Optimizing Room Acoustics – How to achieve successful collaboration between Architects and Clients

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 designing buildings; however, this aspect is often underestimated.

The varying acoustic requirements for various room uses make it essential that architects and building owners collaborate early on . The expertise of room acousticians is also crucial for achieving optimal acoustic design. Building acoustics is responsible for examining sound conditions in residential and commercial buildings in detail and planning structural designs to optimize these conditions.

Contrary to popular belief, however, considering room acoustics encompasses far more than just optimizing reverberation times. Architects can specifically influence how sound is reflected, absorbed, and diffused through strategic spatial planning. Professional acousticians are a tremendous help when it comes to saving time and achieving satisfactory results.

Why room acoustics must be planned early

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

Acoustics as part of spatial perception

Our hearing perception 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 many as the eye. They are also capable of finely distinguishing approximately 400,000 different sounds. Despite the superior performance of our ears compared to our eyes, architecture continues to place more emphasis on the visual than the aural.

The room's geometry and reflective surfaces, such as exposed concrete or glass, determine a room's reverberation. This form of perception, also known as audibility, has a direct impact on how we experience and use a space.

Consequences of poor acoustics for users and building owners

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

In offices, noise is a significant nuisance that reduces performance and increases the frequency of errors 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 often cause guests to leave early.

Why subsequent optimization of acoustics does not make sense

Structural measures to reduce reverberation time are often costly and difficult to implement when planned retrospectively. 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-hard materials such as glass and concrete, which cause high sound reflections and reverberation times.

The benefits of early acoustic planning are therefore almost obvious: It prevents unwanted costs from subsequent improvements, allows acoustics to be incorporated into the design concept, and improves the efficient use of spaces. Early communication between architects, clients, and acousticians is beneficial in order to jointly define acoustic requirements during the planning process.

Allocation of tasks: Who takes on which role in the planning process?

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

Tasks of the architect with regard to acoustics

Architects make fundamental decisions about room geometry, dimensions, and materials that have a direct impact on acoustic quality. Even during the planning phase , it's 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 a room acoustician should be consulted

building physics engineer is often consulted to address aspects of sound insulation and room acoustics. It is advisable to involve these experts early in the planning phase. It is especially crucial to involve them early on in 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 early in the planning process. History has taught us that the combination of expertise, experience, and continuous communication delivers the best results.

Responsibility of the client for acoustic decisions

The primary responsibility in the acoustic planning process lies with the client. They must assess the noise impacts early in the planning phase and specify specific requirements in the 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 fundamentals of room acoustics. This knowledge enables informed decisions and avoids costly corrections after completion of the work.

Basic concepts: reverberation time, sound propagation, frequency

The key parameter of 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 first travels as direct sound , followed by early reflections from the walls, which in turn are reflected and dampened. It's amazing that sound travels faster in denser materials than in air.

Frequencies determine the pitch—low tones are heard at low frequencies, while high tones are heard at high frequencies. 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 resonate and thus absorb low-frequency sound.
• Helmholtz resonators : They use the excitation of air masses through slits or holes.

The sound absorption coefficient α indicates 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 of acoustics, it is necessary to distinguish between two main categories of noise and defects:

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

RUHIG Sound Insulation provides us with a direct comparison between good and bad room acoustics using the example of an office in the following video:

Simulations and 3D planning as a common basis

Before construction, 3D acoustic simulation to determine how sound will propagate. A thorough 3D model of the space 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 evenly. If the reverberation time isn't 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, in lecture halls, absorbers should not be mounted on the ceiling or behind the loudspeaker.

The creation of ideal room acoustics should be done strategically

The  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 a room, shortening reverberation time and minimizing reverberation.
• Sound insulation  aims to prevent the transmission of sound from one room to another through appropriate building construction.

Effective sound insulation of a wall  is achieved by increasing its surface mass and using multi-layer construction. 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, use special acoustic doors and seals, and 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 not only concerns comfort but also improves the functionality of the space and the quality of life of its users. So choose wisely.

Best practices from practice

The best evidence for the successful implementation of acoustic concepts is concrete examples. They demonstrate how theory can be successfully applied in 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 was installed at the VILCO Conference Center in Bad Vilbel.

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

Example 2: School building with soundproof zones

The Elbschule for children with hearing impairments is an excellent example of accessible room acoustics. New school concepts bring with them unique challenges: Open learning environments require new solutions for acoustic design. The Montag Foundation for Youth and Society published a 120-page guide in 2023 that offers concrete suggestions for clusters and open learning spaces.

Example 3: Residential building with home cinema

Home theaters require a balance between living space and optimal acoustics . Corner absorbers are an effective solution for combating frequencies below 100 Hz. Acoustic screens , which also serve as decorative elements, are ideal for early reflections. Deep-pile carpeting absorbs high frequencies while creating a cozy theater 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 incorporated into the design concept.

The Blaibach Concert Hall uses glass foam gravel concrete, which has excellent insulation values ​​and surprisingly good acoustic properties.

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

We summarize together

It's important to note that improving room acoustics is a complex process that requires the collaboration of various experts. For optimal results, architects, building owners, and acoustic experts should engage in professional dialogue early on.

It's crucial to consider acoustic planning from the outset. Making adjustments afterward is not only expensive but often difficult to implement.

The selection of materials and their strategic placement are of immense importance. Even if the reverberation time is mathematically correct, unbalanced absorption and varying frequencies can lead to unsatisfactory results.

Different usage requirements require individual solutions, as the practical examples presented here demonstrate. While a conference center requires variable acoustic conditions, school buildings with open learning environments 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 preserve the health of occupants, increase their well-being, and significantly improve the functional quality of spaces. The key to this is dialogue between all stakeholders – the earlier it begins, the better the end result.