Transmission loss is measured with different samples of light panels and other light-weighted structures used e.g. in aircrafts and transportation means. Measurements are carried out in a 4-microphone impedance tube. The samples are fitted between two 75 micrometer foils. The inner part is slightly evacuated to some hundred hPa. Samples show a dramatic increase in transmission loss (TL) to about 50 dB at frequencies below about 300 Hz. The same effect is observed if the foils are fitted between two solid (panel) structures and the inner part is pressurized. The increase in TL is assumedly attained by an increase in stiffness of the foil, which is pressed against the rigid structure, due to the applied pressure difference. The general effect of increased stiffness is described by Ingard 1953 for membranes as a 'mass-like' behavior. The analytic formula of Ingard reflects approximately the observed measurements. Measurements and tests with different panel constructions are carried out within a laboratory project of the engineering physics students.


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    Title :

    Improved transmission loss of light-weighted panels by pressure-difference increased stiffness


    Contributors:


    Publication date :

    2009


    Size :

    7 Seiten, 6 Bilder, 4 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English





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