The acoustic sealing of holes and slits in walls

doi:10.1016/S0022-460X(86)80163-8

Journal of Sound and Vibration

Volume 111, Issue 2, 8 December 1986, Pages 297-336

https://doi.org/10.1016/S0022-460X(86)80163-8 Get rights and content

The sound transmission through circular holes and through long slits in a wall of finite thickness is computed for oblique plane waves. These openings may be filled by porous absorber materials and/or they may be sealed at their end planes by plastic sealing layers. The absorber materials are modelled by their acoustic characteristic data (propagation constant and wave impedance) and the sealing layers are represented by masses. The analysis is treated as a boundary problem. The final quantities are the transmission coefficient or the transmission loss. Numerical results show the influence of the design parameters. It is found that the performance of openings with a porous and/or plastic sealing cannot be approximated by the results for empty and open holes or slits. As a result of these studies it is recommended to use a transmission loss of the hole reduced by its cross-sectional area and to use a transmission loss of the slit reduced by its width as the final quantities, once the sound transmission through such openings should be standardized. These reduced transmission losses are nearly independent of the area under most conditions of parameters and frequency.

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Study on sound insulation performance of double-layer perforated panel under normal incidence waves
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Then the acoustic end correction formula of perforated panel was computed at different porosities by the finite element numerical simulation method [9], which was still used to calculate the transmission loss. The research on the sound insulation performance of perforated panel started from Refs. [10–12], which carried out the prediction of TL of perforated panel and slit. Vigran [13] extended the research to the influence of the shape change of the hole and slit.
Based on the single-hole model, the sound insulation performance of four perforated panel structures were studied, including single-layer perforated panel, double-layer perforated panel, double-layer through-hole panel and double-layer resonant panel. Based on the plane wave theory, a modified transfer matrix method (MTM) was developed to improve the accuracy of traditional transfer matrix method (TM). For MTM, acoustic length corrections were used to modify the transfer matrix to consider the influence of multi-dimensional waves. Then MTM was used to predict the transmission loss (TL) of the four perforated panel structures, and the results were compared with those of the finite element method (FEM). The comparison showed good agreement in the effective frequency range. Using the MTM, the effects of dimensions on the TL of the four perforated panel structures were studied. The double-layer perforated panel can significantly increase the TL at the medium and high frequencies, and the double-layer resonant panel structure can increase the TL at the low frequency because of the resonance. In addition, the TL amplitude is influenced by the opening ratio, which decreases rapidly with the increasing of opening ratio. The thickness of the panel and the spacing between the two layers can mainly change the width of the high absorption region. The parameters of the resonant neck can change the resonant frequencies and pass-by frequencies. Finally, the predictions of MTM are verified with the experimental results of double-layer perforated panel sample. The method in this paper can be used to design the perforated panel structure for sound insulation.
The acoustic performance of circular openings and wall-mounted vents
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Outdoor air intakes (vents) adversely affect the sound insulation of a building envelope. The purpose of the research was to investigate how different components of the wall-mounted vent and the vent-wall geometry influence its acoustic performance, and to provide practical guidelines that can be used in the design and testing of such devices. The study is based on laboratory measurements. Three basic questions are discussed: the test facility, the effect of a circular opening in a wall and the performance of a vent installed in the opening. A double partition wall should be used in the laboratory to suppress flanking transmission and provide reliable results. Low frequency modal effects related to a sample position in the wall did not influence the single number quantities. Circular openings exhibited fundamental resonance depending on the wall thickness, the diameter of the opening and the end reflection conditions. These effects contributed to the sound transmission loss of a complete vent. The vent components are effective mostly at high frequencies, as low frequency bands are controlled by the wall, while the improvement of middle frequencies is still a challenge. Aside from resonance, the combined sound insulation of particular vent components was approximately the same as that of the complete integrated unit.
A study of the sound transmission mechanisms of a finite thickness opening without or with an acoustic seal
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Citation Excerpt :
The resultant curve is depicted in Fig. 2. Also shown in the figure are the TL curves calculated by using the models of Soroka [10] and Mechel [16]. Good agreement can be found among the three curves across the entire frequency range of interest, indicating the capability of the model in predicting the sound transmission loss of an empty opening of small cross-sectional area.
This work is concerned with the transmission of sound through an opening in a wall of finite thickness where the opening may be filled with an acoustic seal represented by a pair of mass layers. Unlike past work where efforts were made on either developing a prediction model or investigating the influence of opening parameters on the sound transmission performance, the work presented here aims at studying the coupling mechanism of the system by considering the fluid-loaded opening as a resonant system. This treatment allows a better understanding of the system property at both resonance and off-resonance frequencies. It is found that, unlike that for the opening of vanishing thickness, the transmission loss for an opening of finite thickness exhibits obvious oscillation with maxima and minima in the frequency spectrum. The latter are associated with the resonance of the fluid-loaded opening. At resonance, the opening extracts the acoustic energy from a region much larger than its physical dimension, causing more energy to transmit through the opening. As a result, negative value of transmission loss occurs. At frequencies off the resonance, the way in which energy flows into the opening is found to be dependent upon the reactance of the wave impedance of the fluid-loaded system. For a sealed opening, the reactance of the wave impedance is greatly increased due to the large surface density of the mass layers of the acoustic seal, resulting in less energy injected into and thereby transmitted through the opening. The underlying physics leading to the improvement in sound insulation is sought by using a wave impedance expression from which equivalent system representation is derived in different frequency ranges.
Active control of sound transmission through a floor-level slit
2023, Journal of the Acoustical Society of America
Investigation of HVAC Kinematics Mechanism & Door Noise through Acoustical Duct Method
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View full text

The acoustic sealing of holes and slits in walls

Journal of Sound and Vibration

The “sound insulation” of circular and slit-shaped apertures

Acustica

The influence of viscosity on sound transmission through small circular apertures in walls of finite thickness

Acustica

The sound transmission loss of circular and slit-shaped apertures in walls

Acustica

Comments on “Approximation to the diffraction of sound by a circular aperture in a rigid wall of finite thickness”

Journal of the Acoustical Society of America

Approximation to the diffraction of sound by a circular aperture in a rigid wall of finite thickness

Journal of the Acoustical Society of America

Reply to “Comments on ‘Approximation to the diffraction of sound by a circular aperture in a rigid wall of finite thickness’”

Journal of the Acoustical Society of America

On the transmission of acoustic waves through a circular channel of a thick wall

University Research Institute of Electrical Communication Report

Schalldämmung von Fugen mit porösen Dichtungsstreifen

Die Schalldämmung von Fugen-Möglichkeiten ihrer Verbesserung

IBP-Mitteilung Nr. 41 Institut for Bauphysics Stuttgart