According to David, what is the main problem for staff using computers now?

W: I’d like to welcome David Whitesman to the program today. Good morning, David.
W: We’ve all turned our offices into open-plan areas and now people complain about the noise.
M: Quite rightly, I think. Listening to other people’s phone conversations is no fun. Although people spend a lot more time in meetings, their main occupation is what I call quiet work which is individual work and they need somewhere to do this.
W: Does this mean returning to offices with walls?
M: No, I think open-plan offices have a function. But we need to adapt: have a number of different styles of office in one place so that the staff could select somewhere peaceful when they need it.
W: Well, thank you, David Whitesman and that report.