The excellent Lifehacker sent me to the somewhat bizarre Buddha Machine Wall. This web site lets you blend short loops of "Buddhist temple music" together, making an ambient soundscape to cut out surrounding distractions. Although you'd think it would get repetitive and annoying, I've managed to play it for hours: it does shut out the surroundings, and in addition I don't even notice it after a few minutes. This is a lot better than my usual technique of listening to music, which does affect my concentration (though not as much as some of the noise going on in my office).
However, it does feel like a waste. When I listen to Spotify, getting to know new albums, I feel as if I'm doing something productive. Ironic, as all I'm doing is consuming, but there you are. Just listening to a wall of sound doesn't cut it.
It would have once, but I think my problem now is a continual feeling that I'm not processing information as fast as I should.
To help with this, I've started listening to podcasts and audio books at higher speeds. Both BeyondPod, my podcast app, and Audible both let you play at a variety of faster (or lower) speeds. I tend to stick between 1.25 and 1.5 times normal speed. Any faster than that and it's too easy to lose the thread. It doesn't work for music, unsurprisingly, and it's not very good for comedy,where timing is all important, but otherwise it works really well. Now the challenge is to train myself up to be able to listen at x2.