| 1. |
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| 2. |
- Brunskog, Jonas
(författare)
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A wave approach to structural transmission loss in periodic structures: Thin beam case
- 2005
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Ingår i: Acta Acustica united with Acustica. - 1861-9959. ; 91:1, s. 91-102
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Tidskriftsartikel (refereegranskat)abstract
- When new building systems are developed, these are often lightweight constructions with a periodical set of stiffeners, developed for use in load-bearing structures and dwellings. One of the main drawbacks of this type of building systems is the sound insulation, where flanking transmission is an important issue. A prediction model for flanking transmission of lightweight building structures is thus under development. This paper is a theoretical study of the structural transmission coefficient of a junction, using a propagating wave approach. Free waves travel in the periodic wave-medium. The periodic resilient elements consist of rotation and displacement springs. The free waves meet a discontinuity (or junction), and the power transmitted through the discontinuity is then studied. The discontinuity consists of a mechanical coupling and point mass load. The model is analytic and deterministic, and makes use of a spatial Fourier transform wave approach for periodic structures. The approach is intended for flanking transmission of lightweight building structures, but it is also applicable for structures such as ships and aircraft. Numerical results are presented and discussed. It is concluded that the periodic nature of the wave media affects the power transmitted through a discontinuity.
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| 3. |
- Brunskog, Jonas, et al.
(författare)
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Absorption and scattering by perforated facings with periodic narrow slits
- 2022
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 151:3, s. 1847-1859
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Tidskriftsartikel (refereegranskat)abstract
- This paper develops a theory for the sound absorption and scattering of perforated slit absorbers.A rigid plane, perforated periodically in one dimension with absorbing slits, scatters incoming sound waves as discrete wave components in different directions. The absorbing slits are assumed to be line-like in the sense that their width is much shorter than the wavelengths.The equation for the sound field is solved in the wavenumber domain. The slits are described with an impedance description, assuming local reaction of the slits (typically a Helmholtz resonator).The solution is found by means of an inverse transform, back to the spatial domain. This results in an explicit formulation of the sound field, including a sum consisting of components that either radiate energy in discrete directions or are surface waves.A similar sum is also included in a term that can be interpreted as radiation impedance. The explicit expressions for the absorption and scattering coefficients are found with the aid of the radiating part of the scattered and reflected field.Numerical results of the absorption and scattering coefficients are presented. The result is verified with finite element method and compared with the result from an alternative general formulation of the problem.
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| 4. |
- Brunskog, Jonas
(författare)
-
Acoustic excitation and transmission of lightweight structures
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to increase our knowledge of the sound transmission and radiation processes of lightweight wall and floor structures, theoretical models are needed. Detailed models may form a valuable tool. In lightweight floor structures, impact sound insulation is perhaps the most important property to consider. This thesis presents an overview of various solution strategies that may be useful in finding a theoretical model for impact sound insulation. Expressions for the point mobility of infinite plates driven by a rigid indenter are derived. These expressions are needed when determining the deformation close to the excitation area, which is important when studying impact noise to properly describe the interaction between the source and the floor. A detailed three-dimensional thick-plate analysis is used. The excitating pressure is found by means of a variational formulation. The point mobility is calculated by means of numerical integration. The excitation force provided by the ISO tapping machine is examined, partly in relation to the three-dimensional deformation analysis. Results found in the literature are reviewed and reconsidered. Low-frequency asymptotes are derived. A more general impact force description is derived, suited for arbitrary frequency-dependent mobilities of the floor structure. The frequency-dependency of the mobility can be due to local effects, investigated by means of thick-plate theory, and/or global effects, investigated by means of a spatial Fourier transform method. A theoretical model for a point-excited simple lightweight floor is presented. The model is used for the prediction of impact noise level. A comparison between numerical computations and measurements found in the literature is performed. A relatively good correspondence between measurements and calculations can be achieved. Lightweight walls (and floors) are often designed as a framework of studs with plates on each side. The studs can be seen as walls in the cavity, thus introducing finiteness. A prediction model for airborne sound insulation including these effects is presented. Due to variabilities, no structure can be perfectly periodic. The effects of near-periodicity are studied by means of transform technique and the expectation operator. The near-periodicity leads to an increase of the damping (if material damping is present). Resilient devices are commonly used in lightweight structures to decrease the sound transmission in a broad frequency band. Applications of such devices may be found, for example, in resiliently mounted ceilings in aeroplanes, ships and buildings. A measurement method to characterise the two-port acoustic properties of resilient devices is presented.
