A burner, comprising: - a support wall forming an inlet passage for introducing a mixture of fuel gas and oxidant into the burner, - a diffuser wall, which is tubular and coaxial with respect to a longitudinal axis of the burner and having a first end connected to the support wall in flow communication with the inlet passage, a second end closed by a closing wall, and a perforation for the passage of the gas mixture from the interior of the burner to an outer side of the diffuser wall, where the combustion occurs, - a first diaphragm with one or more first through openings and a second diaphragm with one or more second through openings, said first and second diaphragms being substantially concentric with the longitudinal axis and arranged in sequence in the inlet passage, so that the mixture passes first through the one or more first openings of the first diaphragm and next the one or more second openings of the second diaphragm, wherein each of the first and second diaphragms (12, 14) form a radially inner circular portion (16, 16') having a radial width (Ri) and a directly bordering radially outer annular portion (17, 17'), respectively, wherein: - the radially outermost extent of said one or more first openings defines an outer radius (Re) of the outer portions (17, 17'), - the ratio (Ri/Re) between the radial width (Ri) of the inner portion (16, 16') and the outer radius (Re) of the outer portion (17, 17') ranges between 0.6 and 0.7, preferably about 0.65, - in the radially outer portions (17, 17'), the sum of the passage area of said one or more first openings is larger than the sum of the passage area of said one or more second openings, - in the radially inner portions (16, 16'), the sum of the passage area of said one or more second openings is larger than the sum of the passage area of said one or more first openings, characterized in that - the free axial distance between the first diaphragm and the second diaphragm ranges between 0.22*Re and 0.43*Re, preferably about 0.31*Re, wherein Re is the outer radius (Re) of the outer portions (17,17'), wherein the first through openings further comprise a central hole concentric with the longitudinal axis and having a passage area that is less than both the total passage area of the first through openings in the radially outer portion of the first diaphragm, and the total passage area of the second through openings in the radially inner portion of the second diaphragm, wherein the first through openings comprise a group of peripheral openings having a "T" shape and arranged in a circumferential sequence with respect to the longitudinal axis, wherein each of the peripheral openings forms a substantially rectilinear portion, oriented in the radial direction with respect to the longitudinal axis, and a tangent portion extending substantially in the circumferential direction with respect to the longitudinal axis. - a support wall forming an inlet passage for introducing a mixture of fuel gas and oxidant into the burner, - a diffuser wall, which is tubular and coaxial with respect to a longitudinal axis of the burner and having a first end connected to the support wall in flow communication with the inlet passage, a second end closed by a closing wall, and a perforation for the passage of the gas mixture from the interior of the burner to an outer side of the diffuser wall, where the combustion occurs, - a first diaphragm with one or more first through openings and a second diaphragm with one or more second through openings, - the radially outermost extent of said one or more first openings defines an outer radius (Re) of the outer portions (17, 17'), - the ratio (Ri/Re) between the radial width (Ri) of the inner portion (16, 16') and the outer radius (Re) of the outer portion (17, 17') ranges between 0.6 and 0.7, preferably about 0.65, - in the radially outer portions (17, 17'), the sum of the passage area of said one or more first openings is larger than the sum of the passage area of said one or more second openings, - in the radially inner portions (16, 16'), the sum of the passage area of said one or more second openings is larger than the sum of the passage area of said one or more first openings, characterized in that - the free axial distance between the first diaphragm and the second diaphragm ranges between 0.22*Re and 0.43*Re, preferably about 0.31*Re, wherein Re is the outer radius (Re) of the outer portions (17,17'),