This used to be a problem when I started working at a company in 2009. Lots of office noises and conversations going on, I couldn't focus. Pretty sure I have an oversensitivity to noise too, as mentioned in this article.
The solution for me was buying a (not cheap) pair of Bose QC15 noise-canceling headphones. One of the best decisions I've ever made.
That worked? I had to deal with conversations happening near my office a while back, and looked into noise-canceling headphones, but the reviews and articles I read claimed that they didn't do a good job on voice. They were designed for the kind of continuous noise you get from things like airplane engines, not for sporadic things.
I use QC-15 Bose headphones daily. You have to be listening to music (or your favorite white/pink/etc noise) while wearing them to be effective blocking voices nearby, don't believe anyone that tells you otherwise.
The paradoxical effect is that since they are effective blocking low frequency noises, the voices kind of stand up if not listening to anything.
for $20 I think it's a good investment and worth a try. I made two of these, one to have at home, other at work and even took them on airplane traveling.
Yeah. It worked so well that people would have to turn my office light on or off in order to get my attention, I'd really get in the zone and without external noise I would hardly notice people walking around.
The solution for me was buying a (not cheap) pair of Bose QC15 noise-canceling headphones. One of the best decisions I've ever made.