Turbulences and vibrations can cause disturbing vibrational noises to ductwork. In order to avoid these noises, the best possible damping and stiffening of the ductwork is required. Rectangular straight ducts with unfavourable duct cross-sections, with high positive or negative pressure and, of course, in case of large duct cross sections do need reinforcement measures.Ventilation ducts with a large cross-section and varying excess pressure and negative pressure should be optimally stiffened in order to ensure maximum stability and elimination of flutter. The additional reinforcements then ensure that the duct sections remain dimensionally stable and that the entire ventilation system can be operated smoothly without pressure losses/leaks and, above all, safely.Gebhardt-Stahl reinforcement materials are easy to use and cost-effective.