Acoustic modeling of fan noise generation and scattering in a modular duct system

M.J.J. Nijhof, W.M. Beltman, Ysbrand H. Wijnant, Andries de Boer

    Research output: Contribution to conferencePaper

    1 Citation (Scopus)
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    Fan noise is an important noise source in computers. The noise spectrum of fans contains tonal noise, found at the so-called Blade Passing Frequency (BPF) and its higher harmonics, that plays an important role in the perceived sound quality. An acoustic resonator integrated in the duct of an in-duct axial fan causes an impedance change in the duct and, depending on the dimensions and location, the resonator acts as an acoustic mirror reflecting the noise back to the fan. By using a resonator on both the inlet and outlet side of the fan the emitted noise can be contained between the resonators thus reducing the noise radiated to the surroundings. In previous publications by the authors, a model was outlined describing viscothermal wave propagation in the duct and in different resonator geometries. A model of the complete resonator setup can be constructed by coupling the solutions for wave propagation in the different elements of the setup. Such a modular model can be used to determine the resonator dimensions and position to optimally reflect noise near the BPF. An important factor in this model is the element that describes noise generation and scattering of incident sound waves by the fan. The description of such an element was not yet available and is presented in this paper. Furthermore, an experimental setup is presented that was built to obtain the different model parameters and to experimentally validate the theory.
    Original languageEnglish
    Number of pages8
    Publication statusPublished - 11 Jul 2005
    Event12th International Congress on Sound and Vibration, ICSV 2005 - Lisbon, Portugal
    Duration: 11 Jul 200514 Jul 2005
    Conference number: 12


    Conference12th International Congress on Sound and Vibration, ICSV 2005
    Abbreviated titleICSV


    • METIS-229331


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