Head into settings > lock screen and security > notifications and you can change the transparency of the lock screen notifications banner. (pocket-lint.com)
It's possible that disabling this option may also disable future notifications banners from OneDrive in File Explorer, but we haven't seen any notification messages from OneDrive yet. (howtogeek.com)
So, if you still want to see notification banners in the lower - right corner of the screen, but you find the notification sounds annoying, you can turn the sounds off without fearing that you might miss important notifications. (howtogeek.com)