In a 2014 study conducted by researchers from the University of Gävle in Sweden, participants were asked to write short essays under five different acoustic conditions. Background noise in the five conditions ranged from 0.08 to 0.71 on a measure called the Speech Transmission Index—that is, from completely unintelligible speech, to somewhat intelligible speech, to crystal-clear speech. The participants’ writing fluency, the investigators reported, dropped “drastically” at Speech Transmission Index values above 0.23—levels that, they note, “would not be at all uncommon” in an open-plan office.
