[square90]

The study examines a factory workplace which may already have a high-level of background noise. Perhaps the effect is non-linear? Anecdotally, two or three coworkers talking near me doesn't feel more distracting than one coworker on the phone.

[Sharlin]

Well, the dB scale is already deeply nonlinear. Adding a 50dB conversation to 40dB ambient noise results in… 50.4 dB total noise. Add two more people each talking at 50dB (at the same time!) and the total noise is about 55dB.