Buzzing noise - 2004 CTS
 

Hi, I just purchased a 2004 CTS with sport package, 113k miles. Once every 2 or 3 minutes, I hear a buzzing noise coming from around the vicinity of the front passenger wheel, although I suppose it could also be coming from in the engine compartment. It happens for about 1 or 2 seconds, often less, and stops. The best way I can describe the sound is when you have fan, and the blades of the fan hit the cage. I understand it's a long-shot that anyone would know this based on a description of a sound, but if it's something really common, maybe someone has experienced this before. Any ideas?