Receiving audible notifications when alarms are triggered is now possible thanks to the Monitoring section of the Ajax Pro Desktop PC software. It is located in the initial tab of the program (before selecting any Hub) and, when you click on its tab, another window opens with a notification log and all kinds of information (event, comments, hub, user...).
To receive the sound notification, we simply have to open that tab and, if we want, leave it in the background because when an alarm goes off the window will pop-up and sound siren type. It looks like this: