scholarly journals Sound Transmission Loss of a Sandwich Plate with Adjustable Core Layer Thickness

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4160
Author(s):  
Tom Ehrig ◽  
Martin Dannemann ◽  
Ron Luft ◽  
Christian Adams ◽  
Niels Modler ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Core Layer ◽  
Constrained Layer Damping ◽  
Sound Transmission Loss ◽  
Frequency Range ◽  
The Core ◽  
Set Up ◽  
Stiffness And Damping

Compressible Constrained Layer Damping (CCLD) is a novel, semi-active, lightweight-compatible solution for vibration mitigation based on the well-known constrained layer damping principle. The sandwich-like CCLD set-up consists of a base structure, a constraining plate, and a compressible open-cell foam core in between, enabling the adjustment of the structure’s vibration behaviour by changing the core compression using different actuation pressures. The aim of the contribution is to show to what degree, and in which frequency range the acoustic behaviour can be tuned using CCLD. Therefore, the sound transmission loss (TL), as an important vibro-acoustic index, is determined in an acoustic window test stand at different actuation pressures covering a frequency range from 0.5 to 5 kHz. The different actuation pressures applied cause a variation of the core layer thickness (from 0.9 d0 to 0.3 d0), but the resulting changes of the stiffness and damping of the overall structure have no significant influence on the TL up to approximately 1 kHz for the analysed CCLD design. Between 1 kHz and 5 kHz, however, the TL can be influenced considerably well by the actuation pressure applied, due to a damping-dominated behaviour around the critical frequency.

scholarly journals Non-Wovens as Sound Reducers

2018 ◽  
Vol 55 (2) ◽  
pp. 64-76
Author(s):  
D. Belakova ◽  
A. Seile ◽  
S. Kukle ◽  
T. Plamus
Keyword(s):  
Absorption Coefficient ◽  
Surface Density ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Sound Insulation ◽  
Material Structure ◽  
Sound Transmission Loss ◽  
Sound Waves ◽  
Frequency Range

Abstract Within the present study, the effect of hemp (40 wt%) and polyactide (60 wt%), non-woven surface density, thickness and number of fibre web layers on the sound absorption coefficient and the sound transmission loss in the frequency range from 50 to 5000 Hz is analysed. The sound insulation properties of the experimental samples have been determined, compared to the ones in practical use, and the possible use of material has been defined. Non-woven materials are ideally suited for use in acoustic insulation products because the arrangement of fibres produces a porous material structure, which leads to a greater interaction between sound waves and fibre structure. Of all the tested samples (A, B and D), the non-woven variant B exceeded the surface density of sample A by 1.22 times and 1.15 times that of sample D. By placing non-wovens one above the other in 2 layers, it is possible to increase the absorption coefficient of the material, which depending on the frequency corresponds to C, D, and E sound absorption classes. Sample A demonstrates the best sound absorption of all the three samples in the frequency range from 250 to 2000 Hz. In the test frequency range from 50 to 5000 Hz, the sound transmission loss varies from 0.76 (Sample D at 63 Hz) to 3.90 (Sample B at 5000 Hz).

Functionally graded viscoelastic core characteristics on vibroacoustic behavior of double-walled cylindrical shells in a subsonic external flow

2022 ◽  
pp. 107754632110467
Author(s):  
Shohreh Reaei ◽  
Roohollah Talebitooti
Keyword(s):  
Cylindrical Shell ◽  
Transmission Loss ◽  
Excitation Frequency ◽  
Shear Deformation Theory ◽  
Sound Transmission ◽  
Functionally Graded ◽  
Loss Coefficient ◽  
Sound Transmission Loss ◽  
Polymeric Foam ◽  
The Core

The present study is concerned with an analytical solution for calculating sound transmission loss through an infinite double-walled circular cylindrical shell with two isotropic skins and a polymeric foam core. Accordingly, the two-walled cylindrical shell is stimulated applying an acoustic oblique plane wave. The equations of motion are derived according to Hamilton’s principle using the first-order shear deformation theory for every three layers of the construction. Additionally, by the aid of employing the Zener mathematical model for the core of polymeric foam, mechanical properties are determined. To authenticate the results of this study, the damping of the core layer goes to zero. Therefore, the numerical results in this special case are compared with those of isotropic shells. The results prove that the presented model has high accuracy. It is also designated that decreasing the power-law exponent of the core leads to improving the sound transmission loss through the thickness of the construction. Besides, in addition to probe some configurations versus alterations of frequencies and dimensions, the convergence algorithm is provided. Consequently, it is realized that by increasing the excitation frequency, the minimum number of modes to find the convergence conditions is enhanced. The results also contain a comparison between the sound transmission loss coefficient for four different models of a core of a sandwiched cylindrical shell. It is comprehended that the presented model has a transmission loss coefficient more than the other types of the core at high frequencies.

Experimental Study of Sound Transmission Loss in Electrorheological Liquids

2002 ◽  
Author(s):  
Marek L. Szary ◽  
Maciej Noras
Keyword(s):  
Electric Field ◽  
Sound Propagation ◽  
Transmission Loss ◽  
Active Vibration Control ◽  
Sound Transmission ◽  
Sound Transmission Loss ◽  
Frequency Range ◽  
Field Density ◽  
Active Vibration ◽  
College Of Engineering

Electrorheological (ER) liquids possess the ability to change their physical properties like the apparent viscosity and modulus of elasticity under the influence of an external electric field. They serve successfully in the field of active vibration control—as well as in many other areas. In the Acoustic Laboratory at the College of Engineering, Southern Illinois University in Carbondale, research on the possibility of applying ER liquids to the control of a sound transmission loss (STL) was conducted. The STL was investigated for various kinds of ER suspensions in the frequency range 100 Hz to 2 kHz. An influence of the electric field density on the STL was different for normal and shear stress developed by DC voltage. In both cases the STL decreased with the increasing electric field density. These properties could be potentially useful in sound propagation control applications.

