When you connect to the charger, your device emits a notification sound to let you know that the phone is connected to the charger.
Charging sound for Samsung Galaxy Note 8 as per the following instructions:
Step 1: Firstly, navigate to Sound and Vibration settings.

Adjusting Sound and Vibration
Step 2: Here, you can toggle the sound of charging on or off as needed.

Turn on Charging Sound
This will silence the charging connection sound. Wishing you success.