NOVI - Advanced functional solutions for Noise and Vibration reduction of machinery: Deliverable D1.1 Physical mechanisms of absorption and sound insulation

Seppo Uosukainen

    Research output: Book/ReportReport

    Abstract

    Absorption of acoustic wave is due to viscous and thermal losses and relaxation processes in fluid: - Absorption is emphasized near boundaries, especially in small holes, slits and narrow tubes, - Viscous losses dominate with small free space dimensions: -Perforated / microperforated plates, - Absorbing materials: "Holes" and "slits" described by fluid bulk properties (flow resistivity, porosity, tortuosity, viscous andthermal characteristic lengths). Sound transmission of a wall is due to two parallel transmission paths: - Non-resonant and resonant transmission, - Below coincidence frequency non-resonant transmission dominates except in the resonance region. With double walls above double-wall resonance, sound insulations in dBs are summed with reasonable amount of absorption in cavity if mechanical coupling is insignificant.
    Original languageEnglish
    PublisherVTT Technical Research Centre of Finland
    Number of pages45
    Publication statusPublished - 2014
    MoE publication typeD4 Published development or research report or study

    Keywords

    • sound absorption
    • sound insulation
    • physical mechanisms

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