Sound when brake Hyundai Accent 2014

There is a slight sound when I press on my brakes. It's not a sharp or squeaky sound but is rather a consistent low tone sound. I started noticing it a couple of days ago after I drove the back wheels through a pile of dirt that touched the undercarriage. I am not sure whether that is related, but I am wondering whether there might be dirty stuck in the brake pads that could be causing this sound.

I would be grateful if anyone has any insight about this.