…it’s really cool. Try it and see!
Hardware pink noise generator + speaker + leave it on all day while you’re working.
Note my setup also includes a 10 turn 5′ diameter coil (around my desk chair) in series with the speaker from another experiment. I don’t think this is part of the effect. It also appeared (in a very much attenuated and distorted form) with pink noise into the Neurophone.
Overall the effect decreases slightly with a high-volume pink noise source and increases with a quiet and/or far-away one.
Also worth noting is it wasn’t until many days (weeks?) after setting up the pink noise + speaker that any effect was apparent. But the productivity boost from adding the pink noise + speaker was itself more than worth it.
And it was dirt cheap!
I think I put less than 15 Euro worth of parts into it (the speaker was repurposed from a computer speaker setup). It looks like Velleman sells pink noise generator kits for $20 (available online).
(In terms of improved productivity it’s already earned the parts cost back, several times over.)
For those with money to burn there’s always the Marpac Dohm-DS / 980 for $50, which is an even better way to go as it’s pure-mechanical. But hard to find and hey, DIY is cooler.