Hi, I recently bought a 2012 Scion xB because it’s been one of my favorite cars since I was a kid. I bought it with 80k miles and after a few weeks of it driving very smooth and well, I began hearing a weird noise at around 35-40 miles per hour or just around the 1500 rpm mark. It almost sounds like a light train horn and it begins to happen after driving it for a while. I brought it to my father who is a master mechanic for Nissan and we only found a caliper going bad and had it replaced to see if it was one of the tires dragging, but the noise still persists and we can’t figure out why. Sometimes it’s very loud and starts to vibrate under the front drivers side and sometimes it’s very subtle. It ONLY happens at 35-40 or 1500 rpm. It’s an automatic and I’ve looked every where to see if anybody else has solved this issue with no results. Any ideas before I take it to a shop and get possibly ripped off?