Article: Case studie: The Union - Engsøhus

Oct 10, 2022

Case studie: The Union - Engsøhus

Engsøhus is part of PFA's "The Union by PFA" concept, which offers attractive and flexible leases to companies that do not want to compromise on quality and interior design. The Union it is located at Mosevej 3. m.fl., 8240 Risskov

The property is shared by a large and beautiful arrival area as well as the house's large meeting center and delicious canteen with a large kitchen. The house was born on a basic principle of creating a larger and more flexible solution with focus on affordability. As a tenant in Engsøhus, you get access to more for less.

Good acoustics are not a luxury, but a prerequisite for well-being, focus, and productivity.

From open-plan offices to modern homes with concrete, glass, and steel, most contemporary spaces are designed with aesthetics in mind but without considering how sound behaves. The result is noise that lingers, speech that becomes unclear, and a soundscape that causes stress rather than comfort – as discussed in our feature on decorative soundproofing panel ideas.

At Arturel, we believe that the conversation about acoustics deserves a scientific foundation. That means going beyond surface-level claims and instead explaining the physics of how sound waves interact with materials, how energy is transformed when waves hit porous structures, and why different frequencies demand different approaches.

Diagram showing sound wave reflection, transmission, and absorption that explains how acoustic panels work.

How do acoustic panels work?

Acoustic panels work by turning sound energy into heat through microscopic friction inside the material.

When a sound wave travels through air, it behaves as a pressure fluctuation. Upon reaching a surface, three things can happen:

1. Reflection – Part of the wave bounces back into the room. This causes echoes and reverberation, which shape how long sound lingers in a space.

2. Transmission – Part of the wave passes through the material. This is the pathway for noise traveling between rooms or floors.

3. Absorption – Part of the wave enters the material and loses energy. In porous or fibrous structures, this energy is converted into heat through microscopic friction, reducing the overall sound level.

Absorption occurs when the pressure wave enters a porous or fibrous structure. As air particles are forced through the small gaps between fibers, their kinetic energy is transformed into heat by viscous friction. A process too small to be felt as warmth, but powerful enough to reduce the strength of the sound.

The efficiency of absorption depends strongly on the relationship between frequency and material thickness. Low-frequency sound waves have long wavelengths and require thicker or denser structures to be effectively dampened, while high frequencies with short wavelengths can be absorbed by thinner materials. This is why an acoustic panel that performs well in the speech range of 500–2000 Hz might need additional thickness to tackle the rumble of ventilation systems or bass-heavy environments.

Research on natural fibre composites confirms this principle. Studies show that fibres such as kenaf, hemp, and wool have excellent porosity and tortuosity, making them effective at dissipating sound energy while remaining lightweight and sustainable. Their fibrous network structure mimics what engineers also achieve with advanced synthetic materials:

A labyrinth that forces sound waves to lose energy as they travel through.

At Arturel, we apply the same principles but combine them with circular design. Our Kvadrat series, for example, is made from upcycled textile waste – giving discarded wool a second life as a highly effective absorber. By engineering fibre density and thickness, we ensure that each panel not only performs acoustically but also tells a story of material innovation. The same tangled fibre structures that make textiles soft and flexible also make them highly efficient at reducing reverberation.

In essence, acoustic panels are not passive decorations. They are precisely engineered systems that balance material choice, thickness, and fibre architecture to shape how sound behaves in a room.

Graph showing how Arturel acoustic panels absorb sound at different frequencies compared to other brands.

What is NRC and why does it matter?

Noise Reduction Coefficient (NRC) is a single-number rating that describes how effectively a material absorbs sound, expressed on a scale from 0.0 to 1.0.

An NRC of 0.0 means no absorption (the panel reflects all sound), while an NRC of 1.0 means total absorption. In practice, most acoustic materials fall between 0.3 and 0.95, depending on their composition and thickness. This rating is especially useful for designers and architects because it condenses complex frequency data into a simple number that can guide material selection.

The NRC value is determined through standardized laboratory tests across the frequency range of 250–2000 Hz, as described in acoustic testing standards. This range covers the majority of human speech and everyday noise. The result is an average absorption coefficient across these bands. For example, if a panel is rated NRC 0.85, it means the surface absorbs around 85% of the incident sound energy within that range – dramatically reducing reverberation and improving clarity.

However, one limitation of NRC is that it provides only a single average, while real-world performance often varies across frequencies. Two materials can both have NRC 0.80 but behave very differently. One might absorb low frequencies poorly but excel at high frequencies, while another has a more balanced profile. That distinction can be critical when designing offices, restaurants, or performance spaces where different types of noise dominate.

