I wish that worked. I'm in an open plan office where I constantly need the headphone to drown out the noise all the other things happening (people talking to each other, marketing people making phone calls, people walking about, etc) so that'd mean I'd be constantly unapproachable. I'd actually like that, but I'm pretty sure my co-workers and employer wouldn't.

A friend works in an office where headphones are even banned because they create too much of a barrier to talk to a co-worker. I'd go absolutely crazy there in less than a week.

What if I don't want to be distracted by everything around me, but don't mind being interrupted if there is something they are wondering about? Then I might have to wear headphones with the usual volume, 'cause if I wear it half-way or something then I still get a bit distracted by everything around me.

It's like leaving your door halfway open to signal that someone can come in if they want. I might not mind having a visit, but I might mind hearing all the noise, or curious looks from people passing by through the corridor. Hence the 'busy' sign to hang on the doorknob, when needed.

I don't quite catch what he's doing in the middle frames?