When I have to focus I usually listen to Desert/Stoner rock (strictly instrumental). One of my friends who is more into electronic music prefers minimal techno for the same reasons. Active noise filtering works best if there is some sound in your headphones.
If music absolutely bothers you, there are whitenoises on YT. My favorite is "10 Hours Of Relaxing Planet Earth II Island Sounds - Earth Unplugged", but if that is still too concrete there is my other favorite "CELESTIAL WHITE NOISE | Sleep Better, Reduce Stress, Calm Your Mind, Improve Focus | 10 Hour Ambient".