I have a 2003 Forester X, auto transmission with about 5500 miles. In the past 750 miles, I've noticed a sound the car makes as if there is a rock or metal object stuck in the tire tread. Beginning about 40 mph, a click, click, click sound is heard, and gets faster as the speed increases. I checked the tires for an object and found nothing unusual. What I find unusual is that the sound is only heard when the accelerator is pressed. If I'm coasting at speed, the sound disappears. When I pressed the gas again, the sound comes back. The pitch of the sound seems to change under different road surfaces (asphalt/concrete). I brought it to the dealer who said there were a lot of rocks in the tires, and I asked why the sound wouldn't be heard when coasting. They didn't know. When approaching speeds 65+, the sound almost sounds like a helicopter as the clicking gets faster. This sound is also intermittent and subtle. If the radio is on, the air is on high, or the windows are rolled down I don't hear it, which may be a reason why I just recently started to hear it. Any help? Is it just the sound of this car?