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  • 1. Almquist, Martin
    et al.
    Karasalo, Ilkka
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Mattsson, Ken
    Atmospheric Sound Propagation Over Large-Scale Irregular Terrain2014In: Journal of Scientific Computing, ISSN 0885-7474, E-ISSN 1573-7691, Vol. 61, no 2, p. 369-397Article in journal (Refereed)
    Abstract [en]

    A benchmark problem on atmospheric sound propagation over irregular terrain has been solved using a stable fourth-order accurate finite difference approximation of a high-fidelity acoustic model. A comparison with the parabolic equation method and ray tracing methods is made. The results show that ray tracing methods can potentially be unreliable in the presence of irregular terrain.

  • 2. Andersson, B. L.
    et al.
    Bolin, Karl
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Cederholm, A.
    Karasalo, Ilkka
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. FOI - Swedish Defence Research Agency, Sweden .
    Assessment of sound propagation modelling from a wind turbine site at sea2009In: 16th International Congress on Sound and Vibration 2009, ICSV 2009, 2009, p. 896-903Conference paper (Refereed)
    Abstract [en]

    We present results from numerical modelling of sound propagation from Utgrunden lighthouse in Kalmarsund to a receiver at Hammarby on the island Ö land east of Sweden in the Baltic. The propagation distances from source to shore and from shore to receiver are ca 9 km and 0.7 km, respectively. Our purpose is to assess prediction of atmospheric sound propagation by methods that use detailed knowledge of the local geometry and meteorology, by comparing model predictions of the transmission loss with experimental data. The experimental data, collected several times daily during a one-week campaign in June 2005, consist of (i) data on the transmission loss of narrow band signals from controlled sources with frequencies 80 Hz, 200 Hz and 400 Hz, (ii) atmospheric parameters as function of height from radio-soundings and balloon-tracking at the receiver location and (iii) atmospheric parameters from sensors mounted on a meteorological mast at the source location. Model-predicted soundfields were computed once per hour during the one-week period, with a windfield composed of a laminar field determined from data at the receiver, superimposed by a turbulent field determined by data from the meteorological mast. Comparisons of the experimentally observed transmission loss with predictions by the Green's Function Parabolic Equation (GFPE) method by Gilbert and Di are presented. A reasonably good fit of the model predicted transmission loss as function of time to experimental data at all frequencies is observed.

  • 3.
    Bolin, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Almgren, Martin
    Ohlsson, Esbjörn
    Karasalo, Ilkka
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Long term estimations of low frequency noise levels over water from an off-shore wind farm2014In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 135, no 3, p. 1106-1114Article in journal (Refereed)
    Abstract [en]

    This article focuses on computations of low frequency sound propagation from an off-shore wind farm. Two different methods for sound propagation calculations are combined with meteorological data for every 3 hours in the year 2010 to examine the varying noise levels at a reception point at 13 km distance. It is shown that sound propagation conditions play a vital role in the noise impact from the off-shore wind farm and ordinary assessment methods can become inaccurate at longer propagation distances over water. Therefore, this paper suggests that methodologies to calculate noise immission with realistic sound speed profiles need to be combined with meteorological data over extended time periods to evaluate the impact of low frequency noise from modern off-shore wind farms.

  • 4.
    Bolin, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Boue, Mathieu
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Karasalo, Ilkka
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Long range sound propagation over a sea surface2009In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 126, no 5, p. 2191-2197Article in journal (Refereed)
    Abstract [en]

    This paper describes methodology and results from a model-based analysis of data on sound transmission from controlled sound sources at sea to a 10-km distant shore. The data consist of registrations of sound transmission loss together with concurrently collected atmospheric data at the source and receiver locations. The purpose of the analysis is to assess the accuracy of methods for transmission loss prediction in which detailed data on the local geography and atmospheric conditions are used for computation of the sound field. The results indicate that such sound propagation predictions are accurate and reproduce observed variations in the sound level as function of time in a realistic way. The results further illustrate that the atmospheric model must include a description of turbulence effects to ensure predicted noise levels to remain realistically high during periods of sound shadow. (C) 2009 Acoustical Society of America. [DOI: 10.1121/1.3238236]

  • 5.
    Svensson, Elin
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Karasalo, Ilkka
    Swedish Defence Research Agency, Division of Systems Technology, Stockholm.
    Hermand, Jean-Pierre
    Université Libre de Bruxelles, Dept of Optics and Acoustics.
    Hybrid raytrace modelling of an underwater acoustics communication channel2004In: Proceedings of the Seventh European Conference on Underwater Acoustics, 2004, p. 1211--1216Conference paper (Refereed)
    Abstract [en]

    A hybrid method is described for modelling sound propagation in range-dependent shallow water environments. The method combines ray tracing in a range-dependent water column with local full-field modelling of interactions with a seabed composed of multiple range-dependent layers of fluid or solid materials. The method is assessed by simulations of the Yellow Shark 94 experiments in the Mediterranean, using environmental parameters available from previous acoustic full-field inversions of the experimental acoustic data, and from an oceanographic survey with a towed-oscillating CTD profiler. Results from applying the method to simulation of transmission and decoding of communication signals in the shallow-water waveguide are presented.

  • 6.
    Svensson, Elin
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Karasalo, Ilkka
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Hermand, Jean-Pierre
    Université Libre de Bruxelles, Dept of Optics.
    Time variability of an underwater acoustic channel2003In: Proceedings of the Tenth International Congress on Sound and Vibration: Code 62825 / [ed] Nilson A., Boden H., 2003, p. 2633--2641Conference paper (Refereed)
    Abstract [en]

    Underwater acoustic communication systems deal with the problem of fading multipath propagation as well as Doppler shifts. Knowledge of the channel impulse response considerably simplifies the extraction of information from a transmitted signal. Supposed that the impulse response is known at one time instant, the bit-error rate is here studied using that impulse response for the equalisation at later instants, to get a picture of the time variability of the channel. The study is performed by computer simulations with different modulation schemes using channel impulse responses determined from measurements in the Mediterranean during Yellow Shark 94.

  • 7. Zamanizadeh, E.
    et al.
    Gomes, J.
    Bioucas-Dias, J. M.
    Karasalo, Ilkka
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Performance analysis of model-based localization of high-frequency acoustic sources in 3D2013In: OCEANS 2013 MTS/IEEE Bergen: The Challenges of the Northern Dimension, 2013Conference paper (Refereed)
    Abstract [en]

    A robust model-based source localization (MBSL) scheme for 3D positioning of high-frequency underwater acoustic (UWA) transmitters, as well as performance assessment of 3D speed vector estimation of the acoustic source, deploying two linear receiver arrays, is developed and evaluated. In addition, this paper presents the sensitivity evaluation of MBSL to uncertainties involved in environmental parameters, including the effects of sound speed profile and bathymetry mismatches. The results presented here pertain to the general framework of inferring side information concerning an UWA link from the environmental signature imprinted on waveforms by the propagation medium. The presented algorithms directly operate on estimated linear time-varying UWA channel responses, represented as 3-dimensional delay-Doppler-depth functions (DDDF). Estimation of DDDF coefficients is achieved jointly for all receivers deployed at different depths using Basis-Pursuit (BP) tools, which can efficiently handle sparse unconstrained ℓ2 - ℓ1 minimization, and directly operate on the complex signals of baseband models. To extract delay/Doppler information related to each path from the DDDF representation, an efficient energy-based scheme is developed to detect and label wavefronts using clustering techniques inspired by image processing.

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