Acoustic slatted systems

What are acoustic slatted systems?

Acoustic slatted systems absorb sound and help control the sound reverberation within spaces. They come as walls or ceiling systems and generally include the following:

Slats on a layer of felt. Some systems just have these two elements that you either screw, nail or glue to a hard surface. In this case, the felt is the main sound absorber and has a certain thickness. Otherwise, it is just a couple of millimeters thick.

Other systems include a (metal) frame to create a void with;

a sound absorber, which is usually a fibrous material.

General configuration of acoustic slatted systems

Manufacturers offer a large variety of aesthetic designs including timber species, varnishes, lacquers, prints or even colors.

Although straight slats regularly spaced is the main design theme, you can also find other (more bespoke) designs such as barcode, curved or wave effects.

Note 1: most suppliers also have the options for slatted systems with a very low sound absorption performance (i.e. with no fibrous material behind). In this case, you can purely use them as interior design finishes to bring a certain type of ambiance to the space.

Note 2: these systems have a certain thickness (especially if you mount them on a frame), so you need to plan for some space on the wall or your ceiling

What materials do acoustic slatted systems involve?

Acoustic slatted systems involve various materials that influence the aesthetics and the physical properties of the systems.

The slats

Most manufacturers make the slats with solid timber. Examples of wood species are pine, oak, spruce and douglas fir.

Others prefer using Medium-Density Fibreboard (MDF) or even fibre reinforced gypsum that increases resistance to humidity and/or impacts. See below in the interesting benefits.

The felt

Wool is the material of choice for the felt (visible behind the slats).

The frame

Although manufacturers use metal as the main material for the frame (to hold the slats together), they also use timber for some of the systems.

The fibrous sound absorber

Efficient fibrous absorbers are stone, mineral or glass wool.

Note: Manufacturers generally outsource this material from a specialist supplier.

What are the sound absorption characteristics of acoustic slatted systems?

Like for any system directly fixed to a hard surface, acoustic consultants specify the area the systems should cover.

Specification of acoustic slatted panels in surface area covered

Acoustic slatted systems achieve performances that range from sound absorption Class D up to Class A.

The performance depends on the system configuration and the materials involved.

The fibrous sound absorber in the cavity

The fibrous material is the main sound absorber sound in acoustic slatted systems.

In order to ensure a certain efficiency, it is generally 20 to 45 mm thick with a minimum density (that greatly varies depending on the material type).

As any fibrous absorber, it is very good at absorbing sound at medium and high frequencies. You can improve the sound absorption at low frequencies by adding and/or increasing the cavity behind the slats.

Note: low frequencies are 250 Hz and below, medium frequencies range are around 500 – 1000 Hz, and high frequencies are 2000 Hz above.

Sound absorption of acoustic slatted systems (Laudescher LINEA SWELL) with and without mineral fibre (with: fabric LAU 301 + 45 mm of mineral wool + 400 mm plenum; without: fabric LAU 301 + 400 mm plenum)

The spacing between the slats

Slats are not acoustically transparent. Meaning, the higher the slats concentration, the less sound reaches the fibrous absorber behind, the less the sound absorption of the system.

Therefore, manufacturers work out a slat spacing (or open area) that lets enough sound through, whilst maintaining other desired aspects such as visual aspect or impact resistance.

Influence of slat spacing on the transmission of sound

The graph below shows the sound absorption of systems with different slat spacings.

Sound absorption of acoustic slatted systems (Gustafs Linear Ribs) with different slat spacings 12 mm and 62 mm (with 200 mm void and 45 mm mineral fibre inside)

The size of the cavity behind

As mentioned above, the fibrous absorber behind the slats is the main absorbing material. Therefore, the sound absorption characteristics of the slatted systems will be very similar to that of the material.

The consequence is that slatted systems are good at absorbing sound in medium to high frequencies because fibrous absorbers are too.

However, there is an exception: the cavity between the slats and the hard surface behind can increase the absorption at low frequencies. The effect depends on the size of the cavity.

See the graph below showing the sound absorption of systems having different cavities.

Sound absorption of acoustic slatted systems (Gustafs Linear Ribs) with differentcavities 17 mm and 215 mm (with 15-17 mm mineral fibre and 12 mm slat spacing)

Do acoustic slatted systems have any other interesting physical benefits?

Acoustic slatted systems can be impact resistant, enough to install them in sports halls for example.

With the right material, the right finish and the right treatment, they can also be installed in environments with humidity levels such as outside (in sheltered areas) or in swimming pools.

Finally, most systems are (physically and aesthetically) flexible to be curved and follow the profile of the hard surface behind. Usually, this hard surface is a wall.