The present work is related to acoustic in situ free-field measurements of sound absorption in porous materials, such as cellular plastic foams, glass-wool or recycled felt materials. The emphasis is given towards fine metrology of absorption in view of potential industrial applications. A powerful ultrasonic array working at 40 kHz is used. It enables to measure absorption acoustical data down to 100 Hz due to the exploitation of the non-linear ultrasonic demodulation phenomenon in air. Fine measurements of acoustic absorption are compared to numerical predictions based on the 'equivalent-fluid' model (when the squeleton frame is motionless), and to some measurements performed on a Bruel and Kjaer impedance tube. Dispersion curves are also measured and compared to the numerical predictions for some automotive felt materials which are compressed at various ratios. Data obtained with a dedicated portable instrument are also discussed for the same type of materials and configurations.


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    Title :

    Low frequency in situ metrology of absorption and dispersion of sound absorbing porous materials based on high power ultrasonic non-linearly demodulated waves


    Additional title:

    Niederfrequenz-In-situ-Messung von Absorption und Dispersion schallabsorbierender poröser Werkstoffe auf Basis von durch Hochleistungsultraschall nichtlinear demodulierten Wellen


    Contributors:

    Published in:

    Applied Acoustics ; 69 , 7 ; 634-648


    Publication date :

    2008


    Size :

    15 Seiten, 42 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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