Resonant Absorber

A resonant absorber is any absorption device that works by resonating at specific frequencies, converting acoustic energy to heat through the vibration of a membrane, the oscillation of air in a neck (Helmholtz), or a combination of both. Resonant absorbers provide targeted low-to-mid frequency absorption where porous absorbers are inefficient. They are characterized by a tuning frequency (maximum absorption), a bandwidth (Q factor), and a peak absorption coefficient. Narrow-band resonant absorbers (high Q) address specific room modes, while broad-band designs (low Q, achieved by adding damping) provide more general bass control. Common types include membrane/panel absorbers, perforated panel systems, and slotted resonators. In concert hall design, tuned resonant absorbers are embedded in walls and ceilings to control low-frequency reverberation without affecting mid-to-high frequency clarity.