Q: Rattling noise from under the car

On my Suzuki Esteem, both outer CV boots are torn. I don't know how long they've been torn because I acquired the car recently and they were already torn. It doesn't make any clicking noises when I turn. The inner boots are OK. However, I occasionally get a low pitched rattling sound from under the car. It sounds like perhaps something's loose. It doesn't seem to affect the way the car drives but it freaks me out. This sounds happens from time to time and is not regular. I can go days without the sound, then it starts up again and vanishes after a while. I checked the tie rods, brakes, and struts and they all seem well. I thought it was the axles that were bad due to the torn boots but there's no clicking sound, even when I do radical turns. What do you suggest I check next? Could the sound be due to the torn CV boots?

My car has 90000 miles.
My car has an automatic transmission.