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Acoustic excitation and transmission of lightweight structures

Brunskog, Jonas LU (2002) TVBA-1009.
Abstract (Swedish)
Popular Abstract in Swedish

För att öka förståelsen för hur ljud sprider sig och strålar från byggnadskonstruktioner utförda i lättbyggnadsteknik så behövs teoretiska beräkningsmodeller. Sådana modeller presenteras i avhandlingen. Med lättbyggnadsteknik avses konstruktioner som inte är massiva, exempelvis väggar och bjälklag bestående av trä- eller stålreglar/bjälkar. Stegljudet, det vill säga det ljud vi hör när våra grannar går på sitt golv, är speciellt svårt att handskas med när man bygger med lättbyggnadsteknik. En stor del av avhandlingen ägnas därför åt detta. Speciella detaljaspekter som hur bjälklagen exciteras och hur oregelbundenheter påverkar responsen ges särskild uppmärksamhet.
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... (More)
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. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Mace, Brian, ISVR, Southampton, UK.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
point mobility, Lamb waves, wood., Building construction, plate excitation, cavities, near-periodicity, nearly periodic, sound insulation, timber, structural acoustics, spatial Fourier transform, resilient device, prediction model, periodic, lightweight, ISO tapping machine, airborne noise, Building acoustics, impact noise, Byggnadsteknik
volume
TVBA-1009
pages
196 pages
publisher
Div. Engineering Acoustics, LTH
defense location
Room V:B, V-building, LTH, John Ericssons väg 1, Lund
defense date
2002-12-13 13:15
external identifiers
  • other:ISR:LUTVDG/(TVBA-1009)/1-196/(2002)
ISSN
0281-8477
ISBN
91-628-5474-7
language
English
LU publication?
yes
id
e9a80478-125c-49ac-8ce0-c62154d9fa10 (old id 465296)
date added to LUP
2007-09-06 13:06:16
date last changed
2016-09-19 08:44:56
@phdthesis{e9a80478-125c-49ac-8ce0-c62154d9fa10,
  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.},
  author       = {Brunskog, Jonas},
  isbn         = {91-628-5474-7},
  issn         = {0281-8477},
  keyword      = {point mobility,Lamb waves,wood.,Building construction,plate excitation,cavities,near-periodicity,nearly periodic,sound insulation,timber,structural acoustics,spatial Fourier transform,resilient device,prediction model,periodic,lightweight,ISO tapping machine,airborne noise,Building acoustics,impact noise,Byggnadsteknik},
  language     = {eng},
  pages        = {196},
  publisher    = {Div. Engineering Acoustics, LTH},
  school       = {Lund University},
  title        = {Acoustic excitation and transmission of lightweight structures},
  volume       = {TVBA-1009},
  year         = {2002},
}