Scientific research on sandwich and microperforated panel structures highlights how absorption performance can be fine-tuned across frequencies. These studies demonstrate that by adjusting cavity depth, perforation diameter, or layer composition, engineers can shift absorption peaks and create materials that target specific noise problems.

Our PET panels, for example, are available in both 9 mm and 24 mm thicknesses. While the thinner version provides reliable absorption in the mid- and high-frequency ranges typical of office noise, the thicker variant achieves stronger performance across the lower speech and HVAC frequency bands. For architects and designers, this means NRC is not just a number, but it is a decision tool that must be interpreted in relation to the soundscape of each project.

In short, NRC matters because it bridges laboratory science and real-world acoustics, providing a simple rating that hides a complex balance of physics, materials, and design choices.

Hands assembling multi-layer acoustic panels designed for sound absorption inside a room.

Sound absorption vs. soundproofing

Sound absorption improves the sound quality inside a room, while soundproofing blocks sound from entering or leaving it. Although the terms are often used interchangeably, they describe very different acoustic mechanisms and lead to very different design outcomes.

Absorption is about managing what happens to sound energy after it is generated in a room. Acoustic panels absorb a portion of the sound waves that strike them, preventing repeated reflections and reducing reverberation time. The result is a calmer, clearer acoustic environment where speech is easier to understand and background noise feels less fatiguing.

Soundproofing, on the other hand, addresses transmission by reventing sound from passing through walls, floors, or ceilings. This requires mass, airtight construction, and often multiple layers of dense materials. A lightweight wall with decorative acoustic panels may reduce echo inside the room, but it will not stop traffic noise or a loud neighbor from being heard. To achieve that, engineers rely on barrier design, heavy partitions, and resilient connections that break vibration paths.

Scientific research underlines this distinction. Studies on acoustic metamaterial sandwich panels show how advanced multi-layered systems can achieve high sound transmission loss by combining resonant elements with traditional mass-barrier approaches. These structures are optimized to block specific frequency ranges, demonstrating how soundproofing is an engineering problem of controlling vibration and transmission paths, not surface absorption.

For end-users, the key is setting the right expectations. Acoustic panels are not ‘miracle modules’ that make noise vanish – as we also explain in our article on do soundproofing panels work. Instead, they transform the experience of sound within a room by reducing harsh reflections, making speech more intelligible, and lowering the mental load of constant background noise. In many cases, panels form part of a larger strategy:

Absorption for comfort, soundproofing for isolation.

Our panels are designed for absorption, not soundproofing in its technical sense, and we emphasize the wellbeing benefits that come from better room acoustics.

Acoustic materials and advanced panel design

The design of acoustic materials determines how effectively panels can control sound, from simple porous fibers to advanced periodic structures and resonant metamaterials. Researchers have long investigated how different material architectures influence absorption and transmission loss, showing that the internal geometry can be just as important as the raw material itself.

Close-up of porous PET fiber structure used in Arturel acoustic panels to absorb and dissipate sound.

One approach is the use of periodic structures, where panels are engineered with repeating patterns that scatter and redirect sound waves. Inspired by natural systems, these designs can target specific frequency bands, creating highly efficient absorption or insulation at narrow ranges. Bioinspired periodic panels show how structural optimization can increase insulation without necessarily adding bulk, making them an attractive field of research for architectural acoustics. Similarly, sonic crystals – arrays of regularly spaced elements – can create “band gaps” where certain frequencies are blocked, a principle borrowed from physics and adapted to acoustics.

Another well-established method is the use of porous materials, which dissipate sound energy by converting it into heat through friction within microscopic pores. Studies confirm that porous absorbers and double-panel configurations are proven to balance absorption efficiency and weight, highlighting how such materials can dramatically improve insulation when combined with structural layers, balancing lightweight design with effective absorption. These findings connect laboratory experiments to real-world product development, showing that porosity remains one of the most practical solutions for broad-spectrum absorption.

In practice, however, not every innovation translates smoothly into commercial or architectural use. Metamaterials and resonant systems can offer impressive performance in controlled laboratory conditions, but they are often complex, costly to produce, and optimized for narrow frequency bands.

That is why at Arturel we rely on engineered porous PET panels, a material that combines sustainability with acoustic effectiveness. Made from recycled polyester, our panels take advantage of porosity at the fiber level to provide broad, reliable absorption without the need for highly specialized designs. Ensuring that advanced acoustic science is applied in a way that makes sense for everyday spaces.

