# Preprocessing Acoustic Emission Signal of Broken Wires in Bridge Cables
## 3 Results
### Comprehensive Noise Analysis  
#### 3.3.1 Time Domain Analysis  
The following analysis of the noise signal was carried out in the time domain:  
1. Impact-amplitude correlation analysis;  
Unlike the ringing count of a signal, when an AE signal waveform reaches its maximum value, an impact is formed at that value. Through the impact-amplitude correlation analysis, the distribution interval of the collected noise amplitude can be derived. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Serial** & **Rise Time** & **Duration** & **Ringing** & **Amplitude** & **Energy** & **AF** & **ASL** \\
**Number** & **(\(\mu\)s)** & **(\(\mu\)s)** & **Count** & **(dB)** & **(ms*mV)** & **(kHz)** & **dB** \\ \hline
1 & 11,949 & 12,396 & 13 & 53 & 2.86 & 1.05 & 28 \\  
The impact-amplitude correlation plots of the noise signals of the three bridges are shown in Figures 8-10. Figure 8: Impact-amplitude correlation diagram of cable noise signal of Yangma Island Bridge. Figure 9: Impact-amplitude correlation diagram of cable noise signal of Yellow River Bridge. The impact count amplitude of the noise signal collected from each bridge is normally correlated, with few high and low amplitude signals. The amplitudes of noise at each bridge mainly concentrate between 50 dB and 70 dB. We notice that the noise signal at 80 dB of Yangma Island Bridge did not cause impact and few impacts occurred with the noise between 80 dB and 90 dB at the other two bridges. Therefore, according to the distribution of the impact-amplitude correlation diagrams of the three bridges, the threshold for filtering noise can be set at 80 dB. Then, most of the noise can be filtered out by segmentation analysis after 80 dB. 2. Ringing count-duration correlation analysis;  
Although the amplitude is the main reference parameter for signal filtering, there may still exist cases where the signal amplitude is high but the ringing count or duration is short. Thus, other characteristic parameters are needed as the basis for filtering the noise signal. The ringing count reflects the number of pulses above the analysis threshold (45 dB) of a noise signal, representing the intensity and frequency of the noise signal. A high ringing count within a short duration indicates that the signal energy release is concentrated. The correlation analysis of the two characteristic parameters can provide a reference to the noise filtering in the time domain, and the noise signal with high energy in a short time can be filtered out by setting the appropriate time parameters. Figures 11-13 depict the noise signal duration and ringing count correlation analysis for the three bridges. From the ring count-duration correlation diagram of the noise signals of the three bridges, it can be observed that there is an obvious positive correlation between the magnitude of the ringing count and the duration, except for the fact that the noise signal is the least obvious at Yellow River Bridge. The duration and ringing counts of the noise signals collected at the three bridges are relatively small, and the noise signals generally complete the ringing counts within 0.15 s, i.e., the main energy of the signal can be released within that time. Therefore, the duration of 0.15 s and the 1000 ringing counts can be used as the threshold indicators for filtering noise signals. Signals smaller than this duration and ringing counts can be identified as noise. Figure 10: Impact-amplitude correlation diagram of cable noise signal of Caihong Bridge. Figure 11: Ring count-duration correlation diagram of cable noise signal of Yangma Island Bridge. Figure 12: Ring count-duration correlation diagram of cable noise signal of Yellow River Bridge. Figure 13: Ring count-duration correlation diagram of cable noise signal of Caihong Bridge. Amplitude-energy correlation analysis;  
Figures 14-16 depict the amplitude-energy correlation analysis of the noise signals of the three bridges. The intensity of the AE source is directly related to the magnitude of the AE signal.