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The impact of mechanical connections between two plates on sound transmission is well-known. However, there is still a need for thorough scientific investigation into this phenomenon. Analyzing the influence of mounting elements on sound transmission can lead to effective reduction of sound propagation and improvement of partitions' sound insulation. The complexity of studying impact sound transmission through junctions arises from the various methods of connecting two parallel plates. Factors such as the number and arrangement of connecting elements, as well as the use of line or point connectors, can significantly affect sound transmission between a massive and lightweight plate. This study focuses on the influence of stud elements and the number of connecting points on the lightweight plate. An impact hammer was used to excite the massive plate, and frequency response functions were calculated for several points on both plates. The results were analyzed and compared to the theoretically derived transmission function for the investigated structure. [ABSTRACT FROM AUTHOR]

The increasing popularity of acoustic absorbing metamaterials is followed by the performance problem formulation on the type of elemental acoustic cells used for structure development. The state-of-the-art investigation provided replication problems with common designs and great dispersion in the received results compared to the references, especially on the connection methods between basic metamaterial elements and their shape modification. There is a lack of basic knowledge on the consequences of using basic metamaterial cells typology and a description of its influence and interaction between the resonators. The paper will present the numerical modeling results in COMSOL Multiphysics for the basic metamaterial cells comparison under the sound absorption coefficients - Helmholtz resonators series or quarter-wavelength resonators. Different methods for resonator placement and construction will be discussed. The analysis will cover the possible pipe or cavity bending conclusions for the construction of complex metamaterial structures. [ABSTRACT FROM AUTHOR]

Cavity-based metamaterials are usually designed for sound absorbing or sound scattering properties. They are built of combinations of ducts and slits, which in the case of acoustic absorbers are designed to maximize the sound absorption at resonance frequencies through the appearance of the viscothermal losses. The unit cells are designed under the assumption of perfectly rigid walls, shared by all the analytical models. Sound absorbing properties of the structures result from viscothermal losses in small ducts. The paper discusses the influence of adding sound absorption to the walls in the numerical model on the results of the observed sound absorption coefficient. It is demonstrated that the resulting sound absorption of the structure varies with changing sound absorption coefficient of the walls of the structure. The same observations are made for 3D-printed measurement samples, showing the importance of including the sound absorption of the walls in the modelling process. [ABSTRACT FROM AUTHOR]