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In this work, the viscoelastic behavior of open cell polyurethane foams used in noise control applications is investigated through dynamic mechanical analysis in compression. Several levels of static strains superimposed on a small dynamic one were considered in order to assess the effect of material non-linearity on the mechanical response. Further, a wide range of frequencies and temperatures was explored. For each static strain a different master curve for conservative component of complex modulus, E’, could be determined. Interestingly, the loss factor was the same at all static strains, indicating that the relative contribution of energy dissipation and conservation is unaffected by the static strain. Moreover, shift factors (and thus the bulk material relaxation times) turned out to be independent on static strain level. These results suggest that the non-linearity of the foam is linked to the change in foam structure with strain rather than to a non-linear behavior of the viscoelastic constituent m...