A fabric can tick all of the boxes acoustically

Did you know that although fabric can tick all of the boxes aesthetically, it might not have properties that are conducive to being used for acoustic panelling?

Nowadays, the focus of acoustic panelling is becoming more balanced between ‘function’ and ‘aesthetics’. Solving acoustic problems can be done in an aesthetically pleasing way and sometimes the acoustic treatments can become the design focus of room interiors.
When choosing fabrics it is best to choose ones that have an open weave and are breathable. Be careful not to choose a fabric that has too much of an open weave, as you do not want to be able to see the core material through the fabric. Get this wrong and the absorption performance can be dramatically reduced.
Fabrics have weaves that create pores with different sizes and shapes, and with their different thermal and viscous effects, they influence the sound waves passing through them changing the absorption values. Fabrics are available ‘backed‘ or ‘unbacked‘. Backed fabrics are lined one side with either paper or acrylic, normally to assist with direct wall applications. Fabric used with acoustic panelling systems is usually ‘un-backed’ as backed fabrics do not stretch well.

There are three types of absorbers: porous absorbers, membrane absorbers, and resonance absorbers. Porous absorbers, fuzzy fibrous materials like carpet, decrease sound pollution in the environment by allowing sound transmission to occur in such a way that the fibres rub together and cause the acoustic energy to be converted to heat. As the sound energy penetrates the material the sound-absorbing effect is obtained and as the required thickness is large with porous textile absorbers, obtaining adequate absorption at low frequencies is more difficult and requires great thickness.

Membrane absorbers take many shapes and comprise a membrane that resists movement from the sound energy causing a reduction in energy and resultant absorption. There are box versions where air is trapped behind the membrane as a spring creating some tuning and often extending the low frequency absorption.

Resonance absorbers, referred to as Helmholtz absorbers are resonant boxes that have an aperture to admit the sound – they work by taking the sound, resonating and re-emitting the sound such that much will be in an opposed phase and cancel the next approaching sound wave.

Designs can use a mix of types and performances to deal with the needs of a room. Acousticians need the data about frequency-dependent sound absorption and flow resistance in order to work out the acoustics for the room, which types will be best and arrange them so they work with the natural behaviour of the room, and then cover all this up with fabrics.