Feasibility study on the efficiency of parametric damping for attenuation of environmental noise

A new semi-active damping approach for the reduction of transmitted acoustic noise is investigated. It involves the controlled variation of the system's spring constant in response to the system's motion in such a way as to maximize the energy lost in the damping elements. A Discrete Mechanics simulation of a prototypical spring-mass-damper system is used to compare the performance of this approach with the semi-active viscous damping approach being applied to this problem today. It is found that: (1) Parametric damping does not require precise phase matching between the noise signal and the response of the system. (2) "Runaway" catastrophes associated with the nonlinear response of the spring constant are avoided by saturating the response of the spring. (3) An algorithm that controls the response of the element by recognizing when it is storing undesired energy suffices to attenuate harmonic and transient noise below 1:1 transmissibility for all frequencies at and below resonance.