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| 5. |
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| 6. |
- Brunskog, Jonas
(författare)
-
Flanking transmission of a double-plate system with joists and cavities
- 2004
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Ingår i: 8th International Congress on Acoustics.
-
Konferensbidrag (refereegranskat)abstract
- The work with development of new building systems is intensive. These systems are often related to lightweight constructions, and developed to be used in load-bearing structures and dwellings. One of the main drawbacks of this type of building systems is often the sound insulation. Lightweight walls and floors are often designed as frameworks of studs with plates on both sides - a double-plate structure. The flanking transmission is often the limiting aspect for the total sound insulation of such a structure. A prediction model for flanking transmission of lightweight building structures is thus under development. In the present paper the structural transmission loss when a double-plate structure meets a discontinuity is primary studied theoretically, assuming the incoming wave to be traveling. The model is analytic and deterministic and makes use of a spatial Fourier transform wave approach for periodic structures
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Brunskog, Jonas
(författare)
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Image solution for clamped finite beams
- 2005
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X. ; 287:4-5, s. 1057-1064
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Tidskriftsartikel (refereegranskat)abstract
- An image solution for the forced response of a clamped finite beam is developed. The finite beam is replaced by an infinite beam under spatially periodic excitation and periodic support reactions. The response is then found by a Fourier transform approach, making use of the periodicity. An explicit expression is found, using the Poisson sum formula. The aim is to describe the potential of using the image method for clamped structural acoustic and vibration problems.
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| 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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| 21. |
- Brunskog, Jonas, et al.
(författare)
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The interaction between the ISO tapping machine and lightweight floors
- 2003
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Ingår i: Acta Acustica united with Acustica. - 1436-7947. ; 89:2, s. 296-308
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Tidskriftsartikel (refereegranskat)abstract
- The ISO standard tapping machine, used as an excitation source in rating the impact-sound level of a floor structure, interacts with the floor structure during the hammer impact. Expressions for the force spectrum due to the impact are presented. The 6 dB difference at low frequencies of the force spectrum, evident in measurements, and reasons for it, are discussed. The interaction is investigated by use both of simplified lumped models and arbitrary frequency-dependent models. Local effects due to indentation near the point of impact and to global effects due to stiffeners are included in the description of the mobility involved. Numerical results are presented, where it is concluded that both the local and the global effects of the driving-point mobility are important in describing the force spectrum caused by the interaction between the tapping machine and the complex floor structure.
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| 22. |
- Brunskog, Jonas
(författare)
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Wave-modes of a double-plate system with joists and cavity
- 2003
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Ingår i: Proceedings of the 10th International Congress on Sound and Vibration. ; , s. 4555-4562
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Konferensbidrag (refereegranskat)abstract
- Lightweight walls and floors are often designed as frameworks of studs with plates on each side - a double-plate structure. The free wave-modes and periodic wave motion of a double-plate system reinforced by joists are analysed in the present paper (as the insertion loss and impact sound insulation have been studied in previous papers). The free wave-modes can in a future step be used in connection with flanking transmission. The cavity between the plates is assumed locally reacting. A spatial transform technique is used, making use of the periodicity.
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| 23. |
- Davidsson, Peter, et al.
(författare)
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Analysis of sound transmission loss of double-leaf walls in the low-frequency range using the finite element method
- 2004
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Ingår i: Building Acoustics. - : SAGE Publications. - 1351-010X .- 2059-8025. ; 11:4, s. 239-257
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Tidskriftsartikel (refereegranskat)abstract
- The sound transmission loss of double walls in the low-frequency range is studied by means of structure-acoustic finite element analysis. The analysis simulates standard experiments to determine sound transmission loss of walls. The model is a detailed description of the geometry of the system, including both the double wall and the rooms acoustically coupled to the wall. The frequency range studied is in the 1/3-octave bands between 40 Hz and 200 Hz. A parametric study is performed to investigate the influence on the sound transmission loss of various material and geometric properties of the wall and the dimensions of the connecting rooms. The model confirms the importance of primary structural resonance and the size of the connecting rooms in determining the degree of sound transmission loss. The primary structural resonance is mainly determined by the distance between the wall studs and the properties of the sheeting material. Wall length is also important; if the length is such that the wall studs of the last wall cavity are closer together than those of the other wall cavities, the primary structural resonance will be at a higher frequency, thereby decreasing sound transmission loss over a broader frequency range. Similar dimensions of the connecting rooms results in poor transmission loss, mainly at frequencies below 100 Hz (for the wall and room dimensions studied here).
