There's a sneaky menu bar background noise app already built into MacOS. You can add "Hearing" to the menu bar (or control center) from settings, and then use that to enable "Background Sounds"
I can’t quite tell if Apple putting handy utilities (e.g. white noise) and options (e.g. reduce motion) within Accessibility settings, along with controls for braille readers and joystick controls, is part of a universal provision initiative (i.e. reducing stigma in having to use Accessibility settings).
Note: Generally "dark" (as opposed to "bright") means emphasis on the lower frequencies, which is a good description for brown noise, but they aren't formally the same. Formally, brown noise refers to a power distribution that drops ~6 dB per octave, and I have no idea how strictly apple's "dark noise" matches the technical specifications of that.
Is "Dark noise" the equivalent of "Brown noise"?
Note: Generally "dark" (as opposed to "bright") means emphasis on the lower frequencies, which is a good description for brown noise, but they aren't formally the same. Formally, brown noise refers to a power distribution that drops ~6 dB per octave, and I have no idea how strictly apple's "dark noise" matches the technical specifications of that.
I generally listen to white noise when I am trying to concentrate, but its Dave Clarke's techno/electo podcast, "White Noise"! https://www.youtube.com/watch?v=36FkrrpzFOA