Resonant device, such as a striker or load generator

A generator of dynamic loads comprising a mass/spring system composed of a main mass comprising at least one main mass element of mass m2 and of at least one main spring element of stiffness K2, which device comprises an auxiliary mass/spring system, which is coupled to the main mass/spring system and which is composed of an auxiliary mass of mass m3 and of at least one auxiliary spring element of stiffness K3, the assembly exhibiting a first and a second resonant frequency f0 and f21 respectively, and an anti-resonant frequency f1, with and f0<f1<f2, and at least one additional mass comprising at least one additional mass element and a coupling device able to couple the additional mass to the main mass and to decouple it therefrom, so as to modify the frequency of the generator.