A new approach of marine vibration problems is given, showing that for modern, high powered ships excessive hull vibrations at service r.p.m. cannot be explained by hull resonances. The fundamental cause is the increased power. Therefore the solution of present-day vibration problems must be found in reducing the excitation forces, strongly dominated by propeller cavitation propeller shaft resonances. Calculation of hull vibrations is nowadays only required to know the final response level, in order to detect unpleasant or dangerous vibrations, and no longer to know the higher node hull resonances in order to avoid their excitation at service speed.