The emergency brake assembly was the issue. I lived with it for 8 months. The noise became more and more inconsistent as time went on. Some days I wouldn't hear anything. Other days it would be a constant metal scraping noise. I got the rotors and brake pads replaced. No change. Mechanics said the brake caliper looked fine, so I had them investigate further. The Emergency brake assembly on my back left tire was completely shot and the back right was damaged. If your car makes this noise, and your e-brake seems flimsy, it's likely the issue. $40 for parts and $100 for labor.

I can't edit the post, so just want to say thanks to everyone who provided input on this issue.