Noisy open space: a comprehensive strategy for improving office acoustics

Acoustic environment optimisation must be based on objective, measurable parameters. An initial acoustic audit is the first strategic step in identifying precise sources of noise and determining which solutions (absorption, insulation or masking) will be most effective.

Professional acoustic measurements and analyses should be performed by accredited laboratories with expertise in standard and specialist measurements. The scope of measurements includes:

• equivalent noise level (Leq): verification of compliance with the 55 dB standard;
• reverberation time (RT60): a key parameter for assessing the need for sound-absorbing materials;
• sound insulation of partitions: assessment of whether partitions between rooms (e.g. conference rooms) are sufficient to block airborne sound transmission;
• noise from installations: measurement of noise generated by internal equipment (HVAC, server rooms).

The costs of the initial audit and design represent a small part of the total expenditure, but are critical to the success of the project. The cost of the measurements alone ranges from PLN 3,500 to PLN 6,500 net, while a comprehensive acoustic design including detailed recommendations and simulations starts at PLN 15,000 to PLN 20,000 net.

Reverberation time (RT60) is a basic metric for assessing the acoustic quality of a room. It is the time it takes for the sound energy in a room to decrease by 60 dB after the sound source has ceased. In rooms with hard surfaces and large volumes, sound waves bounce off walls, floors and ceilings, accumulating and creating reverberation.

Long reverberation times lead to excessive echo, which results in poor speech intelligibility. In such conditions, quieter but crucial details (consonants) are masked by louder, longer-lasting sounds (vowels). A short RT60 time is essential for clearer and more intelligible sound. For offices and conference rooms, the target RT60 value should be 0.4 - 0.6 seconds. This value can be estimated at an early stage of design using Sabine's formula, which takes into account the volume of the room and the absorption coefficients of all surfaces.

Sound absorption can be determined using the Noise Reduction Coefficient (NRC) or the sound absorption coefficient αw\alpha_wαw​.

Both indicators describe how effectively a given material absorbs sound energy instead of reflecting it.

The higher the NRC value (closer to 1.0), the better the material reduces reverberation and improves room acoustics.

For example, soft wall panels made of open-cell polyurethane foam can achieve an αw=0.80\alpha_w = 0.80αw​=0.80 value, which indicates their high effectiveness in sound absorption.

For open spaces, however, it is crucial to understand the duality of acoustic objectives. On the one hand, it is necessary to achieve a low RT60 through the extensive use of absorbent materials. On the other hand, in a quiet environment, reducing background noise can paradoxically increase speech intelligibility (Speech Transmission Index, STI) over longer distances, which compromises the privacy of conversations. For this reason, optimal acoustic design for open spaces requires a combination of passive materials for reverberation control and active systems (sound masking) for STI control and speech privacy.

The table below summarises the key technical metrics required in an office environment:

Noise reduction is most effective when intervention occurs at the earliest possible stage of a project. Guidelines indicate that the main issues concerning the creation of a high-quality acoustic environment must be taken into account as early as the Conceptual Design (Level 1). Early risk assessment allows designers to implement the appropriate partition structure and select building materials, which prevents the need for costly adaptation and retrofitting work in later phases.

In open-plan offices, the best organisational solution for noise control is to implement the concept of Activity-Based Working (ABW). ABW involves flexible space management, giving employees the freedom to choose a workspace suited to a specific task, which directly minimises acoustic disturbances.

The implementation of ABW requires the creation of specialised zones with different acoustic requirements:

Quiet zones/focus rooms: These are designed for individual work and tasks requiring the highest level of concentration. They must have the lowest RT60 values and the highest sound insulation to ensure complete protection from outside noise.

Acoustic booths and cabins: Solutions such as hushMeet.L ensure privacy and isolate the sounds of telephone conversations or short meetings. They are key to isolating the most distracting source of sound — the human voice — from the main workspace.

