Asking people to reduce the noise level is straight up a horrible idea. Especially the obnoxious /noisy command and the nanny state thinking it encourages.
I thrive and get in the zone when there is plenty of noise and varied conversation around me. I know that many people feel the same way. A quiet office is the worst for maintaining focus, as then any little conversation will stand out and catch my attention.
And I say all this not as a loud person. Quite the opposite.
I almost never use headphones; don't need to because the office is noisy enough to stay in a good coding zone. But having some social stigma about wearing them, that would be bad.