Whether open-plan offices, concert halls or auditoriums – building and room acoustics not only represent an important quality feature for buildings, they also significantly determine the well-being of the users.

Where previous measures for sound insulation were considered incompatible with the desire for ideal temperature control of buildings, Weiss Raised Floor Systems, a long-established company from the south-west of Germany, presents a product that makes it possible to combine both criteria: the acoustic raised floor panel.

The aim of the room acoustics of a building is an acoustic quality adapted to the room specifications and planned use of it. Considered here are aspects such as noise insulation, reverberation time, speech intelligibility or sound character.

Since the prevailing conditions in a building, in addition to the impact on the acoustic impression, also affect the well-being and health of users, the search for functional, economic solutions has become increasingly important in recent years.

Looking for alternatives

Decisive for the sound propagation is the sound insulation of existing components. While ceilings and walls were previously available as a carrier for sound-absorbing measures, the market is now focusing more and more on the floor.

This results from two structural changes: On the one hand, the trend towards a cool architecture, i.e. the large-scale use of materials such as exposed concrete or glass, the use of sound-reflecting materials in ceilings and walls – which consequently only leaves the floor as absorption area for reducing the reverberation time in such buildings.

On the other hand, in the course of more and more concrete core activation – especially within office buildings – walls and ceilings in the building are used to store thermal energy for heating and cooling purposes.

Due to the omission or limited availability of those components in which measures for sound insulation were previously integrated, as well as the reduced use of sound-absorbing suspended ceilings, the sound absorption must also be carried out in the floor.

The desire to be able to ensure optimal room acoustics in spite of trend-related structural changes was also addressed by the Weiss Raised Floor Systems.

Specializing in the fields of raised and hollow floor systems, the company has focused on the development of tailor-made and innovative solutions for specific customer and / or market requirements several times over the course of its history – and now presents a comprehensive range of raised floor systems made of different materials over special floors up to active panels.

In the case of the acoustic panel, the company works closely with an accredited test laboratory, which calculated, in over 60 examinations, the most favorable version of a room acoustics situation. In the following, we will first discuss these analyses in more detail; the terms used for the sound absorption levels are:

  • αw,B Sound absorption coefficient of the raised floor without carpet,
  • αw,T sound absorption coefficient of the carpet
  • res, αw resulting sound absorption coefficient of the raised floor with carpet.

At first, the examiners concentrated on the floor structures and considered a perforated calcium sulfate panel and a perforated steel ventilation panel. The sound-absorbing material used was generally mineral fiber material or melamine foam.

Lärmbekämpfung Bd. 14 (2019) Nr. 5 - September

At first, the examiners concentrated on the floor structures and considered a perforated calcium sulfate panel and a perforated steel ventilation panel. The sound-absorbing material used was generally mineral fiber material or melamine foam.

The measurements showed that steel as a building material is preferable to gypsum [figure 2 and 3]:

Another advantage of the steel lies in the capacity of the sound dissipation through the possible free area. Raised floor panels made of calcium sulfate can tolerate a maximum of 9% free area without being significantly impaired in their load capacity.

With a steel ventilation panel, a much higher performance can be achieved, since a free area of ​​up to 51% can easily be realized.

Due to the fact that this results in a larger absorber surface on a smaller area, significantly fewer steel panels achieve the same result compared to calcium sulfate panels – the ostensibly higher costs are thus amortized.

The effects of the perforation ratio on the different panels can also be seen in the graphics shown.

Schallabsorptionsgrade von gelochten Calciumsulfatplatten mit 50 mm

Figure 2: Sound absorption of perforated calcium sulfate panels with 50 mm thick melamine foam application at the back depending on the perforation ratio:

A – 30 mm thick calcium sulfate panel, perforation 4%, αw,B = 0.05 (L)
B – 40 mm thick calcium sulfate panel, perforation 15.2%, αw,B = 0.35 (L)

Schallabsorptionsgrade einer Stahllüftungsplatte mit Mineralfaserplatten-Hinterlegung

Figure 3: Sound absorption levels of a steel ventilation panel with mineral fiber plate attached to the back dependent on the perforation ratio:

A – Steel ventilation panel, perforation 16.9%, αw,B = 0.65 (MH)
B – steel ventilation panel, perforation 28.2%, αw,B = 0.75
C – steel ventilation panel, perforation 38.5%, αw,B = 0.70 (M)

Increasing sound absorption levels

In the next step the question of the covering was tackled.

