The structural intensity (STI) characterizes the energy flow in solid structures between an energy source and an energy sink. In numerical simulations the structural intensity can be calculated from internal forces and moments multiplied with vibrational velocities and angular velocities. These quantities can be computed by means of modal superposition. The accuracy of this method and thus the calculation of the STI strongly depends on the number of mode shapes considered in the harmonic simulation. The error of the STI related to the number of mode shapes considered in the calculation is studied by means of a convergence analysis,. For a good accuracy of the STI over a wide frequency range, several thousand mode shapes must be taken into account. The STI can be used to calculate the input or dissipated power of certain areas of the structure. This can be done by a numerical integration along a cyclic integral. In this paper, the influence of the distance between the integration path and the source (excitation point) or the sink on the calculation of the input or dissipated power is shown. An optimal distance for the integration path can be found that results in a minimal error
