I would recommend against sound cancelling headphones. The thing is that they only block out constant background hum like a fan. They don't stop talking.

What does stop talking though is a set of headphones call the 'Oppo pm-3'. These ones are like earmuffs, they have foam padding built-in, and the sound quality is pretty decent too.

Unfortunately I only discovered these 3 weeks after I burnt out of my open plan job and quit.