Study of MAYDAY and S.O.S. as Radiotelephony Distress Signals
Keith K. Neely · The Journal of the Acoustical Society of America · 1956
MAYDAY and S.O.S. were compared in the presence of noise and speech to determine their relative detectability values (audibility thresholds). Results of the tests indicated that S.O.S. had the lower audibility threshold and therefore the greater detectability value.