Try "Brown Noise" if you have ADHD or problem at concentrating
Recently I had been struggling with concentrating on anything and scrolling on r/productivity subreddit. I have found about the brown noise.
I won't go into scientific explanation about what it is but it simply is a rumbling sound like a waterfall, a storm with a bass-like tone.
It helps you calm down and concentrate while working and studying; also lets you sleep better at nights.
I've been trying it for a couple of weeks and I can say that I'm better at concentrating at work. (i haven't tried it for sleeping yet)
There are also white and pink noises, too, but I haven't tried them yet. Each noise style is meant to be used for different usages, as far as I understand.
After reading lots of posts on reddit, I saw that it is quite popular especially among people with ADHD.
If you would like to give it a try, just search brown noise on youtube and you will see tons of results.