Acoustic absorption is the process by which the energy of a sound wave is dissipated within a material or medium rather than being reflected or transmitted onward. This occurs when incident sound waves induce oscillatory motion in the particles of a material, and part of the wave’s mechanical energy is converted into other forms of energy, predominantly heat, due to internal frictional and viscous losses. As a result, the amplitude of the reflected or transmitted wave is reduced relative to the incident wave, indicating that some of the original acoustic energy has been absorbed.
The effectiveness of this process is described by the absorption coefficient, defined as the ratio of absorbed sound energy to incident sound energy at a given frequency. This coefficient depends strongly on frequency and on the physical properties of the absorbing material, such as porosity, density, thickness, and internal structure. Porous materials allow sound waves to penetrate structures, where viscous and thermal interactions within the pores lead to energy dissipation. In contrast, dense and rigid surfaces tend to reflect more sound and exhibit low absorption.
Acoustic absorption applications such as room acoustics, noise control, and soundproofing, where controlling reverberation and reducing unwanted reflections are essential. By incorporating materials with known absorption characteristics, it is possible to tailor the acoustic response of an environment in a predictable and measurable way, consistent with established physical principles governing wave behavior.