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| 24. |
- Davidsson, Peter, et al.
(författare)
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Sound reduction in double walls at low frequencies - A parametric study
- 2003
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Ingår i: Proceedings of the 10th International Congress on Sound and Vibration. ; , s. 4601-4608
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Konferensbidrag (refereegranskat)abstract
- The sound transmission in double walls at low frequencies is studied using a detailed geometric model, based on FEM. The model simulates the experiments carried out to determine the sound reduction index of the wall. The wall properties effect on the sound transmission loss is investigated and also how the sound reduction is affected by the dimensions of the connecting rooms.
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| 25. |
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Hammer, Per, et al.
(författare)
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Vibration isolation on light weight floor
- 2002
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Ingår i: Building Acoustics. ; 9:4, s. 257-269
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical and experimental study of vibration isolation for a source on a lightweight floor structure is presented. The effectiveness of one-stage and two-stage isolator systems is studied. Approximate formulae are presented for both low and high frequency for the receiver, the floor structure. For the mobility, a comparison between approximate formulae, numerical exact results and experimental results are presented. The low frequency asymptote for the approximate mobility is valid up to l/p 1/4. The high frequency asymptote is valid from l/p 1/2. A straight line can be drawn between these two points for the intermediate range 1/4 < l/p < 1/2. Finally, a case study is presented. A fan is mounted on a wooden joist floor. The effect of both one and two stage isolation is demonstrated. It is clearly seen that the high mobility situation for the receiver is increased by adding a rigid body to the mount. Hence, in the frequency range of interest, the 'receiver' acts more or less as a blocked termination. A two-stage isolator almost completely eliminates the structure borne sound and compared to a one-stage isolator it reduces the sound by 20 dB at the rpm for the fan.
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| 30. |
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| 31. |
- Lyberg-Åhlander, Viveka, et al.
(författare)
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Part summary of the project 'Speakers' Comfort' : Teachers' voice use in teaching environments
- 2015
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Ingår i: Building Acoustics. - 1351-010X. ; 22:3-4, s. 209-224
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Tidskriftsartikel (refereegranskat)abstract
- Classroom acoustics not always take the speaker's comfort into consideration. The purpose of the presented papers was to investigate voice use, vocal behavior and prevalence of voice problems in Swedish teaching staff. Ratings of features in the work-environment on voice use were explored in n = 487 teachers. Based on their answers the respondents were split into two groups: teachers with self-assessed voice problems and voice-healthy teachers. Teachers with voice problems and were matched to a voice-healthy colleague from the same school and were investigated and compared for clinical findings and for vocal behavior. Acoustic properties of their teaching environments were measured. Teachers with voice-problems were more affected by any loading factor in the work-environment and were more aware of the room acoustics. Differences between the groups were found during field-measurements, while there were no differences in the findings from the clinical examinations of the larynx and voice. Voice problems seem to emerge in the interplay with and use of the classroom acoustics.
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| 32. |
- Lyberg-åhlander, Viveka, et al.
(författare)
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Teachers 'voice use in teaching environment. Aspects on speakers' comfort
- 2015
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 78, s. 3090-3095
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Tidskriftsartikel (refereegranskat)abstract
- Teachers have high occupational voice demands. The voice load of teachers is both environmental and individual. Little is known about the teachers' own view of the contribution from the environment and about the teachers' voice use at their work-place. Aim: The purpose was to investigate the voice use and prevalence of voice problems in teachers and to explore their ratings of vocally loading aspects of their working environment. Method: A questionnaire-survey in 467 teachers aiming to explore the prevalence of voice problems in teaching staff identified teachers with voice problems and vocally healthy colleagues separated in two groups, teachers with self-assessed voice problems and vocally healthy teachers. Teachers with voice problems were further, matched to a voice healthy colleague from the same school. The pairs were investigated and compared for clinical findings and for vocal behavior in the teaching environment and aspects of the classroom environment were also measured. Results: Teachers with voice problems were more affected by any loading factor in the work-environment and were more perceptive of the room acoustics. Differences between the groups were found during field-measurements of the voice, while there were no differences in the findings from the clinical examinations of larynx and voice. Conclusion: Teachers suffering from voice problems react stronger to loading factors in the teaching environment. It is in the interplay between the individual and the work environment that voice problems emerge.
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| 33. |
- Mosharrof, Mohammad Sazzad, et al.
