This paper summarizes the main properties of six time-frequency representations, and describes their application to the visualization of typical helicopter rotor noise traces. Time-frequency representations may be a useful tool for the visual analysis of helicopter rotor noise, because they provide Information not available from time- or frequency-domain representations alone, such as the time variations of the spectrum of the signal or its power spectrum, which translate in distinctive patterns on a time-frequency plot. No single representation is best for all cases. The Short-Time Fourier Transform and the spectrogram seem to have the most general usefulness. The Wigner-Ville distribution is useful when the noise events are well separated in time. The Choi-Williams distribution does not offer a significant practical improvement over the Wigner-Ville distribution. The Continuous Wavelet Transform and the scalogram do not appear to offer major advantages over Short-Time Fourier Transform and spectrogram, possibly because the Gaussian mother wavelet used in this study is not specifically tailored for helicopter rotor noise. Time-Frequency Representations require some tuning to achieve the most informative results; the specific parameters depend on the representation. This tuning is typically simple, and is not a major practical obstacle.


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    Title :

    Time-frequency visualization of helicopter noise


    Additional title:

    Zeit-Frequenz-Visualisierung von Hubschrauberlärmemissionen


    Contributors:
    Celi, R. (author)

    Published in:

    Publication date :

    2001


    Size :

    11 Seiten, 14 Bilder, 11 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




    Time Frequency Visualization of Helicopter Noise

    Celi, R. | Online Contents | 2001


    Study of helicopter noise signals using time-frequency analysis methods

    Siegert, R. / Nouals, C. / Damongeot, A. | AIAA | 1993


    Helicopter noise

    Davidson, I.M. / Hargest, T.J. | Engineering Index Backfile | 1965


    Helicopter noise

    Cox, C. M. | NTRS | 1983


    Helicopter Linear Noise

    Hans R. Aggarwal | AIAA | 1985