| 11. |
- Brunskog, Jonas, et al.
(författare)
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Measurement of the Acoustic properties of resilient, statically tensile loaded devices in light weight structures: A measurement method and statistical analysis
- 2002
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Ingår i: Building Acoustics. ; 9:2, s. 99-137
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Tidskriftsartikel (refereegranskat)abstract
- Resilient devices are commonly used in lightweight structures to decrease sound transmission in a broad frequency band. Applications of such devices may be found in e.g. resilient mounted ceilings in aeroplanes, ships and buildings. A measurement method to characterise the frequency dependency of the transfer stiffness and the input stiffness of the resilient device is presented. The mechanical characteristics of the measurement method are investigated. In addition, some resilient devices used in buildings are analysed with respect to acoustic properties. Parameters such as static load and mountings for the devices are considered and handled by means of statistical analysis.
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| 12. |
- Brunskog, Jonas
(författare)
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Near-periodicity in acoustically excited stiffened plates and its influence on vibration, radiation and sound insulation
- 2004
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Ingår i: Acta Acustica united with Acustica. - 1436-7947. ; 90:2, s. 301-312
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Tidskriftsartikel (refereegranskat)abstract
- Due to variabilities in the material, the geometrical configuration, or the manufacturing properties, a structure that is designed to be spatially periodic cannot be exactly periodic. The presence of small irregularities in a nearly periodic structure may influence the propagation of the vibration field, the field being localised. A number of papers have addressed such localisation phenomena. This paper will instead focus on the mean vibration field and its influence on sound radiation and sound insulation in a plate stiffened by supports or beams. The approach is to seek a formal solution with the aid of spatial transform technique (similar to the perfect periodic case) and then apply the expected value operator to the solution. Two assumptions must then be introduced: 1) The reaction forces are statistically independent of a phase-term that is due to the irregularity, and 11) the mean field is periodic. The approach is presented in general terms, the specific configuration (a stiffened plate) being presented as an example. Numerical results are presented and discussed, and it can be seen that the small irregularities cause an increase in stiffness and damping (when material damping is present).
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| 13. |
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| 14. |
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| 15. |
- Brunskog, Jonas, et al.
(författare)
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Prediction model for the impact sound level of lightweight floors
- 2003
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Ingår i: Acta Acustica united with Acustica. - 1436-7947. ; 89:2, s. 309-322
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Tidskriftsartikel (refereegranskat)abstract
- Lightweight floors are often troubled by poor impact-sound insulation. In order to develop and explain structures with acceptable insulation, a deterministic prediction model was developed. The paper considers transmission through the system and the response of the model. Excitation (as caused by the ISO-tapping machine) is considered in a separate paper [1]. The system description employs a spatial transform technique, making use of the periodicity of the floor structure with the aid of Poisson's sum rule. The radiated power is calculated using numerical integration in the wave-number domain, the radiated power enabling the impact sound level to be calculated. Comparisons are made between measurements found in the literature and the proposed prediction model, the effects of different excitation models being discussed. A relatively close agreement is achieved, especially if an elaborate excitation model is employed.
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| 16. |
- Brunskog, Jonas, et al.
(författare)
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Rigid indenter excitation of plates
- 2003
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Ingår i: Acta Acustica united with Acustica. - 1436-7947. ; 89:3, s. 460-470
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents expressions for the point mobility of infinite plates driven by a completely rigid indenter. The problem is of general interest in connection with the excitation and transmission of structure-borne sound. The indenter is assumed to be circular, weightless, and stiff compared with the plate. A rigid indenter is assumed to provide a better approximation of the actual situation than a soft indenter would, e.g when a hammer acts on a wooden plate. A detailed three-dimensional analysis is performed. Traditionally, the problem is solved in approximate terms by assuming a pressure distribution at the interface between the indenter and the plate. In the present study, a pressure distribution is also assumed, an optimal choice of the pressure amplitude being found by means of a variational formulation. Numerical results are presented and discussed, the discrepancy between the results obtained and the perfectly rigid indenter being examined.
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| 17. |
- Brunskog, Jonas, et al.
(författare)
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Sound transmission between infinite rooms; a modal approach and fe-formulation
- 2003
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Ingår i: Proceedings of the 10th International Congress on Sound and Vibration. ; , s. 4541-4548
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Konferensbidrag (refereegranskat)abstract
- A full description of the entire system room-wall-room in a theoretical model for sound insulation is still today too computation intensive, implying that the higher frequencies cannot be studied. Some simplifications must thus be introduced. The simplification proposed in the present paper is to replace the rooms with wave-guides, i.e. infinity long rooms. The model then reduces to the (more or less) two-dimensional wall. The question of how to apply the excitation then arises. The choice herein is to use a combination of diffuse field and Monte Carlo simulations. The incident and radiated power, expressed in the wave-guide modes, is used to calculate the transmission loss. A minor literature survey is also included.
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| 18. |
- Brunskog, Jonas, et al.
(författare)
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Sound transmission of structures. A finite element approach with simplified room description
- 2004
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Ingår i: Acta Acustica united with Acustica. - 1861-9959. ; 90:5, s. 847-857
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical prediction model for the sound insulation of a wall is an important tool when developing new wall structures. A full description of the entire room-wall-room system in a theoretical model for sound insulation is still today too computation-intensive, implying that the sound insulation at higher frequencies cannot be studied. Some simplifications must thus be introduced. The simplification proposed in this present paper is to describe the rooms with waveguides, i.e., infinity-long rooms. The model then reduces to the (more or less) two-dimensional wall. The question of how to apply the excitation then arises. The choice proposed here is to use a combination of diffuse field and Monte Carlo simulations. The incident and radiated power, expressed in waveguide modes, are used to calculate the transmission loss. A minor literature survey is also included, as well as numerical results and comparison with experimental results. The method presented is developed to study the sound insulation of lightweight double-leaf walls, and the numerical results of such walls are presented.
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| 19. |
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| 20. |
- Brunskog, Jonas
(författare)
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The influence of finite cavities on the sound insulation of double-plate structures
- 2005
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 117:6, s. 3727-3739
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Tidskriftsartikel (refereegranskat)abstract
- Lightweight walls are often designed as frameworks of studs with plates on each side-a double-plate structure. The studs constitute boundaries for the cavities, thereby both affecting the sound transmission directly by short-circuiting the plates, and indirectly by disturbing the sound field between the plates. The paper presents a deterministic prediction model for airborne sound insulation including both effects of the studs. A spatial transform technique is used, taking advantage of the periodicity. The acoustic field inside the cavities is expanded by means of cosine-series. The transmission coefficient (angle-dependent and diffuse) and transmission loss are studied. Numerical examples are presented and comparisons with measurement are performed. The result indicates that a reasonably good agreement between theory and measurement can be achieved.
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