Optimizing room acoustics – How to ensure successful collaboration between architects and building owners

High noise levels can not only impair well-being but also cause serious health problems such as heart disease, tinnitus, and sleep deprivation. Therefore, optimizing room acoustics is a crucial factor when planning buildings; however, this aspect is often underestimated.

The varying acoustic requirements of different room uses make early collaboration between architects and building owners . The expertise of room acousticians is also crucial for achieving optimal acoustic design. Building acoustics is tasked with thoroughly examining the sound conditions in residential and commercial buildings and planning the building structures in such a way as to optimize these conditions.

Contrary to popular belief, room acoustics encompasses far more than simply optimizing reverberation times. Through strategic spatial planning, architects can specifically influence how sound is reflected, absorbed, and diffused. Professional acousticians are an invaluable asset when it comes to saving time and achieving a satisfactory result.

Why room acoustics need to be planned early on

Acoustic problems can be found in almost all untreated rooms, whether in new or old buildings. To ensure the long-term success of a construction project, it is crucial to plan room acoustics early in the process.

Acoustics as part of spatial perception

Our perception of sound in a room is strongly influenced by its acoustics. With approximately 25,000 sensory hair cells, our ears can process about 50 impressions per second, twice as much as the eye. They are also capable of finely distinguishing around 400,000 different tones. Despite the superior capabilities of our ears compared to our eyes, architecture continues to place more emphasis on the visual than on the auditory.

The geometry of a room and reflective surfaces such as exposed concrete or glass determine its reverberation. This form of perception, also known as audibility, directly influences how we experience and use a space.

Consequences of poor acoustics for users and building owners

Research shows that even low but persistent noise levels can cause headaches, fatigue, concentration problems, stress, anxiety, and in the worst case, depression. In extreme cases, hearing damage can even occur.

In offices, noise is a significant disruptive factor that reduces performance and increases the error rate in knowledge-intensive work.

Poor speech intelligibility is the reason why people have to speak louder; this increases the overall noise level and leads to a negative spiral.

In schools, noise levels often exceed 85 dB(A) – a level at which hearing protection should actually be worn. In restaurants, poor acoustics are often the reason why guests leave the establishment prematurely.

Why subsequent optimization of acoustics is not advisable

Structural measures to reduce reverberation time are often costly and tricky to implement if planned retroactively. Therefore, professional acoustic optimization should be planned from the outset.

This is particularly important due to the following circumstance: Modern architecture often relies on sound-reflective materials such as glass and concrete, which cause high sound reflections and reverberation times.

The advantages of early acoustic planning are therefore almost self-evident: it prevents unwanted costs due to rework, allows acoustics to be integrated into the design concept, and improves the efficient use of spaces. Early communication between architects, clients, and acousticians is advisable in order to jointly define the acoustic requirements during the planning process.

Task allocation: Who takes on which role in the planning process?

Successful room acoustics planning is the result of collaboration between various stakeholders. A clear division of tasks and responsibilities is the foundation for optimal results.

The architect's tasks with regard to acoustics

Architects make fundamental decisions regarding room geometry, dimensions, and materials that directly impact acoustic quality. Even in the planning phase , it is desirable for architects to consider challenges such as the excessive use of glass or the creation of open, multifunctional spaces.

However, it is not necessary for the basic architectural form to be perfect at this stage. With appropriate secondary measures, almost any primary structure can be made acoustically functional.

When to consult a room acoustician

Often, a building physics engineer consulted to address aspects of sound insulation and room acoustics. It is advisable to involve these specialists in the early planning stages. This is particularly crucial for complex construction projects such as auditoriums or concert halls, as many different requirements must be met.

Exchange between architect and acoustician

Communication and dialogue are crucial for jointly defining acoustic requirements during the planning process. Past experience has shown that the combination of expertise, experience, and continuous communication yields the best results.

Owner's responsibility in acoustic decisions

The client bears primary responsibility in the acoustic planning process. Even in the planning phase, they must assess the noise impact and define specific requirements in the project specifications. They should also contact the relevant authorities early on if harmful environmental impacts cannot be ruled out.

Technical foundations for successful collaboration

Successful collaboration between architects and clients requires a shared understanding of the technical principles of room acoustics. This knowledge enables well-informed decisions and avoids costly corrections after completion of the work.

Basic concepts: reverberation time, sound propagation, frequency

The key parameter in room acoustics is reverberation time ; it is measured in seconds. It indicates how long it takes for the sound pressure level in a room to decrease by 60 dB. Originally developed by the American physicist Wallace Clement Sabine , it is calculated using the formula T = 0.163 × V/A , where V represents the room volume in m³ and A represents the equivalent sound absorption area in m².

Sound initially propagates as direct sound , followed by early reflections from the walls, which are in turn reflected and dampened. It is surprising that sound travels faster in denser materials than in air.

The frequencies determine the pitch – low frequencies produce low tones, while high frequencies produce high tones. The effectiveness of acoustic measures varies greatly with frequency.

