Hi All. Proud owner of a 2015 XLE currently with 24,100 miles on it.Recently I've been hearing a slight whistle noise when applying the brakes steadily. The brake pads look fine, and I was wondering if anyone can shed some light on what this could be. Could it be dirt? I've purchased it at 19,000 miles. I have a scheduled oil change and full inspection coming up, but this noise is really bothering me. Any similar occurrences? What could it be?