## 5 Discussion of the Noise Control Strategies  
Derived from the clustering analysis of noise in the driver's cabin of Line 1 of the Lanzhou Urban Rail Transit, the noise patterns can be categorized into four distinct types based on intensity and frequency, as illustrated in Figure 8. This section delineates targeted and practicable noise control strategies for each specific category to effectively address the noise issues in the driver's cabin. Low-frequency, high-intensity noise (Cluster 1 and Cluster 3) primarily originates from mechanical structure and wheel-rail contact, particularly during the train's acceleration and deceleration phases. The friction between mechanical systems and the track generates high-intensity, low-frequency noise. To effectively address this issue, it is essential to apply advanced vibration dampers and elastic fasteners to diminish mechanical vibrations and friction noise, employ high-efficiency lubricants and technologies to minimize friction between mechanical components, and consistently maintain traction motors and braking systems to ensure their smooth operation. Specifically, the introduction of rail dampers and elastic fasteners across the track network can significantly reduce vibrations and noise, particularly in areas with frequent acceleration and deceleration. This involves installing dampers directly on the rails to absorb vibrational energy and reduce noise transmission. Optimizing train acceleration by improving traction motor control systems can also help minimize noise generation during these phases by ensuring smoother transitions and reducing mechanical stress on the components. High-frequency and high-intensity noise (Cluster 4 and Cluster 8) primarily originates from wind noise and track noise generated during high-speed travel, while the aerodynamic effects and wheel-rail friction may also exacerbate it. The implementation of noise control measures such as optimizing train and track design, utilizing seamless rails, and incorporating vibration reduction technologies are essential to minimize track vibration and noise. The application of vibration-dampening and sound insulation techniques, such as elastic pads and sound-absorbing materials at track crossings and switches, can notably reduce noise propagation. Additionally, regular rail grinding practices are also essential to effectively reduce wheel-rail contact noise, as illustrated in Figures 9 and 10. Regular rail grinding is important to maintain smooth wheel-rail contact surfaces, effectively reducing high-frequency noise caused by surface irregularities. This process involves precision grinding to remove surface irregularities and maintain a smooth rail profile, minimizing noise. Additionally, maintaining the quality of wheel treads is necessary, as it profoundly impacts wheel-rail noise, requiring regular inspections and resurfacing to ensure optimal contact surfaces. Figure 8: Noise control strategies for different intensity and frequency categories. Low-frequency and low-intensity noise (Cluster 5 and Cluster 7) primarily originates from the operational noise of the train at low speeds and the environmental noise encountered while passing through tunnels or over bridges. The tunnel reflection effect can produce noticeable low-frequency echoes, while the mitigation of these noises can be achieved by installing soundproof covers or panels on the air conditioning systems and electrical equipment within the train carriages. The adoption of low-noise designs for these systems and equipment, along with regular inspections and maintenance, can ensure their optimal operation and reduce noise generation. Additionally, the application of sound-absorbing materials such as acoustic panels and soundproof mats in tunnel and bridge areas can effectively reduce echoes and the reflection of environmental noise. Soundproofing the interior of the train carriages by installing acoustic panels and insulating materials can further reduce noise levels, especially when traversing enclosed spaces such as tunnels and bridges.