Active damping of sound transmission through an electrorheological fluid-actuated sandwich cylindrical shell

2018 ◽  
Vol 22 (3) ◽  
pp. 833-865 ◽  
Author(s):  
Seyyed M Hasheminejad ◽  
Masoud Cheraghi ◽  
Ali Jamalpoor
Keyword(s):  
Cylindrical Shell ◽  
Sliding Mode Control ◽  
Transmission Loss ◽  
Sliding Mode ◽  
Sound Transmission ◽  
Core Layer ◽  
Electrorheological Fluid ◽  
Sound Transmission Loss ◽  
Mode Control ◽  
Fluid Core

An exact model is proposed for sound transmission through a sandwich cylindrical shell of infinite extent that includes a tunable electrorheological fluid core, and is obliquely insonified by a plane progressive acoustic wave. The basic formulation utilizes Hamilton’s variational principle, the classical and first order shear deformation shell theories, the Kelvin–Voigt viscoelastic damping model (for the electrorheological fluid-core layer), and the wave equations for internal/external acoustic domains coupled by the proper fluid/structure compatibility relations. The Fourier–Bessel series expansions are used to arrange the governing (coupled) system equations in state-space form. The classical Sliding Mode Control law is then applied to semi-actively reduce sound transmission through the composite cylinder by smart variation of stiffness and damping characteristics of the electrorheological fluid-core actuator layer according to the control command. Numerical results present both the uncontrolled and controlled sound transmission loss spectra of the sandwich cylindrical shell at three angles of incidence for three distinct sets of material input parameters that represent the electric-field dependency of the complex shear modulus of the electrorheological fluid-core layer. The superior soundproof performance of electrorheological fluid-based sliding mode control system in avoiding the highly detrimental sound transmission loss dips occurring throughout the critical resonance and coincidence regions is demonstrated. Likewise, remarkable enhancements in the sound insulation characteristics of the electrorheological fluid-actuated structure utilizing the first or second electrorheological fluid material model are achieved within the stiffness-controlled region, especially at lower frequencies in near-grazing incidence situation. A number of limiting cases are introduced and validity of the formulation is confirmed by comparison with the available data.

Sound Transmission Loss of Adaptive Sandwich Panels Treated With MR Fluid Core Layer

2016 ◽  
Author(s):  
Masoud Hemmatian ◽  
Ramin Sedaghati
Keyword(s):  
Magnetic Field ◽  
Applied Magnetic Field ◽  
Transmission Loss ◽  
Sandwich Panels ◽  
Sound Transmission ◽  
Core Layer ◽  
Sound Transmission Loss ◽  
Mr Fluid ◽  
Low Frequencies ◽  
Fluid Core

This study aims to investigate the sound transmission loss (STL) capability of sandwich panels treated with Magnetorheological (MR) fluids at low frequencies. An experimental setup has been designed to investigate the effect of the intensity of the applied magnetic field on the natural frequencies and STL of a clamped circular plate. A multilayered uniform circular panel comprising two elastic face sheets and MR fluid core layer is fabricated. It is shown that as the applied magnetic field increases, the fundamental natural frequency of the MR sandwich panel increases. Moreover, the STL of the panel at the resonance frequency considerably increases under applied magnetic field. Furthermore, an analytical model for the STL of the finite multilayered panels with MR core layer is developed and compared with the experimental measurements. The MR core layer is treated as a viscoelastic material with complex shear modulus. It is shown that good agreement exists between the analytical and experimental results. Parametric study has also been conducted to investigate the effect of face sheets and core layers’ thickness.

scholarly journals Analysis of the transmission loss of double-leaf panels with an equivalent spring–mass model for studs

2020 ◽  
Vol 37 ◽  
pp. 126-133
Author(s):  
Yuan-Wei Li ◽  
Chao-Nan Wang
Keyword(s):  
Distribution Curve ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Experimental Results ◽  
Sound Insulation ◽  
Sound Transmission Loss ◽  
Mass Model ◽  
Steel Stud ◽  
Panel Thickness ◽  
Stiffness Distribution

Abstract The purpose of this study was to investigate the sound insulation of double-leaf panels. In practice, double-leaf panels require a stud between two surface panels. To simplify the analysis, a stud was modeled as a spring and mass. Studies have indicated that the stiffness of the equivalent spring is not a constant and varies with the frequency of sound. Therefore, a frequency-dependent stiffness curve was used to model the effect of the stud to analyze the sound insulation of a double-leaf panel. First, the sound transmission loss of a panel reported by Halliwell was used to fit the results of this study to determine the stiffness of the distribution curve. With this stiffness distribution of steel stud, some previous proposed panels are also analyzed and are compared to the experimental results in the literature. The agreement is good. Finally, the effects of parameters, such as the thickness and density of the panel, thickness of the stud and spacing of the stud, on the sound insulation of double-leaf panels were analyzed.

Sign in / Sign up

Export Citation Format

Share Document