So, for the past 7 weeks or so.. My Mac pro 2.93 Octo-Core has been making the sound from the movie "Sunshine" where the ship is pinging a distress signal , it's a rather alien sound and it's driving me INSANE. It only happens when their is no input to my speakers, in example.. if i'm watching a movie or have itunes open playing music, it doesn't happen. However when it's idle it will make this same sound over and over in perfect repetition and time. the sound last for 3 seconds, then is silent for 2 seconds, then it's back again.. over and over.. I've tried different speakers, headphones.. you name it. it's got to be the sound card. I have apple care, but I work daily for a living with this machine and cant afford the time spent sending this machine away for a replacement part. Any suggestions? I'm thinking about recording this sound and posting it here so you all can hear it and imagine hearing it several hundred times a day.