Team space/communication zones: These areas are designed for collaboration and brainstorming. The acoustics should support communication, but at the same time, these zones must be buffered and equipped with strong absorbers so that sound does not carry into quiet zones.

Relaxation zones: Places where employees can recharge and take a break from ‘virtual (and physical) noise’.

Passive solutions form the foundation of any successful acoustic strategy, focusing on controlling reverberation and blocking direct sound transmission.

The ceiling is the largest surface in a typical office space and plays a dominant role in controlling RT60. Hard ceilings reflect sound waves, increasing reverberation, which increases the overall noise level.

Suspended ceilings: The use of ceilings with high absorption properties, made of materials such as mineral wool or special metals (e.g. Armstrong ceilings), can significantly reduce noise levels by reducing reverberation. When selecting ceiling tiles, always verify their acoustic parameters, in particular the NRC coefficient. Reverberation reduction is critical, especially in conference rooms.

Free-hanging absorbers: Suspended acoustic curtains, ceiling panels (e.g. Selva Sky) or ceiling baffles are extremely effective at absorbing sound, as they often have two active absorption surfaces. Their advantage is that they do not require any interference with the floor or wall layout.

Sound absorption should be distributed across different planes to maximise control over sound waves.

Wall panels: Upholstered or foam wall panels (e.g. Silent Block, Fluffo Soft) absorb part of the sound wave. Their use is essential where hard, reflective surfaces predominate. Irregularly shaped panels also act as diffusers, scattering the remaining sound energy. These panels can also act as sound insulators if they are thick enough and cover the entire wall, helping to block the transmission of conversations from neighbouring rooms.

Desk-mounted and freestanding acoustic screens: Soft, upholstered panels attached directly to desks (e.g. Selva Desk) are designed to isolate a single workstation. They are most effective when placed close to the sound source, making them ideal for isolating the voice of an employee talking on the telephone. In high-intensity conversation environments, such as call centres, it is recommended to use tall, free-standing screens that surround the employee on three sides to provide complete protection from excessive noise.

Particular attention should be paid to the technical transparency of suppliers.

Although many manufacturers claim that their solutions are ‘highly effective in reducing noise’, the actual value of the investment depends on verified technical data.

Before purchasing, it is worth verifying certificates specifying sound absorption parameters, such as NRC or αw\alpha_wαw​.

The lack of this information may result in the selection of products with low acoustic efficiency.

Professional technical specifications should always be based on documented parameters (e.g. αw=0.80\alpha_w = 0.80αw​=0.80) rather than general marketing slogans.

The floor, although often overlooked, is an important element of absorption. Sound-absorbing floor coverings play a key role in reducing impact noise, minimising the sound of footsteps or furniture being moved, which is essential for controlling the transmission of impact sound. In addition, green walls are a modern solution which, apart from their aesthetic function and improvement of air quality, naturally dampen noise, acting as a sound-absorbing element.

After implementing passive solutions to reduce RT60, a key step in creating a noise-free environment is to implement active systems that protect speech privacy and prevent distraction.

Sound masking is an advanced technology based on psychoacoustics. The system involves emitting specially created, discreet background sounds at low volume levels. This sound, often described as similar to the hum of airflow, is precisely tuned to the frequency spectrum of human speech.

The purpose of sound masking is not to physically muffle speech. Instead, the system raises the level of background noise, which exploits a perceptual phenomenon. The added background noise makes speech heard from a distance less intelligible and, as a result, less distracting to those around.

Sound masking systems differ in their installation methods:

• direct-Field systems: Systems such as QtPRO install small loudspeakers (emitters) directly into the suspended ceiling plane, directing sound downwards. This is the industry's first technology to deliver excellent uniformity and energy efficiency;
• plenum systems (indirect/concealed): Speakers are mounted in the plenum space (the void above the suspended ceiling panels). The sound is diffused and returns to the room through the panels. Although these systems are more visually discreet, they often require precise tuning to ensure uniformity. The DynasoundPRO system is an example of a solution that allows remote, individual control of each loudspeaker.

