How to disable Notification Sounds and System Sounds on iPhone?

To disable System sounds:
Go to Settings > Sounds & Haptics
•    disable Keyboard feedback
•    disable Lock Sound
•    You can also customize other sounds in the Sounds & Haptics menu. Select each sound type (such as Text Tone, New Mail, Calendar Alerts, etc.) and set them to “None.”

To turn off notifications for selected applications:
Go to Settings > Notifications
1.    Select the app from the list for which you want to disable notifications. 
2.    Select “Sounds” and set it to “None”
Repeat for any applicable app.