Therefore, various carpets in rolls and tiles were examined, which differed, among other things, in terms of perforation.

Even though the best result in terms of sound insulation is achieved with panels without covering or identically perforated covering, this is neither usual nor visually appealing in an office space.

In order to avoid a perforated floor appearance, it is therefore most practicable to work with textile coverings such as carpet – an optimal result can be achieved in this case with self-laying carpet tiles including a perforated bottom.

The products specially developed for these applications were tested and measured in the following series of measurements.

These measurements showed that the carpet must have a sufficiently low flow resistance in order to obtain the highest possible sound absorption levels of the overall structure.

Wird die falsche Kombination aus Teppichböden und Doppelboden

Figure 4a: Choosing the wrong combination of carpet and raised floor, the sound absorption level of the raised floor is decreased by the carpet:

A – carpet, αw, T= 0,15 (H) (curve A, picture 4)
B – raised floor, αw, B= 0,65 (MH) (curve A, picture 3)
C – raised floor and carpet, res, αw= 0.75

Auf die richtige Kombination von Teppichboden und Doppelboden kommt es an

Figure 4b: It depends on the right combination of carpet and raised floor, resulting in sound absorption levels of:

A – carpet, αw,T= 0,20 (H) (curve C, picture 4)

B – raised floor, αw,B= 0,65 (MH) (curve A, picture 3)

C – raised floor and carpet, res, αw= 0.65 (M)

Carpets without perforation, i.e. with relatively high flow resistance, achieve in combination with the absorbent raised floor only a low resulting sound absorption.

Using standard carpets / carpet tiles, hence a wrong combination between carpet and raised floor, therefore results in a loss of dissipation [figures 4a and 4b]:

Another important aspect that should be mentioned here is that the perforated carpet is suitable for displacement ventilation of the room. Through a combination of perforated panels with absorber and without absorber, a ventilation concept can be implemented, which goes along with room acoustics.

Based on the results

As shown in the above measurements regarding the different degrees of absorption of the panel elements, the right combination of perforated textile covering, the size of the perforation ratio of the steel ventilation panel and the absorber built-in underneath are crucial for optimum acoustics.

Furthermore, the higher the assessed sound absorption levels of carpet and raised floor per se, the higher the resulting evaluated sound absorption coefficient.

Based on these calculations, Weiss Raised Floor Systems chose to combine the best components together for their acoustic raised floor panel to achieve excellent results in terms of room acoustics:

By means of an ideal combination of all necessary elements, this panel achieves outstanding values ​​regarding its absorption capacity within the measurements carried out.

Aufbau eines Akustikbodens

Figure 5 Structure of an acoustic panel

Looking more closely at the acoustic panel, it is composed of a self-laying, perforated textile covering and a perforated steel ventilation panel with integrated mineral wool absorber.

On the bottom, there is a galvanized steel sheet of 1.0 mm and height-adjustable M16 pedestals, also made of galvanized steel [figure 5].

Useful in many ways

Usable in all kinds of rooms such as offices, meeting rooms, auditoriums, training and research rooms, commercial / administrative buildings et cetera the acoustic panel offers – in addition to the now available walls and ceilings – many advantages:

For example, installations in the cavity are not affected, this can therefore continue to be used for wiring, piping, etc. The standard construction height is between 30 and 620 mm (clear height). Also, the ventilation through the cavity is not limited.

Another advantage is the uncomplicated replacement – any conventional panel element (600 x 600 mm) can be installed, which in turn means not only cost savings, but equally a compliance with required fire protection requirements, for example for escape routes.

With a point load of 3 kN and a building material class 1 according to EN 13501 all mechanical and static properties are retained.

Due to the broad portfolio of a large number of models with different absorption properties and the access to calculations and know-how of the market leader for acoustic raised floor, the Swiss company AGB Bautechnik, Weiss Raised Floor Systems is able to respond specifically to market requirements.

On request, customers can also purchase a smaller number of panels in order to realize a combination with conventional raised floor panels in the building.

QUELLE: © VDI Fachmedien GmbH & Co. KG, Düsseldorf 2019