Experimental and analytical investigation on sound transmission loss of cylindrical shells with absorbing material
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Sound transmission class
Transmission loss
The present study focuses on a silencer built within the thick portion of a door edge and reports on the results of evaluating silencers by determining sound transmission loss via theoretical analysis and experiments on three types of silencers. The theoretical analysis involved determining the calculated values of sound transmission loss obtained using the transfer matrix method. The change in cross-sectional shape was analyzed by elemental division of the transfer matrix. Using the above, simulations were performed with respect to the optimum shape of the silencer. These theoretical analyses were then compared with the measurement results. Furthermore, the study includes the results of an experiment that attempted to restrain the dip in sound transmission loss by adding a non-woven fabric to the opening of the silencer. In a side branch silencer with an increasing shape wherein the longitudinal cross-section is a linear or an exponential function, the peak of the transmission loss was shifted to the lower frequency side when compared with that in the case of a rectangular side branch silencer. Furthermore, in comparisons between the two, the sound attenuation peak frequency was lower in the case of the exponential shape. The resonance of the side branch was suppressed by adding a non-woven fabric to the opening of the side branch silencer. As a result, the peak and dip of sound attenuation were alleviated, and the sound attenuation characteristics could be adjusted.
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Transmission loss
Sound transmission class
Acoustic attenuation
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Sound transmission loss through triple-walled sandwich cylindrical shells in the presence of an external mean flow is analytically examined. Love's theory and a simplified method based on Biot's theory are considered to describe the motions of thin isotropic shells and wave propagation in the porous material cores, respectively. The random incidence transmission loss in a diffuse field is calculated numerically by considering the limiting incidence angle due to the total internal reflection. The analytical model and numerical code are validated against both experimental and analytical results reported by previous studies. The transmission loss of triple-walled structure in the diffuse sound field is compared with its double-walled counterpart at the same weight. The results generally show a superior performance in the sound insulation for the triple-walled shell, considerably at mid-high and high frequencies, in comparison with its double-walled counterpart at the same weight. The effects of sandwich shell configuration and air gap depth are also investigated on the sound transmission loss.
Transmission loss
Sound transmission class
Biot number
Soundproofing
Limiting
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The work to be presented is part of a large series of measurements studying sound transmission through double panel walls. The wall surfaces in this work were of 16-mm gypsum board. Studs of 38-×89-mm wood or 90-mm light steel were used with spacing between stud centerlines varying from 30 to 120 cm. The spacing between screws used to attach the gypsum board was varied with the smallest separation used being 20 cm. Transmission loss was also measured for studless constructions. Transmission loss contours showed prominent dips at frequencies influenced by stud and screw spacing. Sound absorbing material added to the cavity had only a minor effect on these resonances suggesting that they are associated with panel resonances and not with the cavity between the panels. A selection of the data from this work will be presented and discussed.
Sound transmission class
Transmission loss
Structural acoustics
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Abstract Authors present a study on transmission loss and absorption of corrugated PVC panels. Tests were conducted in reverberation room and it has been proven, both theoretically and experimentally, that there is a relationship between the panel type and its transmission loss and absorption. Panel size and thickness was also taken into consideration during testing procedure. Analyses also show that the Hansen model was not perfectly accurate when predicting the transmission loss for some of the tested samples.
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Transmission loss
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In the present work, the sound transmission through a cylindrical shape acoustic enclosure is predicted analytically and verified experimentally. An analytical model is developed, based on the statistical energy analysis (SEA) approach, to examine the transmission loss of a cylindrical acoustic enclosure in different frequency regions, including the low-, intermediate-, and high-frequency ranges. In the developed model, the nonresonant wave response is included in addition to consideration of the resonant response for obtaining more accurate results. It is demonstrated that the developed SEA formulation in this work can compute the resonant as well as the nonresonant sound transmission of the cylindrical acoustic enclosure separately. To validate the analytical model, an experimental setup was developed, and the sound transmission loss of a cylindrical acoustic enclosure was measured using the sound intensity experimental technique. It was found that the analytical results are in good agreement with the measured transmission loss, especially at the panel ring and critical frequencies. The results obtained indicate that the proposed analytical model is efficient to predict the sound transmission loss of cylindrical acoustic enclosures.
Enclosure
Statistical energy analysis
Sound transmission class
Transmission loss
Sound energy
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A reconsideration of a previous study of the transmission loss of sandwich panels is presented. An erroneous calculation of the transmission loss is corrected, and new results are presented. Also, some interesting implications for the design of walls of high transmission loss are pointed out. Subject Classification: [43]55.75.
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Transmission loss
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T-junctions exist between walls and between wall and floor within the building structure,its sound transmission theory is different from transmission through the panels or slabs.So,the calculation of its sound transmission coefficient is one of the keys to predict the sound transmission through whole structure and flank transmission.In this paper,the study on the sound transmission through T-junction and measurement is presented,furthermore,the approaches how to improve sound insulation are also discussed here,that is,the better sound insulation should be obtain by adjusting the thick ratio between plates in the junction.
Sound transmission class
Soundproofing
Transmission coefficient
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Results of the measurement on sound insulation of a few partition walls are presented. The sound insulation has been measured in the transmission-reverberation chamber of this Institute. The results are compared with theoretical predictions. A simplified method is adopted to obtain approximate theoretical values of the transmission loss (T.L.).Three types of partition walls, a solid brick wall, brick cavity wall and a double wall plywood panel have been tested. The experimental values of transmission loss of the brick cavity wall is found to be lower than the computed values. This is due to sound transmission through the wire-ties bridging the two panels. The transmission loss of a single thin panel of plywood is too low to meet the insulation requirements. Sound insulation of such panels can be increased by using two panels with a little air space in between. An absorbent material loosely filled in the cavity further improves the transmission loss.
Transmission loss
Soundproofing
Sound transmission class
Brick
Cavity wall
Dynamic insulation
Electromagnetic reverberation chamber
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Transmission loss
Sound transmission class
Soundproofing
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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. Aparametric 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).
Sound transmission class
Transmission loss
Soundproofing
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