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KU Leuven Designs Alternative to Impedance Tube

Katholieke Universiteit Leuven's (KU Leuven) Department of Mechanical Engineering is working on an ongoing project designed to offer an alternative to impedance tube testing. The University's "Sound Box" research involves a concrete walled cavity with 12 1/2-in. prepolarized free-field condenser microphones and 1/2-in. prepolarized random-incidence condenser microphones. The microphones are placed both in and outside the cavity and uniaxial lightweight accelerometers are mounted to the test specimen to measure the vibration levels. Triax accelerometers are mounted on the rigid frame to assess mounting structure rigidity. One hundred lbf shakers, in combination with impedance heads, are used to investigate structure-borne phenomena, whereas loudspeaker excitation is used for air-borne phenomena assessment. 

The test shows panel and material parameters such as insertion loss, absorption, etc. Current testing standards for materials like impedance tube testing, transmission loss testing, etc., don't reflect the conditions typically encountered in real-life machinery or vehicles. "We wanted to come up with a device better suited for real world conditions," says Wim Desmet, full professor and head of the KU Leuven Noise and Vibration research group.
Numerical simulation approaches, in combination with experimental setups such as this test rig, are being used at KU Leuven for the analysis and design of innovative lightweight structures with optimal acoustic performance and design of liner materials for the acoustic treatment of flow confining ducts.
Read the full paper "Study of the Vibro-Acoustic Behaviour of Composite Sandwich Structures by Means of a Novel Test Setup" below:

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