## 2 Application of Particle Dampers
Like [PERSON] et al. [19], they have also reported that the particle damper with a higher density is more effective for vibration attenuation. The application of particle dampers in the automotive industry can be seen in the work of [PERSON] et al. [25]. In their investigation, it has been shown that sand particles are effective for broadband vibration attenuation of an automotive engine oil pan. The authors have also shown that the particle damping mechanism and not the additional mass is the main reason for the oil pan vibration attenuation. Furthermore, it has been demonstrated that the position of the granular materials plays a major role in reducing the vibration amplitude. In their investigation, they have observed that the damping behavior of the structure can not be improved tremendously just by increasing the amount of sand in the cavity. The influence of granular material distribution for reducing the vibration amplitude of an oil pan has been experimentally investigated by [PERSON] et al. [17]. For this purpose, the authors have replaced the original bottom of the oil pan with a honeycomb bottom. The experimental observation shows that filling the granular materials at the position with the highest vibration amplitude is the best choice for vibration attenuation. Furthermore, the authors have studied the influence of sand with three different particle size distributions and observed that the larger grain size distribution is more efficient in reducing the vibration amplitude. They have concluded that the uniform distribution of the granular materials also shows remarkable results. This uniform distribution approach can be implemented if the vibration behavior of the primary structure is unknown, which is also a less mass-efficient solution. The study has also shown that the granular material distribution pattern obtained numerically is as powerful as the optimal distribution obtained experimentally. The authors have also demonstrated the efficiency of a partially filled honeycomb structure in reducing the vibration amplitude and sound emission of a running engine. In the proceeding investigations, the project team has studied the influence of different granular materials for reducing the vibration amplitude in general [26], as well as in the context of a wind turbine blade structure [18]. The experimental observation shows that rubber granulate is more effective for damping the wind turbine blade test specimen than stone powder and plastic balls. Furthermore, rubber granulate with four different grain sizes has been experimentally investigated to study the effect of the particle size on vibration attenuation. The experimental observation shows that rubber granulate with a larger particle size is more effective for vibration amplitude reduction in comparison to the rubber granulate with smaller particle size. In another study [26], it has been shown that particle dampers are more effective in reducing the vibration amplitude of the primary structure of an electric engine in comparison to several acoustic damping foam materials. Another automotive application of particle damping to reduce the noise and vibration of electric motors was developed by [PERSON] [20]. The author has specifically designed a particle damper to suppress the high-frequency torsional vibration mode of a motor. His investigation shows that the currently used expensive elastomeric tuned mass damper can be replaced with a cost-effective particle damper. Implementation of particle dampers in a mining truck can be seen in the work of [PERSON] et al. [27]. In their study, it has been observed that particle dampers can reduce the vibration amplitude of the structure more effectively for a higher engine speed. [PERSON] et al. [28] have successfully used tungsten particles of diameter 0.5 mm on a commercial banknote processing machine. Their experimental observation shows that the tungsten particles are effective for the frequency range between 2 kHz to 12 kHz. [PERSON] et al.