This hasn't happened before. My Mac (MacBook running OS 10.5.6) will flash instead of a "bloop" noise when I get a notification. When I get an alert, I won't get a noise anymore. Or when I hit a button on my keyboard that does nothing my computer won't make a noise. Now my displays just flash white for a second. I have no idea how this happened. Can someone help me because this is really bothering me.