How to use Metal in Acoustic Solutions | DAMPA

DAMPA® is a Danish company specialised in the development and production of acoustic steel and aluminium ceilings, as well as acoustic wall panels for the building industry, with sales exclusively in the European market.

Hard surfaces create a long reverberation time and unpleasant acoustics. But how can metal, which has a reflective surface, be the main element in DAMPA's acoustic solutions? The answer to this question is (almost) simple.

Perforations are crucial for the acoustic effectiveness of DAMPA’s acoustic solutions, and they create two types of absorbers: porous and resonance absorbers. DAMPA® offers over 30 different perforation designs, but the options vary depending on the material and product type. Larger perforations do not necessarily improve acoustic ratings.

By making a perforation in the metal, DAMPA can activate all three acoustic absorbents. A Porous absorbent consists of fibers, which start to move when hit by sound waves, and this way stops the sound. For example, clothes, carpets, curtains, etc.

A membrane absorbent is created in the space between two slabs. The air in the space works as a spring, which neutralizes the sound waves. The resonance absorbent is created in the perforation, where “air-plugs” make vibrations when hit by sound and calm down the sound waves. When combining all three absorbers, DAMPA® can create an acoustic solution, which is perfectly matched to the use of the room and needs of the users.

DAMPA recommends avoiding perforations larger than 10 mm in diameter as they lose their acoustic effectiveness. Perforations work well with diffuse ventilation systems, preventing drafts and ensuring even air distribution. Combining perforated metal panels with diffuse ventilation and DAMPA® Climate Ceiling provides a solution that addresses acoustics, ventilation, and temperature effectively.

Acoustic absorbents

By making perforations in the metal’s robust surface, DAMPA® products activate all three absorbent types: porous, membrane, and resonance absorbent. Since 1951, DAMPA has created acoustic solutions of high quality by combining all three absorbent types.

To better understand how DAMPA metal ceilings and wall panels can be acoustically, users will have a look at the different absorbent types.

Porous absorbent A porous absorbent consists of fibers, which start to move when they are hit by sound waves. The sound waves will, in this process, be stopped and converted to heat through the moving fibers. An example of places that are filled with porous absorbents are clothing shops. Where one would experience different sounds and acoustics in other shops, the clothes (or porous absorbents) will lower the reverberation time significantly and make the shop a pleasant place to shop and stay. The porous absorbent is effective in high-frequency areas such as whistles, computer devices, screaming, glass breaking, or nails on a chalkboard, but not the lower.

Membrane absorbent A membrane absorbent is created in the space between two slabs. An example is the membrane absorbent created in the space between the unperforated area of the wall panels and the wall. The air in the underlying space works as a spring and together with the DAMPA metal sheet, it constitutes a swinging system, which constantly searches to neutralize the sound waves. This absorbent is a contrast to the porous absorbent and is most effective in low-frequency areas, sounds such as severe weather, sound waves that often sound “lower’ to the human ear, “rumbly” sounds that you feel as much as you hear.

Resonance absorbent The last absorbent type is the resonance absorbent, which is a development of the above-mentioned membrane absorbent. The resonance absorbent is also using the hard surface, however, this time it is the perforation and its edge which is the main elements. In these holes, you will find “air plugs”, which, when they are hit by sound waves, will make vibrations, which will be affected by the air or porous materials in the underlying space. The air or the porous material will work as a spring, which seeks to calm down the vibrating “air plugs”. This vibrating system is created by the energy of the sound waves, and therefore, the sound is no longer reflected in the room. Just as the membrane is absorbent, this absorbent is most effective in the lower frequencies.

In DAMPA's acoustic metal solutions, we achieve the best acoustic experience by using a perforated metal surface combined with a porous absorbent, e.g., DAMPA's acoustic felt. When combining these three different absorbent types, DAMPA® can create an acoustic solution customized to the use of the room and the user’s needs.

Robust acoustic solutions

It is not only because of the acoustics that metal is an ideal building material. By exploiting the metal’s robust qualities, it is possible, even in the bustling areas, to achieve long-lasting solutions – this is both an advantage for the planet and the operating budget.

At the same time, it is a hygienic material, which makes DAMPA's acoustic solutions to walls and ceilings ideal for hospitals, children’s institutions, schools, restaurants, and many more places, as it can easily be cleaned and wiped off. Furthermore, the metal surface gives you total freedom to design the surface as you wish, whether it is colorful or with digital print.

Metal and sustainability

Metal and sustainability do not often appear in the same sentence. When metal is produced from new, it is a heavy material to extract, it uses a lot of energy, and produces a lot of waste. However, when the metal is produced, it can, with relatively few resources, be recycled 100 % without leaving the circular orbit. DAMPA® respects the materials and is always securing the right waste sorting at source, so DAMPA can ensure that the material does not cease to exist.

How can metal be acoustically effective?

This is where the perforations come into play and play a crucial role. When DAMPA creates an acoustic element for the ceiling or the wall, the thin metal panel becomes the membrane absorber.

By perforating the robust surface of the metal, we add two additional absorbers: the porous absorber and the resonance absorber. The porous absorber comes in the form of DAMPA's acoustic felt, accessible through the perforations.

As for the resonance absorber, this is where the perforation shines. Within each perforation are small “air plugs” that vibrate against the acoustic felt and the cavity behind it.

By combining the hard surface with the perforations and the underlying acoustic felt, we activate all three types of absorbers – thereby integrating the best of acoustic principles into all DAMPA's acoustic solutions and ensuring optimal acoustic performance.

Considerations when choosing perforations:

DAMPA® offers over 30 different perforation designs. However, the choices available depend on the product type you intend to use in the design. For example, the cassettes typically have a larger surface area where DAMPA can perforate compared to the lamellas. Therefore, DAMPA can experiment with various sizes and shapes of perforations with the cassettes.

Additionally, we need to consider the material. The size of the perforation affects the strength of the material. A larger perforation weakens the material, so it’s necessary to increase the thickness to maintain durability and aesthetic appeal.

Large perforations do not enhance acoustic performance, while a common misconception is that larger perforations lead to better acoustic ratings. However, when perforations are too large, they affect the resonance and membrane absorption, resulting only in what we call acoustic transformation, where the metal loses its impact on acoustic performance.

DAMPA® does not recommend perforations larger than 10 mm in diameter, as beyond this size, they become more decorative than functional for acoustics.

Perforations are crucial for a good indoor climate, as they have a positive impact on acoustic performance. They also contribute positively to temperature and ventilation. The perforations are particularly effective in diffuse ventilation scenarios.

Diffuse ventilation involves creating positive pressure above the ceiling, pushing fresh air down through the ceiling. The perforations spread across the panel, help distribute air evenly, preventing drafts and ensuring effective ventilation.

Looking at DAMPA® Climate Ceiling, perforations play a minor role in radiant heating and maintaining optimal temperature. Here, the metal panel itself plays a crucial role due to its rapid response to temperature changes.

By combining the perforated metal ceilings with diffuse ventilation and DAMPA® Climate Ceiling, we create a ceiling surface that addresses acoustics, ventilation, and temperature without compromising on design, functionality, or indoor comfort.