Modern airplanes use acoustic panels with Helmholtz resonators to damp out engine noise. Multi Helmholtz Resonator -Subwoofer Traditional Subwoofer applications have had one helmholtz resonator for each cone surface,max. The margin for design or constructional error, therefore, is minimal.

Figure 1 Helmholtz established the following equation to describe the resonant frequency of a cavity: The theory of Helmholtz resonators is widely used in exhaust systems for internal combustion engines and loudspeaker systems (especially ported speakers and subwoofers). A Helmholtz resonator or Helmholtz oscillator is a container of gas (usually air) with an open hole (or neck or port). Audiophiles and recording studios use slat resonators to “trap” undesirable frequencies. A common example is an The Helmholtz resonator is commonly applied to musical instruments but is also found as automobile mufflers and subwoofers. In most of the subwoofers, only one surface has been loaded with helmholtz resonator, while some of them have sixth order bandpass configuration and load both cone surfaces with resonator. A volume of air in and near the open hole vibrates because of the 'springiness' of the air inside. The Helmholtz resonator is a narrow-bandwidth device, designed and used to target specific single frequency anomalies. One area often overlooked is that of port end-correction, without which a design may be rendered ineffective.