In this paper, vibration transmissibility of a single-degree-of-freedom (SDOF) for a mass-springdamper system is presented. This is done with a linear damper having a configuration perpendicular to a linear vertical spring. The method is analyzed using a nonlinear frequency analysis approach. The concept of the output frequency response function (OFRF) is used to derive an explicit polynomial relationship between the system output response (relative displacement of the mass) and the nonlinear damping coefficient which is the parameter of interest. With the derived OFRF polynomial, various damping parameters were designed for desired output responses. Real-time experimental results are presented for the vibration isolation system validation with dampers orientated perpendicularly (at 90 degrees) to the linear spring. The experimental case studies are provided to demonstrate the new OFRFbased nonlinear system design and its significance in isolated vibration system applications. A force transmissibility graph showing the system output using both numerical and the OFRF methods are presented.N/