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    Wyświetlanie 1-3 z 3
    Tytuł:
    A Multi-Layer Micro-Perforated Panel Structure Based on Curled Space for Broadband Sound Absorption at Low Frequencies
    Autorzy:
    Chu, Jiaming
    Liang, Xiao
    Yang, Zhen
    Liang, Haofeng
    Chen, Tao
    Su, Liang
    Zhou, Zhuo
    Powiązania:
    https://bibliotekanauki.pl/articles/31339792.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    micro-perforated plate
    curled space
    broadband sound absorption
    complex frequency plane method
    Opis:
    In this paper, we propose a multi-layer micro-perforated panel structure based on a curled space for broadband sound absorption at low frequencies, which increases the number of perforated panel layers in a limited space using a curled space. The absorption coefficients of the structure under plane wave conditions were calculated using the transfer matrix method and the finite element method. It is demonstrated that the multilayer micro-perforated panel structure can ensure high absorption (consistently over 90%) in the frequency range of 400~5000 Hz. The sound absorption mechanism of the multi-layer micro-perforated panel structure is investigated by using the acoustic impedance along with the reflection coefficient of the complex frequency surface. In addition, we also discuss the effects of the micro-perforated panel parameters on the structural sound absorption coefficient. The results show that the proposed multi-layer micro-perforated panel structure provides an excellent solution for sound absorption in a limited space.
    Źródło:
    Archives of Acoustics; 2023, 48, 4; 529-538
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Prediction of the Tonal Airborne Noise for a NACA 0012 Aerofoil at Moderate Reynolds Number Using a Transitional URANS Approach
    Autorzy:
    De Gennaro, M.
    Küehnelt, H.
    Zanon, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/178116.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    tonal airborne noise
    NACA 0012
    Laminar Boundary Layer-Vortex Shedding noise
    Ladder-like tonal structure of the acoustic spectrum
    multi-tonal structure of the acoustic spectrum
    Opis:
    Tonal airborne noise of aerofoils appears in a limited range of moderate Reynolds numbers and angles of attack. In these specific conditions, the aerofoil is characterised by a large region of laminar flow over the aerodynamic surface, typically resulting in two-dimensional laminar instabilities in the boundary layer, generating one or more acoustic tones. The numerical simulation of such phenomenon requires, beside an accurate prediction of the unsteady flow field, a proper modelling of the laminar to turbulent transition of the boundary layer, which generally imposes the use of highly CPU demanding approaches such as large eddy simulation (LES) or direct numerical simulation (DNS). This paper aims at presenting the results of numerical experiments for evaluating the capability of capturing the tonal airborne noise by using an advanced, yet low computationally demanding, unsteady Reynolds-averaged Navier-Stokes (URANS) turbulence model augmented with a transitional model to account for the laminar to turbulent transition. This approach, coupled with the Ffowcs Williams and Hawkings (FW-H) acoustic analogy, is adopted for predicting the far-field acoustic sound pressure of a NACA 0012 aerofoil with Reynolds number ranging from 0.39 · 106 to 1.09 · 106. The results show a main tone located approximately at 1.6–1.8 kHz for a Reynolds number equal to 0.62 · 106, increasing to 2.4 kHz at Reynolds number equal to 0.85 · 106 and 3.4 kHz at 1.09 · 106, while no main tones are observed at 0.39 · 106. The computed spectra confirm that the acoustic emission of the aerofoil is dominated by tonal structures and that the frequency of the main tone depends on the Reynolds number consistently with the ladder-like tonal structure suggested by Paterson et al. Moreover, in specific conditions, the acoustic spectra exhibit a multi-tonal structure visible in narrowband spectra, in line with the findings of Arbey and Bataille. The presented results demonstrate the capability of the numerical model of predicting the physics of the tonal airborne noise generation.
    Źródło:
    Archives of Acoustics; 2017, 42, 4; 653-675
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Airborne and Structure-Borne Noise Control in the MB Truck Cabin Interior by the Noise Reduction in the Transmission Path
    Autorzy:
    Mohammadi, Nader
    Powiązania:
    https://bibliotekanauki.pl/articles/31339935.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    truck noise sources
    airborne noise
    structure-borne noise
    acoustic materials
    viscoelastic layer damping
    modal analysis
    Opis:
    In the current study, investigations are made to control the MB truck cabin interior noise by reducing noise in the transmission path. The main sources of cabin noise include the engine, exhaust system, air inlet system, driveline system, and tyres (especially at higher speeds). Furthermore, vibrations of the body and interior parts of the truck may significantly impact the overall in-cabin sound level. Noise is transmitted into the cabin via air (airborne noise) and cabin structure (structure-borne noise). In the noise treatment phase, noise transmission paths are considered. A viscoelastic layer damping material is used to reduce the vibration amplitude of the cabin back wall. The overall loss factor and vibration amplitude reduction ratio for the structure treated is calculated. Computational results are then compared with the values obtained by the experimental modal analysis results. Choosing the suitable material and thickness can significantly reduce the vibration amplitude. A sound barrier, silicon adhesive, and foam are also utilised for noise control in the transmission path. The effectiveness of the mentioned acoustic materials on cabin noise reduction is evaluated experimentally. The experimental SPL values are reported in the frequency range of 20 Hz–20 kHz based on a 1/3 octave filter. The experimental results show that using acoustics materials reduces the overall in-cabin sound level for a wide range of frequencies.
    Źródło:
    Archives of Acoustics; 2023, 48, 1; 93-101
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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