Prediction of the Blocked Force at Impact of Japanese Rubber Ball Source

Characterizing and rating the impact sound isolation of floors and of building structures are important issues in building acoustics. In all standardized test procedures a floor specimen is excited structurally with a standardized impact source and the sound pressure level due to the impact is measured in an adjacent room. Existing standards define several impact sources that should simulate the excitation due to persons walking or jumping on the floor and hence exert only normal forces to the structure. However, the excitation spectrum of the most commonly used lightweight tapping machine according to ISO 140-7 differs significantly from the heavy impact sources according to JIS A 1418-2 (the “rubber ball” and the “bang machine” that are dropped from a defined height to the floor). In order to accurately predict the impact sound isolation of floor assemblies, the excitation mechanism due to impacts from these heavy sources has to be understood and implemented in prediction models. This paper presents a simple analytical model for the “rubber ball” heavy impact source and the suitability of the model is gauged by comparing the predicted blocked force with experiment.