Scraping sounds under the car

I first noticed the scraping sounds when I was driving on 128 (it was intermittent lasting a couple of minutes) I thought at first it was related to going over bumps in the road but the second time I drove it on 128 I had driven 30 miles before it started again and this time it lasted 15 minutes or so. I’m not good at describing sounds but it sounds like metal scraping. When I got off the highway I could still hear the sound but not as loudly.