I own an 03 Forester, and recently, whenever I press the brake, I have heard a noise that sounds like chattering coming from the front left of the car. I haven't heard the noise before, and I think it's the ASB system, because it doesn't sound like the usual brake problems - worn pads or warped rotor. I am unsure why I am hearing this noise and if the noise indicates a bigger problem. The ASB light has not illuminated. Any ideas? I am new to soobs, so any help would be appreciated. Also, can anyone recommend a good independent Subaru mechanic in Southern California?

It's hard to diagnose a problem involving noises and symptoms on the internet, but you could do some testing before you go to the shop. Usually the ABS is pretty apparent when it engages, you feel it in the petal and can hear the ABS pump run. If you can find an appropriate place to test it (when there is no traffic or large objects, etc), find dirt, gravel or a wet surface and hit them hard from about 10-15 MPH. that would give you a comparison to see if it's the same noise you hear. Ordinarily the ABS wouldn't make noises or activate by normal brake usage every time you apply the brakes.