Some people can work even though they get interrupted and disturbed all day, others are very averse to being distracted and try to reach deep work or get in the zone. The problem with an open office is the first group.
The effect also depends on the type of work you are currently doing. Some work requires more concentration and is more easily disturbed. Other, more routine work, can tolerate more noise (be it audible or visual.)
I had been given a task by my manager, in such a way that my coworkers could hear that it was something important I had to get done ASAP.
Half an hour later, I'm heads down working, with earphones in. Very obviously coding. Coworker taps me on the shoulder. "Yes?" "Why aren't you chatting with us?"
I'd like to say I made some clever remark, but at the time I was speechless.
(Please note that I do engage in normal small talk at other times. )