The key difference is function: acoustic panels passively control sound behaviour in a room (reducing echo and RT60), while sound masking actively changes the acoustic environment by adding a controlled element. Passive (absorption) solutions address the issue of reverberation, while active (masking) solutions address the issue of speech intelligibility and privacy. An optimal office environment typically requires a synergy of both technologies.

Investment in acoustics must be considered from the perspective of a long-term cost-benefit analysis, where the return on investment (ROI) is calculated mainly on the basis of recovered productivity and improved employee health.

The investment should begin with professional consultation and an acoustic audit. As stated, achieving acoustic comfort through proper design costs less than subsequent, mandatory correction of acoustic defects. The initial cost of an acoustic design (from PLN 15,000) is strategically justified as insurance against costly redesign or losses resulting from inefficient operation.

The costs of individual technologies vary in nature, which determines the implementation phasing strategy:

• passive solutions (panels, ceilings): These are characterised by a lower cost per room and are easier to scale over time. They can be phased, starting with the areas with the highest acoustic priority. For example, wall panels can cost from PLN 25.94 to PLN 1,021.06 per unit;
• active solutions (sound masking): These require a higher upfront cost because the installation is centralised and must provide even coverage over a large open area. However, for large open spaces, sound masking is the most effective and cost-effective solution in the long term.

The return on investment in acoustic improvements is easy to quantify at the operational and health levels:

Health ROI: Noise reduction translates into reduced exposure of employees to chronic ailments and stress, which lowers absenteeism rates and medical costs. A healthy employee is more productive and satisfied.

Productivity ROI: The main return comes from recovering time lost to distractions. Recovering even a fraction of the 86 minutes lost per employee per day quickly covers the cost of investing in acoustic systems.

To maximise budget efficiency, the investment must be sequential. Proper implementation first requires the use of large-scale passive absorption materials (ceilings, panels) to achieve the target low reverberation time (RT60 \( 0.4-0.6 \) s). Then, on this prepared acoustic foundation, an active sound masking system should be implemented to optimise STI. The effectiveness of sound masking is directly dependent on low reverberation in the room; without sufficient absorption, the masking noise can become another irritating source of noise.

To transform an open-plan office into a space conducive to concentration and comfortable working, a comprehensive approach is required, based on three complementary pillars:

1. Absorb 
Reduce reverberation and echo.
Use materials with a high sound absorption coefficient NRC ≥ 0.80 on ceilings and walls to achieve a reverberation time RT60 in the range of 0.4-0.6 s.
Effect: less reflected noise and clearer speech.

2. Block
Separate loud sounds from quiet ones.
Introduce activity-based working (ABW) zones, acoustic booths and desk screens.
Effect: privacy for conversations and less sound transmission between workstations.

3. Cover
Control what cannot be silenced.
Use a sound masking system that reduces speech intelligibility (STI) and minimises distraction.
Effect: consistent, quiet acoustic background conducive to concentration.

The following steps will help the Facility Manager or Operations Director to effectively plan and implement acoustic optimisation:

1. Initial audit - Commission noise measurements (Leq, RT60, STI) from an accredited laboratory to assess compliance with the PN-N-01307:1994 standard.
2. Acoustic design - Take acoustic requirements into account at the office design stage to avoid costly alterations.
3. Zoning and working rules (ABW) - Designate zones for quiet, meetings and communication. Establish clear rules for the use of each zone.
4. Passive investments - Cover the main surfaces (ceilings, walls) with materials with NRC/αw ≥ 0.80 to reduce reverberation and reflected noise.
5. Technical insulation - Soundproof installation noise sources such as HVAC and server rooms.
6. Active investments - Install a sound masking system (Direct-Field or Plenum) in open areas to improve acoustic comfort.
7. Impact assessment (ROI) - Regularly monitor productivity, absenteeism and employee satisfaction indicators to assess the return on investment and confirm the improvement in efficiency.