(författare)
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An improved prediction model for the impact sound level of lightweight floors : Introducing decoupled floor-ceiling and beam-plate moment
- 2011
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Ingår i: Acta Acoustica united with Acustica. - 1610-1928 .- 1861-9959. ; 97:2, s. 254-265
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Tidskriftsartikel (refereegranskat)abstract
- To better understand the complex acoustic behaviour of lightweight building structures both experimental and theoretical approaches are necessary. Within the theoretical approach developing theoretical models is of great importance. The aim here is to further develop an existing method to predict the impact sound pressure level in a receiving room for a coupled floor structure where floor and ceiling are rigidly connected by beams. A theoretical model for predicting the impact sound level for a decoupled floor structure, which has no rigid mechanical connections between the floor and the ceiling, is developed. An analytical method has been implemented, where a spatial Fourier transform method as well as the Poisson's sum formula is applied to model transformed plate displacements. Radiated sound power was calculated from these displacements and normalized sound pressure levels were calculated in one-third octave frequency bands. The predicted results from the model are compared with the results from the experiments on the decoupled floor-ceiling construction. The results gave agreements in line with comparisons regarding previous model. The effect of introducing beam-plate moment in the model is studied and is found to be dependent on frequency, showing significant improvement in predicting impact sound level at high frequency region.
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| 34. |
- Mosharrof, Mohammad Sazzad, et al.
(författare)
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Prediction model for the impact sound pressure level of decoupled lightweight floors
- 2009
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Ingår i: 38th International Congress and Exposition on Noise Control Engineering 2009. - Red Hook, NY : Curran Associates, Inc.. - 9781615676903 ; , s. 2038-2046
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Konferensbidrag (refereegranskat)abstract
- Prediction of impact sound insulation in timber buildings is difficult since the constructions are complex, non isotropic and show large variances. There are earlier publications on precise models of simplified structures and simplified models of complex structures, where so far, none is considered as an acceptable simplified engineering model tool. The goal of our research is to develop methodology for such a simplified engineering tool. The starting focus is to model impact sound in a simple floor model of two plates that are realistically coupled via beams. The floor structure in Nordic countries is mostly decoupled, meaning there is either no structural connection or an elastic connection between the plates and the beams. In this paper, an improved floor model is proposed where as a first step there is no physical connection between the plates and beams, and where each plate is stiffened by separate beams. Hence the construction becomes more realistic as only coupling between the plates via air trapped inside the cavity is taken into account. Next step will be to introduce resilient coupling between the respective beams. The modelling show promising results with reasonable sound insulation improvements.
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| 35. |
- Mosharrof, Mohammad Sazzad
(författare)
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Study and modelling of lightweight floor structure regarding its acoustic properties
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lightweight floor structure is widely used in building industries and to have better sound insulation builders come up with different ways of construction. Depending on the construction the floor structure could either be coupled (floor and ceiling coupled by beams) or decoupled (no mechanical connection between floor and ceiling). Although there are many models on coupled structure but for decoupled structure the number is not too many. Keeping that in mind the present thesis talks about lightweight floors: the construction, properties, behaviour etc with a focus on developing a model for decoupled floor structure where the core contribution being the decoupling and adding the moment effect at plate beam joints. The advantage of decoupled structure is that it disconnects the sound bridge through the beams. One consequence on the other hand is that cavity resonance dominates the low frequency region. A comparative analysis is also done with the coupled model. While developing the model this talks about different mathematical tools such as Fourier transform, Floquet principle, Poisson's sum formula etc This also gives an overview of different types of modelling technique available such as analytical, Numerical, energy based approach, empirical method etc. A parametric study is also done here to find out the relative influence of different elements on sound pressure level.
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| 36. |
- Papadimitriou, Georgios, et al.
(författare)
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Sex differences in vocal behavior in virtual rooms compared to real rooms
- 2024
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Ingår i: JASA Express Letters. - : American Institute of Physics (AIP). - 2691-1191. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates speech production under various room acoustic conditions in virtual environments, by comparing vocal behavior and the subjective experience of speaking in four real rooms and their audio-visual virtual replicas. Sex differences were explored. Males and females (N = 13) adjusted their voice levels similarly to room acoustic changes in the real rooms, but only males did so in the virtual rooms. Females, however, rated the visual virtual environment as more realistic compared to males. This suggests a discrepancy between sexes regarding the experience of realism in a virtual environment and changes in objective behavioral measures such as voice level.
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| 37. |
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| 38. |
- Pelegrin-Garcia, David, et al.
