Helmholtz Resonator

A Helmholtz resonator is an acoustic absorber consisting of an enclosed air volume connected to the room through a narrow neck or perforated opening. It absorbs sound strongly at its resonant frequency, which is determined by the neck geometry and cavity volume. Named after Hermann von Helmholtz, these resonators can be tuned to target specific problematic frequencies, making them invaluable for controlling room modes and low-frequency buildups. In practice, Helmholtz resonators appear as perforated panels over air cavities, slotted wall systems, and purpose-built bass absorbers. Adding porous material inside the cavity broadens the absorption bandwidth at the expense of peak absorption efficiency. Arrays of differently tuned resonators can provide broadband low-frequency control. Helmholtz resonators are widely used in auditorium design, recording studios, and industrial noise control applications.