For me that means absolute silence (which means I can't ever get any work done in an open office). In these covid times I've rented a small private office very close to the house where I can hole up and concentrate (I have a younger child so silence isn't happening at home).
I turn off all notifications from every possible source. No emails, no slack, no phone. (My phone is always 100% on mute for everything, except calls from my wife in case there's an emergency).
Maybe most importantly, I take 20-30 minutes in the evening to make a plan on what to work on the next day. In the morning I just work on what I pre-planned. I will not check email or slack or anything at all until I've done 3-4 hours of solid work. Only then I'll check email in case there's anything new to care about. As soon as I check these communications the day tends to go downhill on distractions from dozens of discussion threads so I won't get anything else done in the day. But I banked in those 3-4 hours in the morning on progress.
When times are slow, sure, I'll check email/slack in the morning and won't get anything done all day.