How upholstery can complement the acoustic performance of a sound absorbing screen

20th Jul 2021

How upholstery can complement the acoustic performance of a sound absorbing screen

The circulation of sound within a room can be rightfully assimilated to the dispersion and refraction of light, where intensity and absorption are influenced by both surfaces, as well as the space partitioning. Blinds, as well as various translucent screens are used to control light, either by adjusting its intensity, or by redirecting its distribution. As comfort also encompasses acoustics, the quality of time experienced in a room could benefit from devices that operate under the same system for background noise and echoes.

Adjusting sound requires minimising noise, eliminating reflection, as well as enhancing acoustic clarity by neutralising echoes. Devices which can be integrated in an interior for sound absorption such as divider screens or ceiling panels should not only be considered by thickness or composition, but also by coating.

The role of fabrics in acoustic performance

Upholstery is not only introduced for aesthetic reasons. Alike foam, upholstery falls in the category of porous absorbers which dissipate acoustic energy under viscous and thermal effects. Transparency remains its fundamental feature when considered for acoustic screen coatings. While on a general basis, describes permeability in relation to air, when evaluating acoustic performance, transparency carries the role of preventing sound reflection. Reflection should be understood as the phenomenon correlated with an incomplete acoustic absorption, under which residual sound waves ricochet back into the room. Sound waves would eventually lose all their energy under the impact with other surfaces. However, when repeated, reflection can lead to reverberation which is further perceived by the human ear as echo. In order for an acoustic screen to fulfill its purpose, sound waves must easily pass through the upholstery to be absorbed by the filling. If random fabrics are introduced without a cautious scrutiny of acoustic properties, coating might block the effectiveness of the filling.

Measuring acoustic transparency

Acoustic properties in fabrics are tested by using the ISO 10534 Part 2 standard. The methodology involves applying the fabric over a 10cm thick layer of sound absorbing foam. The coating’s efficiency is calculated in contrast to the quality ensured by the foam when left isolated, as the purpose of the tests is to verify to that extent the fabric will complement the performance of a sound absorbing filling in an acoustic screen. Findings may reveal two possible scenarios. The first one indicates sound waves passing through the fabric to be absorbed by the foam. The second one confirms them being partially absorbed by the fabric before reaching the foam. The highest degree of acoustic transparency is noted, for example, in loudspeaker coverings.

Understanding Acoustic Performance

Manifesting a change of pressure in its host medium, sound is characterised by two fundamental coordinates: volume, which is expressed in decibels (dB) and tone, which is correlated to frequency and measured in Hertz (Hz). Frequency indicates the number of sound waves produced within a time frame. In their standard composition, porous absorbers are confirmed effective for mid-to-high frequency sounds. However, screen coating fabrics may be engineered for higher efficiency to different frequencies within this range. When it comes to human comfort, acoustic transparency becomes more important for panels introduced in environments challenged by high frequencies. Contrary to auditoriums or events venues, open layout offices for which acoustic screens are usually designed are not as disturbed by high frequency sounds, as they are of volume, or loudness. Even the usual conversations between colleagues which are generally mentioned as the most disruptive background noise within an office environment do not reach high frequencies. Consequently, volume, or loudness remains the main focus point when selecting acoustic screens. On such grounds, the absorbed sound level or the acoustic comfort guaranteed in decibels is usually mentioned within the technical specifications.