Building a New RAID

(Unrelated to my other recent RAID question) I am building a new RAID this morning, using 2 Seagate 160Gb SATA Hard Drives. I am getting a click/beep every 3 seconds, and it's making me kind of nervous. I had both drives tested using seagate seatools and both passed. I also had Spinrite 6 run on them. Between the utilities and building though, they were in the client's office for about a week and I'm hoping that nobody did anything stupid. It seems like if it were a hard drive having read troubles though that it would not be so steady. Having written that, the frequency just increased somewhat and then went back to normal. It almost sounds like a system temperature alarm except (SP?) quieter and the CPU Cooler fins don't feel very warm. Any ideas?