Your application setting for notification type may be configured to "Alert Window." Change this setting by locating the Voom icon  in your system tray/dock, and right clicking it. Then select "Settings," and change "Use the following notification for alerts:" to "Tray Notification" and click "Save."

If you want to disable the timer function of Voom: Right click the Voom icon  in the system tray/dock and click "Timer Running" if it has a checkmark next to it. Then, right click the icon  again, and click "Settings." In the settings window, uncheck "Begin timer on startup" and click "Save."