Acoustics in practice by changing the soundscape

The way we experience sound in a room is less about absolute silence and more about clarity and balance. Acoustic treatment changes the soundscape by shaping reverberation time, frequency response, and speech intelligibility – not by eliminating sound.

Arturel acoustic panels installed in office space to reduce RT60 and balance speech frequencies for clarity.

A central parameter is RT60, the time it takes for sound to decay by 60 decibels after the source stops. In practical terms, RT60 determines whether a meeting room feels crisp and intelligible or muddy and exhausting. Shorter reverberation improves clarity for speech, while longer reverberation can enrich music but quickly becomes disruptive in workspaces. Architects and acoustic engineers often use RT60 as the baseline metric for evaluating room quality, since it reflects the cumulative effect of absorption, reflection, and diffusion.

Equally important is the frequency balance. Acoustic panels are not designed to remove all sound but to manage how different frequencies behave. For example, low frequencies tend to linger, while high frequencies are more easily absorbed. Effective treatment ensures that no part of the spectrum dominates, creating a balanced and comfortable environment. A snackable fact to keep in mind:

Around 50% of speech energy lies between 500 and 2000 Hz, which explains why mid-frequency absorption is so critical for intelligibility.

In real-world projects, mistakes often stem from oversimplifying acoustics. The first is using too few panels. One or two absorbers in a large office will barely shift RT60. Too few panels or poor placement often leads to ineffective results – something we outlined in our guide on 7 signs your home has bad acoustics.

The second is placing panels incorrectly. Positioning absorbers only on one wall or too high above conversation zones can leave critical reflections untouched. Optimal layouts consider both coverage and distribution, targeting reflection points where sound bounces directly between people.

Sustainable materials and design in Arturel acoustic panels

At Arturel, acoustic performance is inseparable from material choice, sustainability, and design. Our panels are engineered to combine scientific effectiveness with environmental responsibility – without compromise.

Acoustic art panels crafted from upcycled Danish Royal Guard uniforms, showcasing sustainable design.

The foundation is a porous PET felt, made from 75% ocean-bound plastic. From an acoustic perspective, the porosity of the fibers enables sound energy to dissipate as heat. By aligning material science with waste reduction. This dual benefit means every panel contributes to both a healthier soundscape and a healthier planet.

Alongside PET, Arturel collaborates with Kvadrat to upcycle textile waste into acoustic solutions. The heterogeneous fiber structures create micro-channels that enhance absorption across a broad frequency range. In practice, this means panels derived from post-consumer textiles achieve measurable improvements in mid- and high-frequency absorption – precisely where speech clarity is most needed.

Performance is validated with hard data and Arturel panels consistently achieve an NRC of 0.85, which corresponds to absorbing 85% of incident sound energy in the measured spectrum. This level of absorption ensures reliable performance across offices, meeting rooms, and open workspaces where control of reverberation time is critical.

Finally, acoustic performance and sustainability are matched by aesthetic versatility. Our designs – such as Wave, Arch, and Stone – are inspired by natural forms, allowing architects and clients to integrate acoustic treatment as a visible part of interior design rather than a hidden technical fix. These shapes create diffusion as well as absorption, offering both functional and visual impact.

Frequently asked questions about acoustic panels

How many acoustic panels do I need?

The number depends on room size, shape, and surface materials. As a rule of thumb, covering 20–30% of the wall surface in offices or classrooms brings reverberation time (RT60) down to a comfortable level. Large or highly reflective rooms may need more coverage, often on both walls and ceilings, to reach balanced acoustics.

How effective are soundproof panels?

Most products marketed as “soundproof panels” are actually sound absorbers. They reduce echo and reverberation inside the room but do not block external sounds such as traffic or neighbors. True soundproofing requires heavy, airtight constructions like multi-layer walls or floating floors, not lightweight decorative panels.

How to improve acoustics in a large room?

Large rooms need distributed absorption. This is achieved by combining wall panels, ceiling baffles, and sometimes freestanding dividers to cover different reflection paths. Positioning panels at first reflection points (e.g., opposite speakers or meeting tables) is critical to achieve clarity across the whole space.

How is sound absorption different than light absorption?

Sound absorption happens when pressure waves move through a porous structure and lose energy as frictional heat, typically inside fibers or foams. Light absorption, in contrast, occurs when electromagnetic radiation is converted to heat at the surface of a material. The processes are analogous but occur through very different physical mechanisms.