Helmholtz resonators ban noise3 Apr 2014
Street noise, construction noise, airplane noise – noise levels in cities are on the rise. Adaptronics offers cutting-edge approaches to keeping noise out of homes and offices – using adaptive Helmholtz resonators. Scientists from the Fraunhofer Institute for Structural Durability and System Reliability LBF developed this innovative technology and are presenting it at HANNOVER MESSE 2014. The Fraunhofer Adaptronics Alliance is showcasing smart adaptive and active structural solutions together with its research and business partners for the eighth time in Hannover; this year's exhibits include a smart model bridge.
The noise reduction demonstration involves an "acoustic aquarium" – a box in which a loudspeaker generates an acoustic field. Two Helmholtz resonators are built in to reduce sound transmission from the speaker through a double-glazed window. Helmholtz resonators reduce passive acoustic fields in rooms and through double-glazed windows. The advantage of this passive system compared with active measures to reduce noise: it consumes significantly less energy. One possible application: airplane builders could keep noise out of passenger cabins using this technology.
A second research project addresses the deteriorating condition of road bridges in Germany. Scientists from Fraunhofer LBF and TU Darmstadt have developed a system that can determine the properties of oscillations caused by traffic-induced vibrations in bridges. Observing how these properties evolve over time can help identify potential damage at an early stage. The demo model is impressive: a 51.4-kilogram lattice framework simulating a truss bridge is set in motion by the crossing of a 4.2-kilogram model train. Twenty acceleration sensors detect the resulting vibrations.
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