I am a new mac user and a sound similar to the "Frog" sound effect keeps playing at random times and with no apparent reason. It just plays and at different times...Sometimes it's every 20 seconds, sometimes more or less. I disabled the sound in System Preferences and it kept playing. I don't know what else to do since i'm new with mac... It's sounding right now, and the only application i have open is safari obviously, and the battery is charging. Help me please!