Author(s): Bietz Heinrich, Wittstock Volker
The dynamic stiffness of elastic insulation materials is an important material parameter in building acoustics and must be known, for example, in order to predict the resonance frequency of floating floors. The measurement procedure used to determine the dynamic stiffness of elastic layers for floating floors is described in DIN EN 29052-1. Here, a defined mass is applied to a sample of the elastic layer and from the resonance frequency of this spring-mass system, the resonance frequency is determined. With regard to the metrological realization (excitation of the measurement set-up, the arrangement of the sensors and the analysis of the of the resonance curve), however, the standard leaves many unanswered questions. Also, correction by means of the airflow resistance, as described in the standard, definitely raises questions. Within the scope of a research project to study the physical properties of sustainable insulation materials, an investigation of these questions was conducted at PTB. In the context of the research project, also insulation materials are to be investigated which are used for thermal insulation composite systems (or are planned to be used for these), bringing about a clearly smaller static preload than floating floors. As, in our experience, the dynamic stiffness of insulating materials depends on the static preload, alternatives for the standardized measuring set-up were considered which allow a realistic determination of the dynamic stiffness at a small static load.
Name: Mr Heinrich Bietz