"We've had talk of grey-noise trials in our office -"
This is actually a well known Contact Centre technique.
Noise volumes in a "quiet" office soon escalate, as people get distracted by the people talking next to them, so raise their voice a little more in order to zone in on their conversation...then the people around them raise theirs. Rinse and repeat.
By introducing a base level sound, you are less distracted by other peoples conversations, and so so you tend not to raise your own voice.
So ironically, having noise introduced at a set level actually reduces overall noise in the environment.