Why does the sound of the Xiaomi Robot Vacuum S40 get louder when cleaning?

If the sound of the Xiaomi Robot Vacuum S40 get louder when cleaning, please refer to the following steps:
1. Check if the brush is entangled with foreign objects and makes abnormal noises. Clean the brush in time, otherwise it will be damaged;
2. To ensure the cleaning effect, the robot vacuum uses a fan with greater suction power, which has a stronger dust collection effect and a relatively louder sound. When cleaning, you can use the quiet mode like Silent or Standard with less noise;
3. When the robot vacuum is working on smooth tile floors and wooden floors, the friction between the brush and the floor will produce a slight sound;
4. When the robot vacuum passes through the joints between tiles and floors, it will contact and clean the floor joints, which will produce a slight clicking sound.
Note:
The above sounds do not affect the normal use of the robot vacuum.