Galaxy S6 edge+: Why is there noise when using wireless charger pad?
While charging the device, the fan inside the wireless charger will activate to cool the charger.
On this process, you may hear a slight sound however this is intended concept to prevent charger overheating and normal operation.
You can reduce noise by deactivating the fan.
To deactivate, open the Apps screen, tap Settings → Accessory, and then tap the Fast wireless charging switch to deactivate it. Please note turning off the fan will result in a slower charging speed.