A system consisting of a primary structure coupled with a passive tuned vibration absorber is experimentally studied. The primary structure consists of four flexible columns with a mass, while the absorber consists of a beam with a tip-mass. The system. which is a coupled non-linear oscillator, is subjected to sinusoidal and random excitation. The effects of the forcing frequency, forcing amplitude. mass ratios and frequency ratios on the displacement response of the system in the neighbourhood of the autoparametric region are studied. Control parameters related to effectiveness of the absorber are determined. The objective of this study is to experimentally define an absorption region for the passive vibration absorber and to determine the parameters that influence the effectiveness of the vibration absorber. (C) 2002 Academic Press.