Change the notification sound for the Google Voice extension in Chrome
These instructions apply to Linux but can be applied to any operating system.
- Install apache2 and get it running 
sudo apt-get install apache2 - Copy your ringtone to the web folder 
cp ~/Downloads/my-ringtone.mp3 /var/www/ - Test it out by pointing your browser to the ringtone 
http://localhost/my-ringtone.mp3 - Find the real path of the Google Voice extension
    
- Open the extensions tab in Chrome
 - Copy the id from the Google Voice extension (mine is 
kcnhkahnjcbndmmehfkdnkjomaanaooo) - Use this ID to select the correct folder in the directory below
 
 - Edit the Google Voice extension itself to replace the default ringtone path with your own 
vim ~/.config/google-chrome/Default/Extensions/kcnhkahnjcbndmmehfkdnkjomaanaooo/2.3.6.8_0/background.html- Copy and paste the line labelled 
audio id - Comment out one of the copies in case these steps go horribly wrong
 - Replace the value of the src variable with the path to your ringtone 
http://localhost/files/my-ringtone.mp3 
 - Copy and paste the line labelled 
 - Go to the extension page and disable then enable the Google Voice extension to force a reload of the extension file you just edited Ba-da-boom ba-da-bing, you now can change the ringtone to whatever you want!