# An Intelligent Condition Monitoring Approach for
## 4 Application and Results
### Experimental Rig Setup and Data Collection
#### 4.1.2 Noise Acquisition Method for Shearing Machines  
The shearing machine, a complex piece of mechanical equipment, possesses many sound sources. The noises of a shearing machine can be divided into working noises and unloaded noises. The working noises mainly include shearing noises and tool-retracting noises. The unloaded noises are generated by the shearing machines during unloaded operation, e.g., noises generated by the hydraulic and pneumatic system, noises generated during loading and transport of material, and noises caused by clearance of transmission components such as gears, push chains, bearings, and tool carriers. The composition of shearing-machine noises is shown in Figure 7.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Maximum** & **Maximum** & **Tool Feeding** & **Feeding Step** & **Section Size** \\
**Pressing Force** & **Shearing Force** & **Speed** & **Distance** & **Section Size** \\ \hline
165 kN & 785 kN & 0.03 m/s & 15 mm & 65 \(\times\) 65 mm \\ \hline \hline \end{tabular}
\end{table}
Table 1: The main parameter settings of the simulated shearing experiment.  
Figure 5: The simulated shearing machine.  
Figure 6: The simulated fuel assembly.  
The acquisition period equalled a complete working cycle of the shearing machine including feeding process, shearing process, and tool-retreating process. Figure 8 shows a diachronic sound pressure curve of the working cycle of a shearing machine. The curve clearly indicates the unloaded noise, shearing noises, and tool-retreating noises. It is obvious that the shearing noises are most intense.  
The moving-coil microphone has excellent anti-irradiation properties because it has no electronic components or integrated circuits inside. Furthermore, benefitting from the high peak voltage of its output signal, the ionizing noises caused by radiation have no significant effect on the signals. Experiments showed that the moving-coil microphone can work without significant distortion after receiving a total dose of 5.7 kGy [41]. In this study, the TS-5 moving-coil microphones (made by Guangdong Takstar Electronic Co., Ltd., Huizhou, Guangdong, China) were chosen as the components of the noise-acquisition unit, as shown in Figure 9.  
To reduce the influence of background noises and operation noises, the noise-acquisition unit was designed as a dual microphone. Microphone A was positioned near the shearing machine while microphone B was positioned far away, as shown in Figure 10. As the distributions of background noises are uniform, the difference of the background noises picked up by the two microphones is not significant, while the energy and pressure of the working noises produced by shearing machines decrease fast with the increasing distance from the sound sources. Therefore, the working noises picked up by microphone A are much stronger than that of microphone B. Thus, using the difference between the two sound channels, the signals are denoised.  
Figure 8: Diachronic sound pressure curve of a working cycle.  
Figure 7: Composition of shearing-machine noise.  
Figure 9: TS–5 type moving-coil microphone.  
After the denoising, the PCI-6280 data acquisition card (made by National Instruments Corporation, Austin, TX, USA) was used for digital sampling of the signals. The spectrum analysis of the noise signals showed that the energy is mainly within 7 kHz, and the maximum frequency does not lie above 20 kHz. According to the Nyquist theorem, the sampling rate is at least two times higher than the highest frequency of the analyzed signals. Hence, the sampling rate was set to 44.1 kHz. The sampled data are saved as \".wav\" audio files.