Pleasant, configurable background noise in your browser... It's free, and it's pretty darned good: Noisli. It's been running on my system for about a week now. If I'm writing code, or writing prose, it's a better background sound than even instrumental music.
Right now I'm listening to a mix of forest sounds, a gently burbling stream, and a distant thunderstorm. Lovely. One of the options for background noise is the sounds of a busy cafe. I can't imagine anything worse for me. I'd be willing to bet you that there is a strong correlation between extroversion and the selection of that sound as a background :)