i find it difficult to focus sometimes due to the constant screaming voice in my head. i've found that brown noise is the only thing that drowns the voices out. i truly feel "no thought, head empty" when i listen to it through my noise canceling headphones. you can find 8-hour or 10-hour long brown noise videos on youtube.
iPhone (and now Mac) let's you turn on what it calls "Background Sounds" and has a selection of nature sounds, white/brown noise. The Background Sound volume can be adjusted independently of other sound sources too. So when I'm in a very loud environment or need to really block out the world, I turn on ANC, play some music, and slap on the sound of rain at 50%. I become sonically bulletproof.
