Explode view of an Acoustic ceiling

The good looks of crafted acoustics – and how it’s done.

Expansive visions and the desire to give each structural element a distinctive character often involve considerable practical challenges, not the least when it comes to the acoustical environment. In other words, the challenge of limiting noise and its associated health problems.

In addition to reduce noise or unwanted sounds from, for example, nearby traffic or adjacent premises which falls under Blocking in the ABC of Acoustics, you also need to address the A for Absorption and C for Cover. The challenge of absorption includes the desire to achieve good so-called speech intelligibility. Often measured as the Speech Transmission Index (STI), which is a number between 0 and 1 where 0 is poor and 1 is good. You get good speech intelligibility if you have a sound environment that enables relatively short reverberation times. Reverberation time is simply the time it takes for a sound impulse to be absorbed and disappear. The STI in such areas is generally speaking greater than 0,6.

If you are in a room or space with long reverberation times, you get the effect that the sound takes a long time to disappear. The sounds that are in the room will then “wander around” until they have ebbed out. Sounds that have been wandering around for a while can sometimes hit the eardrum at the same time as other sounds. The ear then finds it difficult to distinguish these and be able to interpret the messages, which are individually understandable but together become a murmur. The speech intelligibility is poor and the STI is low.

Often the first thing you lose is consonants and eventually you have lost so many consonants that you need to be born in a consonant-heavy part of the world to even have a chance to interpret the incoming sound. Compare with how it sometimes sounds in old stairwells.

Absorbing sound energy

To solve this problem, something is needed in the room that stops the sound from wandering around. The sound, or more correctly the sound energy, must be absorbed. For this, we need to add absorbent material. Various textiles, upholstered furniture and carpets all act as absorbents, but it can be difficult to determine to what extent these materials and furnishings absorb sound. In addition, the sound environment and along with it the STI changes if you replace some of these items or if you move them around the room.

It is both easier and more efficient to work with fixed installations as you can calculate how much absorbent material is needed and install exactly the right amount and in the right places. The ceiling is a surface that is practical to use since it is usually as big as the floor but contains significantly fewer obstacles. After all, it is quite a challenge to decorate the ceiling with furniture. As a result, the ceiling is often used to add sound absorption to the room.

Converting sound to heat

Sound is a form of energy. Energy cannot be eliminated but only converted into another type of energy. In our case, sound is converted into heat. 

Our acoustic ceiling and wall products consists of an absorbent core, which is where the absorption of sound takes place. As an absorbent core, some form of porous board is usually used, often made from rock wool, glass wool, glass granules, PE etc. These boards are seldom attractive to the eye, and the grid pattern that occurs when these boards are installed is rarely appreciated. To remedy this, you need an aesthetically pleasing, seamless surface. A surface that also must be porous enough to allow the sound energy to reach the absorbent core. We use acoustical plaster to achieve an aesthetically pleasing, seamless surface. Acoustical plaster is an acoustically transparent plaster which is sprayed on and/or hand troweled to a seamless surface.

Appealing design and porosity, however, usually counteract each other. At Styjl, we solve this by working with a very fine porosity,
which is basically invisible to the naked eye.

The result is crafted acoustics with great looks and highly efficient sound-absorbing qualities.

Styjl
Kyrkängsgatan 6
SE 503 38 Borås
Sweden
Phone +46 (0)33 430 22 00
info@styjl.com

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