The problem of noise transmission through a structure into a cavity appears in many practical applications, especially in the automotive, aeronautic and space industries. In the mean time, there is a trend towards an increasing use of composite materials to reduce the weight of the structures. Since these materials usually offer poor sound insulation properties, it is necessary to add noise control treatments. They usually involve poroelastic materials, such as foams or mineral wools, whose behaviour depends on many parameters. Some of these parameters may vary in rather broad ranges, either because of measurement uncertainties or because their values have not been fixed yet in the design process. In order to efficiently design sound protections, performing a sensitivity analysis can be interesting to identify which parameters have the most influence on the relevant vibroacoustic indicators and concentrate the design effort on them. The Fourier Analysis Sensitivity Test (FAST) is used in this work to study the effect of several design parameters on industrially relevant quantities such as transmission loss and noise reduction index. Two configurations are studied : The first one is an academic example of sound transmission through a layered composite plate, calculated with an analytical model based on the transfer matrix method. The second is a Statistical Energy Analysis (SEA) model of an industrial case featuring a higher degree of complexity.