The effect of noise on focus and productivity is super-interesting and one that I've only accidentally come to realise recently myself. I live in an averagely noisy part of the city and built myself a room-within-a-room sound-isolated studio as a fair chunk of my work is audio-related. I was quite surprised by how much my focus has increased since starting to work in the studio (even on completely unrelated work). Since then I've noticed how easily my focus switches at even the slightest noise (the fridge compressor kicking in, a car driving past etc)