Same here. For me it's people talking on the train. There's always just one person shouting into a cell phone, or some chatty office worker who wants to spend the entire hour unloading office politics on the person next to her.

Or worse, someone watching a television program on a tablet without wearing headphones.

And once I hear it, I can't think about anything except for what they're saying and how much I want to murder them.

Fortunately I found a decent pair of $20 earbuds. They've lasted a year and work well enough, and they'll be cheap to replace when they fail. I use a white noise generator app called "My Noise" to drown out the background. It's kind of strange but I just don't feel the need to listen to music or podcasts anymore; I just want an hour of silence!

Glad to hear the new job is working out!