A multilayer structure comprising: - a layer α1; - a porous fibrous layer α2 comprising: (i) a fibrous felt material selected from the group consisting of a fiber mixture composition of a synthetic fiber and a glass fiber, a fiber mixture composition of a synthetic fiber and a natural fiber; a natural fiber, being said fibrous felt material in amount of at most 70% by weight of the total weight of the porous fibrous layer; and (ii) a phenolic thermosetting resin in amount of at most 30% by weight of the total weight of the porous fibrous layer; - a porous-cellular layer β comprising a semirigid, thermoformable polyurethane foam obtainable by a polyether and diphenylmethane diisocyanate; and - a layer γ, wherein the elastic modulus E according to UNI EN ISO 527 of said structure is proportional to the value of the following formula : ∑ 1 n SW 2 t max 2 λ ∗ π 3 α 500 Hz ∗ α 1000 Hz ∗ α 4000 Hz wherein SW is the superficial weight (g/m 2 ) of each layer; n is the number of layers in structure; α is the sound absorption coefficient, for normal angle wave incidence, at specified frequency according to UNI EN ISO 10534; t max is the maximum final thickness of the structure; and λ is the total thermal conductivity according to UNI EN ISO 8301, being the elastic modulus E measured according to UNI EN ISO 527. - a layer α1; - a porous fibrous layer α2 comprising: (i) a fibrous felt material selected from the group consisting of a fiber mixture composition of a synthetic fiber and a glass fiber, a fiber mixture composition of a synthetic fiber and a natural fiber; a natural fiber, being said fibrous felt material in amount of at most 70% by weight of the total weight of the porous fibrous layer; and (ii) a phenolic thermosetting resin in amount of at most 30% by weight of the total weight of the porous fibrous layer; (i) a fibrous felt material selected from the group consisting of a fiber mixture composition of a synthetic fiber and a glass fiber, a fiber mixture composition of a synthetic fiber and a natural fiber; a natural fiber, being said fibrous felt material in amount of at most 70% by weight of the total weight of the porous fibrous layer; and (ii) a phenolic thermosetting resin in amount of at most 30% by weight of the total weight of the porous fibrous layer; - a porous-cellular layer β comprising a semirigid, thermoformable polyurethane foam obtainable by a polyether and diphenylmethane diisocyanate; and - a layer γ, wherein the elastic modulus E according to UNI EN ISO 527 of said structure is proportional to the value of the following formula : ∑ 1 n SW 2 t max 2 λ ∗ π 3 α 500 Hz ∗ α 1000 Hz ∗ α 4000 Hz wherein SW is the superficial weight (g/m 2 ) of each layer; n is the number of layers in structure; α is the sound absorption coefficient, for normal angle wave incidence, at specified frequency according to UNI EN ISO 10534; t max is the maximum final thickness of the structure; and λ is the total thermal conductivity according to UNI EN ISO 8301, being the elastic modulus E measured according to UNI EN ISO 527. SW is the superficial weight (g/m 2 ) of each layer; n is the number of layers in structure; α is the sound absorption coefficient, for normal angle wave incidence, at specified frequency according to UNI EN ISO 10534; t max is the maximum final thickness of the structure; and λ is the total thermal conductivity according to UNI EN ISO 8301, being the elastic modulus E measured according to UNI EN ISO 527. <EOS>