When using the chat your visitors expect you to answer instantly, so it is essential that you can be notified when a new message arrives. Depending on your browser, we will either display a desktop notification (for recent browsers) or a simple pop-up and play a sound alert.
There are two types of visual alerts. The desktop notifications :
and the pop-ups :
If both are allowed, only the notifications will be displayed.
Click on the padlock on the left side of the url bar to check if they are allowed as well as the sound alert :