Maro PULJIZEVIć’s scientific contributions

Sound absorption coefficients are among the most important acoustic parameters of building materials. The coefficients are measured in reverberation chambers using the ISO354 measurement procedure. The complex reverberant sound field that builds up in such facilities is closely related to the concept of the diffuse sound field and is difficult to characterize experimentally. Due to the limited quantitative assessment of the sound field, there is no general agreement in the scientific community on how to improve the method of measuring sound absorption coefficients, although significant differences have been reported between the results of different laboratories. To address part of this challenge, we investigate how specific the variations between laboratory results are for a particular material. In our investigation, we evaluated four different sound absorbing materials in five independent acoustics laboratories. Four of the reverberation chambers used suspended diffusers, while the complex shape of one chamber was designed to achieve a diffuse sound field. The results show that the interlaboratory deviations are not very specific to the material tested, while general differences between the facilities can be observed. Furthermore, the meticulous geometric design of the chambers can be seen as an alternative to the use of suspended diffusers.

This paper presents a comprehensive investigation into the differences observed when evaluating the acoustic properties of a multi-layered material using different standardized methods. The primary focus is on the membrane effect of the upper aluminum layer, which has been shown to contribute to the overall acoustic absorption. This phenomenon, crucial for applications requiring enhanced acoustic performance at lower frequencies, is observed in tests conducted with large sample sizes but remains undetected in impedance tube measurements. Through a series of experiments, including reverberant chamber, impedance tube, and in-situ absorption measurements, this study investigates the complexities of accurately estimating sound absorption characteristics in multi-layered materials. Additionally, 2D colormaps to visualize the spatial distribution of sound absorption across different samples are examined, offering deeper insights into the uneven absorption patterns that standard testing methods may overlook. The experimental findings highlight the importance of selecting an appropriate evaluation technique for multi-layered materials, particularly in applications where acoustic performance is critical at lower frequencies.