Heard a train in background while on a Canon support site

I was researching some settings on a Canon printer website and all of a sudden I started hearing a train in the background. I was not watching videos, just reading. This was a steady, live sound of a train track including occasional whistle blows and even some car horns being sounded. It was like someone had hacked me and left a mic on by mistake. I left Safari and went to my home page and the sound continued. It sounded like someone was in a warehouse somewhere with a noisy background. I finally did a hard restart of my iPad and it quit. I bought this iPad new so I know it has not been jailbreaked. I get the usual spam emails but NEVER click on anything unsolicited. Straight to Trash.

Any ideas what I was hearing and why?