Acoustic Filter Elements

There are a number of different types of acoustic filter elements that are used in many different applications.

Absorptive Duct

Absorption within ducts is used to break up standing waves and attenuate high frequency noise such as flow generated noise.

Expansion Chamber

The expansion chamber can be considered as a simple low pass filter.

Helmholtz Resonator

It is effectively a mass on a spring (single degree of freedom system). The large volume is the spring and the volume of air in the neck is the mass.

Porous Duct

A number of different types of porous materials are used within engine air intake systems to break up standing waves that would exist in a solid wall construction.

Quarter Wave Tube

A resonator used most commonly on air intake systems to reduce resonance. Works over a narrow frequency range, i.e. used to attenuate a specific frequency.

Side Branch Orifice

The side branch orifice is an acoustic filter element and behaves as a high pass filter.

See also: Acoustic Impedance, Duct Acoustics, Expansion Chamber, Helmholtz Resonator, Insertion Loss, Quarter Wave Tube, Side Branch Orifice, Silencer.