Generator set comprising: - an internal combustion engine for generating mechanical energy from the combustion of a fuel, - an alternator for converting the mechanical energy generated by the internal combustion engine into electrical energy, - a switchboard electrically connected to the alternator to control and distribute the electrical energy generated by the alternator, - a casing comprising a bottom wall and at least one lateral wall (10, 11), which define a compartment that houses the internal combustion engine and the alternator; said bottom wall and said at least one lateral wall (10, 11) comprising an internal surface directed towards the compartment of the casing; said casing comprising slots obtained in said at least one lateral wall (10, 11) in order to put the compartment in communication with the exterior; - first set of partitions made of sound-absorbing material, which are disposed in spaced arrangement inside the compartment of the casing near the slots; wherein the partitions of said at least one set of partitions are disposed in orthogonal direction relative to said at least one lateral wall (10, 11) of the casing provided with said slots, and are disposed in adjacent parallel position in such a way that a gap is generated between two adjacent partitions, said gap receiving the air sucked from the exterior through said slots, wherein said internal surface of said bottom wall and of said at least one lateral wall (10, 11) of the casing is covered with sound-absorbing panels, characterized in that said sound-absorbing panels have a thickness higher than or equal to 6 cm, and the generator set further comprises - a second set of partitions made of sound-absorbing material, which are disposed inside the compartment of the casing, in proximal rear position relative to the first set of partitions according to a forward traveling direction of the air that is conveyed inside the compartment of the casing, said second set of partitions being in orthogonal direction relative to said at least one lateral wall (10, 11) of the casing provided with said slots and said second set of partitions being staggered with respect to said first set of partitions. - an internal combustion engine for generating mechanical energy from the combustion of a fuel, - an alternator for converting the mechanical energy generated by the internal combustion engine into electrical energy, - a switchboard electrically connected to the alternator to control and distribute the electrical energy generated by the alternator, - a casing comprising a bottom wall and at least one lateral wall (10, 11), which define a compartment that houses the internal combustion engine and the alternator; said bottom wall and said at least one lateral wall (10, 11) comprising an internal surface directed towards the compartment of the casing; said casing comprising slots obtained in said at least one lateral wall (10, 11) in order to put the compartment in communication with the exterior; - first set of partitions made of sound-absorbing material, which are disposed in spaced arrangement inside the compartment of the casing near the slots; wherein the partitions of said at least one set of partitions are disposed in orthogonal direction relative to said at least one lateral wall (10, 11) of the casing provided with said slots, and are disposed in adjacent parallel position in such a way that a gap is generated between two adjacent partitions, said gap receiving the air sucked from the exterior through said slots, wherein said internal surface of said bottom wall and of said at least one lateral wall (10, 11) of the casing is covered with sound-absorbing panels, characterized in that said sound-absorbing panels have a thickness higher than or equal to 6 cm, and the generator set further comprises wherein said internal surface of said bottom wall and of said at least one lateral wall (10, 11) of the casing is covered with sound-absorbing panels, characterized in that said sound-absorbing panels have a thickness higher than or equal to 6 cm, and the generator set further comprises - a second set of partitions made of sound-absorbing material, which are disposed inside the compartment of the casing, in proximal rear position relative to the first set of partitions according to a forward traveling direction of the air that is conveyed inside the compartment of the casing, said second set of partitions being in orthogonal direction relative to said at least one lateral wall (10, 11) of the casing provided with said slots and said second set of partitions being staggered with respect to said first set of partitions. said second set of partitions being in orthogonal direction relative to said at least one lateral wall (10, 11) of the casing provided with said slots and said second set of partitions being staggered with respect to said first set of partitions.