (IMUs), an accelerometer, and a magnetometer, barometer, and gyroscope. The Mission \\ Planner is used as ground station [14]. \\ \end{tabular} \\ \hline GPS &
\begin{tabular}{c} A GPS receiver was chosen from the GPS positioning and navigation module produced by \\ HEX, as shown in Figure 2c. This uses a Ublox NEO-M8P chip module, which can receive \\ satellite systems such as GPS and GLONASS. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 1: The introduction of the components of the drones.  
mode must have a GPS with a 3D-position fix and Horizontal Dilution of Precision (HDOP) below 2.0. Fourth, an additional audio sensor was installed on the quadcopter, and the microphone was positioned at the proximity of motor.  
The flight path of the quadcopter was planned using Mission Planner software and by loading path files. Seven commands for path planning were used in this study. Four waypoint positions were designed and each waypoint had a radius of two meters with height of five meters.