Abstract: A method for determining the longitudinal loading acting on a beam, such as a rail of a railway track subjected to longitudinal loading and, in particular, for determining the neutral temperature of railway tracks. The beam is energized longitudinally in the acoustic frequency range, and the level of magnetic Barkhausen noise at the surface of the energized region is measured. Measurements of the magnetic Barkhausen noise are taken for different longitudinal stress states and used for plotting the calibration curve of the magnetic Barkhausen noise as a function of longitudinal stress, the Barkhausen noise being measured at least at three points on the face of the built-in beam, and the calibration curve is used for determining the longitudinal loading on the cross-section in question using weighted averaging. The neutral temperature of the railway track is then calculated considering the modulus of elasticity, coefficient of thermal expansion and temperature of the rail.