I have a new 2007 Chevy Trailblazer - less than 400 miles. Driving on the highway yesterday and, then again today noticed a district, mid level high pitched "ringing" sound coming from the driver side front tire (left front) - only this wheel. It starts within 5-10 minutes of driving, and stops only when the car stops (i.e., applying the brakes does not stop it, and it is there at all speeds. Reading the handbook, there is a sound refernced in relation to brake wear indicators, but it would be strange for that to be happening on a car that is brand spanking new. Nothing unusual has happned with the car and no bad weather driving has taken place. Any ideas what this could be? Thank you