It's similar for cars, for example. You have a lot of engine configurations, such as V6, having inherent 1st order imbalance, but in most cases, for example, most 60-degree V6s, you just live with it because hydraulic engine mount and other normal dampening mechanism does the job well. However, for I4 with inherent 2nd order imbalance, usually you would need counter-rotating twin balancer shafts to help cancel the vibration, although the absolute amount of NVH is actually weaker. That's all because of the higher frequency nature of this 2nd order thing.Hydraulic dampeners can also cancel out lower frequency noises, and they did exactly just that for the 054A and 056 series. You can also reduce vibrations further with viscous dampers, counterbalancing or contrarotating shafts, flexible engine mounts, stiffening the engine block, and even to controlling the fuel injection.