Analysis of Sound Transmission Loss of Double-Leaf Walls in the Low-Frequency Range Using the Finite Element Method

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).

The Role of Studs in the Sound Transmission of Double Walls

“…3. In Section 4.4 these results are used as input data in SEA models and in Section 4.5 the whole vibroacoustic problem is solved by means of the finite element method or a combination with modal analysis [11,12,13]. Note that to characterise the stud, both the simplified and detailed models have to be solved.…”

“…This simplification is even more relevant when the analysed structure is a double wall. In [13] the rooms are described by means of modal analysis and the double wall using finite elements. The connection between leaves is done by means of plane homogeneous plates.…”

A modal-spectral model for flanking transmissions

“…Analytical modal expansion of the pressure field in cavities is a good option when: i)the shape of the domains to be studied is simple but the dimensions large; ii)the computational costs must be optimised at maximum; iii)it is important to cover a wide frequency range to gain knowledge on the physics of the problem and iv)the coupling is weak enough in order to consider the in vacuo modes of each sub-domain of the problem. This technique, recently reviewed in [15], has been considered in the study of a cuboid-shaped cavity coupled with a rectangular plate [16,17,18], the sound transmission between cuboid-shaped rooms separated by: a single wall [19,20,21,22,23,24,25,26,27], a double wall [28,29], cavities of double walls [30], slits and holes [31] or the transmissions between continuous plates coupled to rooms [32]. Other models combine a modal description in one plane with a description in function of plane waves propagating in positive and negative direction normal to the modal plane which helps in order to impose the continuity of normal velocity.…”

Parametric uncertainty quantification of sound insulation values

“…7 Deterministic models have been employed for investigating the influence of individual parameters independently and without measurement errors, mainly at low frequencies. [8][9][10][11][12] From these studies, it was found that many parameters have a considerable effect on the direct sound insulation, also when only variations that are compatible with recent building acoustics standards are considered. These include parameters that are related to the measurement setup (number of microphones and their configuration, sound sources, averaging strategy), the partition (dimensions, boundary conditions, damping), and the rooms (dimensions, geometry, uniform and localized acoustic absorption).…”