Materials and their acoustic properties

In materials science, a distinction is made between:

• Porous absorbers such as carpets , insulation materials or curtains: They particularly reduce medium and high frequency sound.
• Resonance absorbers such as plasterboard: They vibrate and thus absorb low-frequency sound.
• Helmholtz resonators : They utilize the excitation of air masses through slits or holes.

The sound absorption coefficient α shows how well a material absorbs sound; it can take values ​​between 0 (complete reflection) and 1 (complete absorption).

Understanding noise and acoustic defects in the room

To understand the problems with acoustics, it is necessary to distinguish between two main categories of noise and defects:

1. Airborne sound : Propagates through pressure waves in the air. Indoors, it manifests primarily as reverberation or excessive reverberation time.
2. Structure-borne sound : This is transmitted directly through solid building elements in the form of vibrations. It involves the transfer of energy from one point in the structure to another, where it manifests itself again as sound in the air.

RUHIG sound insulation provides a direct comparison between good and bad room acoustics using an office as an example in the following video:

Simulations and 3D planning as a common basis

Before construction begins, 3D acoustic simulation to determine how sound will propagate. A thorough 3D model of the room should be the starting point. There are many different ways to do this, including statistical models, ray tracing, and even complex finite element methods.

Avoid typical mistakes when choosing materials

A common problem is that different frequency bands are not absorbed uniformly. If the reverberation time is not consistent across all frequency bands, the acoustics can deteriorate. Furthermore, placing absorbers in the wrong location can lead to less than ideal results.

For example, absorbers should not be placed on the ceiling or behind the loudspeaker in lecture halls.

Creating ideal room acoustics should be done strategically

Ideal  room acoustics  are achieved through a combination of two complementary principles: sound absorption and sound insulation.

• Sound absorption  focuses on reducing sound energy inside the room, shortening the reverberation time and minimizing reverberation.
• Sound insulation  aims to prevent the transmission of sound from one room to another through suitable building constructions.

Effective sound insulation of a wall  is achieved by increasing its surface mass and using multi-layered constructions. Critical points for sound transmission are openings and joints in walls, such as doors, windows, electrical outlets, or pipe penetrations. To increase their effectiveness, it is necessary to use acoustic versions with higher sound insulation ratings, special acoustic doors and seals, and to insulate all pipe and cable penetrations.

Implementing these principles makes it possible to transform problematic spaces into acoustically pleasant environments. Investing in a suitable acoustic solution therefore affects not only comfort, but also the functionality of the space and the quality of life of its users. So choose wisely.

Best practices from real-world experience

The best evidence for the successful implementation of acoustic concepts is concrete examples. They show how theory can be successfully put into practice.

Example 1: Multifunctional conference room

Modern conference centers should accommodate all possible event formats. An electroacoustic system that creates different room acoustics at the touch of a button has been installed in the VILCO congress center in Bad Vilbel.

An impressive effect: MAKUSTIK fine micro-panels with 467,000 holes per square meter enable exceptionally high sound absorption. The "Voice Lift" system allows speakers to perform without a microphone, while electronic reverberation can be added for musical performances.

Example 2: School building with soundproofed zones

The Elbe School for children with hearing impairments is an excellent example of accessible room acoustics. New school concepts bring particular challenges: Open learning environments require new solutions for acoustic design. In 2023, the Montag Foundation for Youth and Society published a 120-page guide offering concrete suggestions for clusters and open learning spaces.

Example 3: House with home cinema

Home theaters require a balanced relationship between living environment and optimal acoustics . Corner absorbers are an effective solution for combating frequencies below 100 Hz. Acoustic panels , which also serve as decorative elements, are ideal for first reflections. A high-pile carpet absorbs high frequencies while simultaneously creating a cozy cinema atmosphere.

What all successful projects have in common

The successful implementation of projects often depends on early acoustic planning. For example, in Dubai, acoustic panels made of Alpine hay with a reverberation time of αw = 0.85 according to DIN ISO EN 354 were integrated into the design concept of a project.

The Blaibach concert hall uses foamed glass gravel concrete, which has excellent insulation values ​​and surprisingly good acoustic properties.

Ultimately, collaboration between architects, acousticians and building owners is crucial to reconciling technical requirements with aesthetic demands.

Let's summarize

It should be noted that improving room acoustics is a complex process that requires the collaboration of various specialists. For optimal results, architects, building owners, and acoustics experts should engage in professional dialogue early on.

It is crucial to consider acoustic planning from the outset. Subsequent corrections are not only expensive but often difficult to implement.

The selection of materials and their strategic arrangement are of immense importance. Even if the reverberation time is calculated correctly, unbalanced absorption and different frequencies can lead to unsatisfactory results.

Different usage requirements necessitate individual solutions. The practical examples presented here have demonstrated this. While a conference center needs variable acoustic conditions, school buildings with open learning landscapes present different challenges.

Nevertheless, common success factors exist: planning in the early phase, collaboration across disciplines, and finding a balance between technical requirements and aesthetic demands.

In summary, successful room acoustics are far more than just pleasant listening; they protect the health of users, increase their well-being, and significantly improve the functional quality of spaces. The key to this is dialogue between all parties involved – the earlier it begins, the better the end result.