Reflective silencers (using the Helmholtz resonator principle) may take the form of a series resonator (low frequency filter, which transmits sounds at a frequency lower than its own frequency), shunt (high frequency filter, which effectively suppresses sounds close to its own frequency) or create multi-stage and mixed systems. For each specific engine (or rather its acoustic spectrum) and the expected effect, an appropriate system of damping resonators is selected, by manipulating the capacities of individual chambers, hole diameters, distance between the ends of the cables, their diameters, etc..