I know no one these days use FTP transfer but I still do. And this is something I am really annoyed at during transfers.

So if you are one of those people who want to get rid of this follow this.

On Windows 8 and above

1. Open Notifications and Settings by pressing the windows key.
2. Scroll down to Filezilla.
3. Click on it. Don't turn it off from there directly.
4. Inside it you will find an option to turn off the sounds.