Developing wideband acoustic absorbers in interior spaces: modelling, measurements and applications

Abstract

This study aims to develop wideband acoustic absorbers in interior spaces for speech purposes, through the use of Micro-Perforated Panels (MPPs) arranged in different configurations. The research has involved theoretical modelling, measurements, and applications in interior spaces. The initial phase focused on modelling various MPP arrangements and predicting their sound absorption coefficients using the Electric Equivalent Circuit Model (ECM) under normal and oblique incidence conditions. Small samples with different geometric parameters were then manufactured and tested for their absorption coefficients at the Turkish Standards Institute, following the impedance tube method (ISO 10534-2:1998). The preliminary results showed a good agreement with the numerical predictions. Furthermore, the random incidence absorption coefficient of a parallel arranged MPP structure was measured in a Small-Scale Reverberation Room (SSRR) at Bilkent University to evaluate the proposed structure in a diffuse field. The results obtained by using ISO 354:2003 showed lower values than the predicted ones by a range of 0.1- 0.3. However, there was a better alignment between the ECM predictions and experimental results for 30-degree oblique incidence. Regarding interior applications, a classroom with poor acoustics was treated in ODEON 16 using the proposed material in the form of a wall panel. The effect of the developed material on objective room acoustics parameters was examined, revealing improvements in the Reverberation Time and Speech Intelligibility Index values. Lastly, the Turkish versions of Perceived Affective Qualities outlined in the ISO/TS 12913-2:2018 standard were developed to assess the subjective perception of the material following the soundscape approach.