It's noticable from under the hood and somewhat from inside the car. It's not that annoying and it doesn't sound like anything is horribly wrong - but it's not a natural noise so I want to fix it. It definitley sounds like it's coming from the left side of the car. I was thinking maybe it was the ABS motor, but I don't know...

I also have a slight hissing nosise which sounds like a crack in a vacuum line, but I haven't been able to find that, either. That's audible when the car is running and then continues to make a hissing/bubbling sound when the car is shut off.

Between the two of these, I'm driving myself nuts trying to fix them both.