This　paper　presents　an　exact　elasticity　model　for　a　fluid-loaded　periodically　rib-stiffened　plate　covered　by　a　decoupling　acoustic　coating　layer,　which　is　built　upon　the　plain　strain　elasticity　theory.　The　acoustical　coating　layer　is　assumed　to　be　perfectly　bonded　to　the　parallelly　rib-stiffened　plate,　which　is　impinged　by　a　time-harmonic　plane　sound　wave.　The　theoretical　model　begins　with　Navier-Cauchy　equations　of　motion　to　describe　the　vibration　behavior　of　the　rib-stiffened　plate　and　the　acoustic　coating　layer,　and　utilizes　the　acoustic　equation　to　model　the　fluid　motion.　Applying　the　continuities　of　displacements　and　stresses　at　the　interfaces　of　the　plate,　the　coating　layer　and　the　fluid　mediums,　the　vibroacoustic　governing　equation　can　be　solved　to　obtain　the　sound　transmission　loss　(STL)　of　the　structure.　The　plane　strain　model　is　verified　by　comparing　with　the　thin-plate　model,　and　good　agreements　have　been　achieved　between　the　two　predictions.　Based　upon　the　theoretical　model,　the　influences　of　the　geometrical　parameters　of　the　structure,　sound　incidence　angle,　the　dilatation　and　shear　wave　speeds　in　the　acoustic　coating　layer　on　the　STL　of　the　structure　are　numerically　explored.　Results　reveal　the　significant　effect　of　the　decoupling　acoustic　coating　layer　on　the　noise　reduction　of　the　periodically　rib-stiffened　structures.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.