(författare)
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Measurement and prediction of voice support and room gain in school classrooms
- 2012
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 131:1, s. 194-204
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Tidskriftsartikel (refereegranskat)abstract
- Objective acoustic parameters have been measured in 30 school classrooms. These parameters include usual descriptors of the acoustic quality from the listeners’ standpoint, such as reverberation time, speech transmission index, and background noise level, and two descriptors of the acoustic properties for a speaker: Voice support and room gain. This paper describes the measurement method for these two parameters and presents a prediction model for voice support and room gain derived from the diffuse field theory. The voice support for medium-sized classrooms with volumes between 100 and 250 m3 and good acoustical quality lies in the range between _14 and _9 dB, whereas the room gain is in the range between 0.2 and 0.5 dB. The prediction model for voice support describes the measurements in the classrooms with a coefficient of determination of 0.84 and a standard deviation of 1.2 dB.
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| 39. |
- Sjökvist, Lars-Göran, et al.
(författare)
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Modal Analysis for Floors in Lightweight Buildings
- 2007
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Ingår i: 36th International Congress and Exhibition on Noise Control Engineering (INTER-NOISE 2007 ISTANBUL). - : Curran Associates.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 40. |
- Stockfelt, Leo, 1981, et al.
(författare)
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A controlled chamber study of effects of exposure to diesel exhaust particles and noise on heart rate variability and endothelial function
- 2022
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Ingår i: Inhalation Toxicology. - : Taylor and Francis Ltd.. - 0895-8378 .- 1091-7691. ; 34:5-6, s. 159-170
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Tidskriftsartikel (refereegranskat)abstract
- Background: Adverse cardiovascular effects are associated with both diesel exhaust and road traffic noise, but these exposures are hard to disentangle epidemiologically. We used an experimental setup to evaluate the impact of diesel exhaust particles and traffic noise, alone and combined, on intermediary outcomes related to the autonomic nervous system and increased cardiovascular risk. Methods: In a controlled chamber 18 healthy adults were exposed to four scenarios in a randomized cross-over fashion. Each exposure scenario consisted of either filtered (clean) air or diesel engine exhaust (particle mass concentrations around 300 µg/m3), and either low (46 dB(A)) or high (75 dB(A)) levels of traffic noise for 3 h at rest. ECG was recorded for 10-min periods before and during each exposure type, and frequency-domain heart rate variability (HRV) computed. Endothelial dysfunction and arterial stiffness were assessed after each exposure using EndoPAT 2000. Results: Compared to control exposure, HRV in the high frequency band decreased during exposure to diesel exhaust, both alone and combined with noise, but not during noise exposure only. These differences were more pronounced in women. We observed no synergistic effects of combined exposure, and no significant differences between exposure scenarios for other HRV indices, endothelial function or arterial stiffness. Conclusion: Three-hour exposure to diesel exhaust, but not noise, was associated with decreased HRV in the high frequency band. This indicates activation of irritant receptor-mediated autonomic reflexes, a possible mechanism for the cardiovascular risks of diesel exposure. There was no effect on endothelial dysfunction or arterial stiffness after exposure. © 2022 The Author(s).
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| 41. |
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| 42. |
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- Wistbacka, Greta Öhlund, et al.
(författare)
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VOICE LEVELS IN SIMULATED ROOM ACOUSTIC ENVIRONMENTS. SEX AND AGE DIFFERENCES
- 2023
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Ingår i: Forum Acusticum 2023 - 10th Convention of the European Acoustics Association, EAA 2023. - 2221-3767. - 9788888942674
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Konferensbidrag (refereegranskat)abstract
- Vocal problems are common among workers in voice demanding occupations. For sustaining vocal health, it is important to find efficient ways to reduce strain on the voice at work. One way to do so is optimizing the room acoustics for communication. However, we do not know enough about what kind of room acoustic conditions that support voice and speech most efficiently, and if talkers of different ages and sex have different room acoustic needs. The purpose of this project was to investigate how different acoustic environments affect voice and speech in men and women aged 20-72 (N = 80). An experimental set-up was developed for acoustic and visual simulation of different room conditions, using real-time auralization of a speaker's own voice in a 64-loudspeaker array in an anechoic room combined with virtual reality. Room conditions varied in room size, reverberation time and the speaker-oriented room acoustic parameters voice support and room gain. Preliminary results show that men adapt their voice levels more to changes in acoustic conditions compared to women. No effect of age was identified. These results show that male and female talkers respond differently to room acoustic conditions, which suggest that they might not benefit equally from room acoustic improvements.
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