"This study does not rank which masks are most/least effective. The authors clearly laid this out multiple times in the original study:"Again, we want to note that the mask tests performed here (one speaker for all masks and four speakers for selected masks) should serve only as a demonstration. Inter-subject variations are to be expected, for example due to difference in physiology, mask fit, head position, speech pattern, and such."The authors were in the Physics department and were just trying to create a cheap and easy methodology that could be used to analyze masks. They haven't actually done the analyzation."