1. Low-speed hum

In an internal combustion engine, excitations come mainly from combustion-related forces and inertial forces acting on the moving linkage. When the engine is running at low revs, the acyclism generated by combustion is predominant over that produced by the inertial forces acting on the moving linkage. These high torsional excitations on the engine side can be more or less attenuated depending on the choice of transmissions. As a result, low-speed hum is reflected in a high level of vibration at the rocket carrier.