The acoustic behavior of concrete resonators incorporating absorbing materials

Acoustic resonators are a common engineering solution providing sound absorption in intermediate frequencies. They are used in many acoustic applications where noise absorption is required, such as outdoor barriers. Outdoor noise barriers face aggressive weather conditions and so their design has to reconcile durability and absorption. This compromise may be achieved by making use of materials such as standard and lightweight concrete. The work described in this paper analyzes the acoustic behavior of concrete resonator shapes using an experimental approach. The resonant frequency of resonators of different dimensions and the sound absorption they provide are determined. In addition, lightweight concrete resonator-like structures are analyzed, and their acoustic absorption is characterized. Mixed devices that incorporate both standard concrete, lightweight concrete (with expanded clay) and porous materials, arranged in different configurations, are also analyzed so as to define higher performance solutions.