| 1. |
- Almquist, Martin, et al.
(författare)
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Atmospheric Sound Propagation Over Large-Scale Irregular Terrain
- 2014
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Ingår i: Journal of Scientific Computing. - : Springer Science and Business Media LLC. - 0885-7474 .- 1573-7691. ; 61:2, s. 369-397
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
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| 3. |
- Andersson, B. L., et al.
(författare)
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Assessment of sound propagation modelling from a wind turbine site at sea
- 2009
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Ingår i: 16th International Congress on Sound and Vibration 2009, ICSV 2009. - 9781615677368 ; , s. 896-903
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 4. |
- Bolin, Karl, 1977-, et al.
(författare)
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An investigation of the influence of the refractive shadow zone on wind turbine noise
- 2020
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America. - 0001-4966 .- 1520-8524. ; 148:2, s. EL166-EL171
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Tidskriftsartikel (refereegranskat)abstract
- This article aims to investigate if the proportion of the rotor area of a wind turbine that is in the refractive shadow zone according to a ray tracing algorithm coupled to meteorological forecast data is correlated to sound levels and amplitude modulation. The acoustic station is situated 950 m from a wind farm in Northern Sweden and the measurement period is seven months. On average, 1.9 dBA lower sound levels are measured when the part of the rotor disk of the closest turbine is in the refractive shadow zone. A higher probability of amplitude modulations are observed when around half of the turbine rotor is within the refractive shadow zone compared to conditions with no shadow zone present.
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| 5. |
- Bolin, Karl, et al.
(författare)
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Long range sound propagation over a sea surface
- 2009
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 126:5, s. 2191-2197
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Tidskriftsartikel (refereegranskat)abstract
- 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]
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| 6. |
- Bolin, Karl, et al.
(författare)
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Long term estimations of low frequency noise levels over water from an off-shore wind farm
- 2014
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 135:3, s. 1106-1114
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Ilkka, Karasalo, et al.
(författare)
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Assessment of a simplified environmental model for aircraft noise prediction
- 2019
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Ingår i: INTER-NOISE 2019 MADRID - 48th International Congress and Exhibition on Noise Control Engineering. - : SOCIEDAD ESPANOLA DE ACUSTICA - Spanish Acoustical Society, SEA.
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Konferensbidrag (refereegranskat)abstract
- The environmental effects on the noise level on the ground from aircraft near the Arlanda airport are studied by numerical predictions of the acoustic transfer function from the aircraft position to the ground. Sound propagation is modelled by acoustic ray tracing using time-variable 3D atmospheric fields provided by the AROME prognosis model, combined with 2D data on ground topology and ground cover. The acoustic transfer function from selected points on the flight path to the ground is computed as function of range to the ground track at two-hour intervals during a one-year period. The results, aggregated into percentiles of the transfer function, are compared to similarly aggregated results from a simplified model of the atmosphere, the ground and the sound propagation. The simplifications are introduced to reduce the computational demands, are: (i) the ground is flat, (ii) the atmospheric parameters are functions of height only and (iii) rays are not continued beyond their first ground hit.
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| 8. |
- Jalkanen, Jukka-Pekka, et al.
(författare)
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Modeling of ships as a source of underwater noise
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Shipping as a source of underwater noise is increasing. Underwater noise emission levels are seldom considered as a ship design parameter unless low vessel noise is specifically required, like in the case of warships and research vessels. Noise emissions are not regulated yet, but the awareness of possible impacts of noise on marine life is increasing. This paper describes the implementation of a noise source model for the Ship Traffic Emission Abatement Model (STEAM; Jalkanen et al. 2009; 2012; Johansson et al, 2017). The combination of vessel technical description and activity can be used to generate noise source maps which are based on actual ship traffic data. The generated noise source maps can ve used to describe the energy emitted as noise to the water, which facilitates regular annual updates of the noise emissions from ship traffic in the Baltic Sea area.
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