So I was tired of constantly checking my other computer which I mainly use for downloading, so I made this very lightweight Google Chrome extension called ‘Download Notify’. It gives you a single beep on completion of one download, and when all downloads are complete you get a final completed sound.
Check it out here: https://chrome.google.com/webstore/detail/download-notify/nieieojodgghoomakdkpkeipnncmbhdo?hl=en-US