To close oneself in an office with earplugs allows to concentrate better, but does not allow to think better. A little bit of noise is even preferable.
Ravi Mehta, professor in commerce at the University of Illinois, has studied the impact of ambient noise on creativity, and our brain’s capacity to think more abstractly when confronted to sound disturbance. Conclusion : the most stimulating sound level is around 70 decibels, which is about the sound level you’ll find in a neighborhood café.