The Agricola Online website has 3 types of alerts.
(1) ALERT ME (when players wanted) : This feature is activated from inside the main room. It will make your computer ring when a game is created and players are needed to join.
(2) [Ctrls]-->"Turn Alert On" : This feature is turned on from inside game board. (A) It will make your computer beep when it is your turn to place your farmer and (B) It also beeps as each player finishes their turn.
(3) /ping name message: If a player wants to get another player's attention, then they type this into any chat window. The named player (who must be in the same room as you) will hear a bell sound on their computer and see the name of the person requesting their attention along with the message. The message can be left blank.

In order for sound to work on the Agricola Online website, you must hear sounds when you push the buttons below. If you do not, (1) Install and enable the Java plugin. (get it at http://java.com) (2) Make sure your computer speakers are turned on.