Recently aquired a 2005 XC70 and love it! However, on a recent weekend drive it started making a noise that I can't pin down. Came off the highway into a small town and the first stop sign I came to, just as I stopped, I heard a low moan (less than two seconds), a pause then immediately another one of shorter duration. My wife described it as sounding like a distant fog horn. Then as I pulled away I began noticing a sound that seemed to be coming from the front of the car. At first we thought it could be a rattle then decided it was more like a low pitched rubbing sound. It wasn't anything that could be felt in any way, only heard. It was completely random in the sense that it wasn't affected by road conditions such as bumps. It wasn't really noticable above seventy or eighty kilometers per hour, only at slower speeds. The next day on the way to work, of course, it wouldn't do it so I couldn't get a tech to test drive it. Last night on the way home from work it did it again for the first time in a month. This morning on the way to work, no dice. Any input would be appreciated.