Open plan offices became standard across American workplaces over several decades. The reasons were architectural and financial, and the consequences for concentration follow from what the layout removes.
The layout was chosen for cost per person
Removing walls increases the number of people a floor can hold, and real estate is typically among the largest fixed costs an employer carries.
Open floors are also cheaper to reconfigure when teams change, which matters to organizations that restructure frequently and want to avoid construction.
Collaboration was the public justification, but the durable driver has been density and flexibility, which is why the layout persisted through years of complaints.
Speech is the specific problem
Background noise is tolerable when it is steady, and people work through ventilation hum without difficulty because it carries no information.
Intelligible speech is different, since language is processed involuntarily and competes with the verbal thinking required for reading, writing and calculation.
This is why a nearby conversation disrupts more than louder machinery, and why headphones playing music with lyrics only partly help.
Visibility changes behavior
Working within sight of others introduces continuous low-level self-presentation, since posture, screen content and time away from the desk are all observable.
People respond by appearing occupied, which favors visibly active work such as messaging over the stationary concentration that looks like doing nothing.
Employers frequently observe increased digital communication after moving to open floors, which is consistent with people retreating from face-to-face interruption into channels they control.
Interruption costs land later
A brief question costs more than the seconds it takes, because returning to an interrupted task requires rebuilding the mental state that supported it.
Since that cost is paid after the interrupter has left, it is invisible to them and easy to underestimate on both sides.
Accumulated across a day of open-floor interruptions, the rebuilding time becomes a substantial share of the hours nominally available for focused work.
What mitigations actually address
Effective responses give control back, including bookable quiet rooms, agreed focus hours, and norms about messaging rather than approaching a desk.
Sound masking helps by reducing speech intelligibility rather than by lowering volume, which is why it sounds like adding noise and still works.
Individual coping practices are limited here, because the constraint is environmental, and workers who find concentration persistently impossible have a workplace problem rather than a personal deficiency.