Download or read book Two Dimensional Fourier Transform Applied to Helicopter Flyover Noise written by Odilyn L. Santa Maria and published by . This book was released on 1999 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Two Dimensional Fourier Transform Applied to Helicopter Flyover Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-12 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: A method to separate main rotor and tail rotor noise from a helicopter in flight is explored. Being the sum of two periodic signals of disproportionate, or incommensurate frequencies, helicopter noise is neither periodic nor stationary, but possibly harmonizable. The single Fourier transform divides signal energy into frequency bins of equal size. Incommensurate frequencies are therefore not adequately represented by any one chosen data block size. A two-dimensional Fourier analysis method is used to show helicopter noise as harmonizable. The two-dimensional spectral analysis method is first applied to simulated signals. This initial analysis gives an idea of the characteristics of the two-dimensional autocorrelations and spectra. Data from a helicopter flight test is analyzed in two dimensions. The test aircraft are a Boeing MD902 Explorer (no tail rotor) and a Sikorsky S-76 (4-bladed tail rotor). The results show that the main rotor and tail rotor signals can indeed be separated in the two-dimensional Fourier transform spectrum. The separation occurs along the diagonals associated with the frequencies of interest. These diagonals are individual spectra containing only information related to one particular frequency.Santa Maria, Odilyn L.Langley Research CenterFOURIER TRANSFORMATION; AIRCRAFT NOISE; FOURIER ANALYSIS; AERODYNAMIC NOISE; AEROACOUSTICS; HELICOPTERS; SPECTRUM ANALYSIS; FLIGHT TESTS; TAIL ROTORS

Download or read book NASA Langley Scientific and Technical Information Output 1999 written by and published by . This book was released on 2000 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1991 with total page 1698 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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Download or read book Verti flite written by and published by . This book was released on 1999 with total page 594 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computation of Two Dimensional Fourier Transforms for Noisy Band Limited Signals written by Weidong Chen and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The computation of the two-dimensional Fourier transform by the sampling points creates an ill-posed problem. In this chapter, we will cover this problem for the band-limited signals in the noisy case. We will present a regularized algorithm based on the two-dimensional Shannon Sampling Theorem, the two-dimensional Fourier series, and the regularization method. First, we prove the convergence property of the regularized solution according to the maximum norm. Then an error estimation is given according to the L2-norm. The convergence property of the regularized Fourier series is given in theory, and some examples are given to compare the numerical results of the regularized Fourier series with the numerical results of the Fourier series.

Download or read book Inversion Based Fourier Transform as a New Tool for Noise Rejection written by Mihály Dobróka and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, a new inversion method is presented for performing two-dimensional (2D) Fourier transform. The discretization of the continuous Fourier spectra is given by a series expansion with the scaled Hermite functions as square-integrable set of basis functions. The expansion coefficients are determined by solving an overdetermined inverse problem. In order to define a quick algorithm in calculating the Jacobian matrix of the problem, the special feature that the Hermite functions are eigenfunctions of the Fourier transformation is used. In the field of inverse problem theory, there are numerous procedures for noise rejection, so if the Fourier transformation is formulated as an inverse problem, these tools can be used to reduce the noise sensitivity. It was demonstrated in many case studies that the use of Cauchy-Steiner weights could increase the noise rejection capability of geophysical inversion methods. Following this idea, the two-dimensional Fourier transform is formulated as an iteratively reweighted least squares (IRLS) problem using Cauchy-Steiner weights. The new procedure is numerically tested using synthetic data.

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Download or read book Aeroacoustics of Flight Vehicles written by Harvey H. Hubbard and published by . This book was released on 1991 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement Resolution of Noise Directivity Patterns from Acoustic Flight Tests written by David Alan Conner and published by . This book was released on 1989 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aeronautical Engineering A Cumulative Index to a Continuing Bibliography supplement 300 written by and published by . This book was released on 1994 with total page 686 pages. Available in PDF, EPUB and Kindle. Book excerpt: