Why Your New Office Sounds Terrible Even Though Nothing Failed a Test

Glass partitions, polished concrete and exposed ceilings pass insulation tests but wreck speech clarity. Why offices sound bad and how to fix them.

ACOUSTICS

8/9/20266 min read

The fit-out is complete. The glass partitions are installed, the polished concrete floor is finished, and the exposed-services ceiling delivers the desired industrial appearance.

The office photographs well. The sound-insulation testing, if required, has passed.

Yet the boardroom is exhausting to use. Video calls contain a noticeable wash of echo behind every voice. A meeting of six people sounds confused and crowded, while participants lean forward and repeatedly ask one another to repeat themselves.

Nothing necessarily failed. The problem may simply not have been included in the project’s acoustic performance requirements.

The issue may not be sound insulation. It may be reverberation.

Two different acoustic problems

Sound insulation measures how much sound travels from one space to another through a wall, floor, ceiling, door, or façade. It is concerned with separation between rooms.

Reverberation is different. It describes how sound behaves after it has already been produced inside a room—how long the sound energy continues through multiple reflections after the speaker stops.

A room can have excellent sound insulation and still be acoustically uncomfortable because speech continues reflecting from its walls, floor, ceiling, glass, and furniture.

This distinction is important because a conventional fit-out checklist may address sound separation without requiring a reverberation-time or speech-intelligibility assessment. Whether reverberation is tested depends on the project brief, applicable standard, certification target, and acoustic consultant’s scope.

The number that describes it: RT60

Reverberation time is commonly written as RT60 or T60. It is the time required for the sound level in a room to decrease by 60 decibels after the sound source stops.

A first estimate can be made using Sabine’s equation:

The absorption term is not simply the amount of “soft-looking” material in the room. It depends on the area, absorption coefficient, frequency, mounting method, furniture, occupants, and other relevant absorption effects.

Sabine’s equation is useful during design, but it is an estimate based on assumptions about the sound field. It should not replace post-installation measurement where acoustic performance is important.

For ordinary rooms, reverberation time can be measured using the procedures described in ISO 3382-2. In practice, the full 60 dB decay is often estimated by measuring a shorter portion of the decay curve and extrapolating it.

Why excessive reverberation affects speech

Speech is made up of rapidly changing sounds. If reflections continue for too long, parts of one syllable can overlap with the next syllable.

This does not mean that every reflection is harmful. Early reflections can sometimes support speech, while later reflections can reduce clarity. Speech intelligibility is also affected by background noise, room geometry, speaker-to-listener distance, microphone placement, and the frequency-dependent behaviour of the room.

There is no universal one-second threshold at which every listener begins to experience difficulty. However, as reverberation and background noise increase, speech intelligibility can decrease and listening can require more effort.

That is why an untreated meeting room can feel tiring even when people can technically hear one another.

What good performance looks like

Design targets depend on the room’s size, use, occupancy, and applicable standard. They should therefore be treated as design criteria rather than universal legal limits.

The WELL Building Standard provides useful benchmark values, including:

Conference rooms: maximum RT60 of 0.6 seconds.
Open workspaces: maximum RT60 of 0.5 seconds.
Certain learning spaces up to 280 m³: maximum RT60 below 0.6 seconds.
Certain larger learning spaces: a different limit applies.

The 280 m³ criterion should not be described as applying automatically to every enclosed office or boardroom. WELL requirements are certification criteria and should not be confused with a universal building code.

A boardroom measuring 1.5 or 2 seconds would be substantially above many speech-room design targets, but the acceptability of any measured value depends on the room’s purpose, volume, background noise, and other acoustic factors. It is better to compare the measured result with the target specified for that particular project than to apply one number to every room.

Why modern fit-outs can make the problem worse

The finishes that create a premium visual appearance can also create a highly reflective acoustic environment.

Ordinary glass is generally a low-absorption, reflective surface. Polished concrete, stone, painted plasterboard, metal, and exposed structural surfaces can have the same general effect. Exact absorption values vary with frequency, product construction, surface treatment, and test conditions, so manufacturer test data should be used for detailed calculations.

An exposed-services ceiling can also reduce the amount of continuous ceiling absorption compared with an acoustic ceiling tile system. However, an exposed ceiling does not automatically mean poor acoustics. Acoustic clouds, baffles, spray-applied absorption, lined ductwork, and other treatments can be incorporated into the design.

Carpet, curtains, upholstered furniture, acoustic wall panels, ceiling tiles, clouds, and baffles can all contribute absorption. Their performance varies significantly according to thickness, backing, mounting, spacing, and frequency.

Under the assumptions of Sabine’s equation, if the effective absorption is approximately halved while the room volume remains unchanged, the estimated reverberation time approximately doubles. This is why absorption must be calculated rather than judged only by appearance.

Hard finishes are not automatically wrong. They simply need to be balanced with deliberate acoustic treatment.

Why hybrid meetings make it more noticeable

Reverberation has always affected in-person speech clarity. It is particularly important in modern meeting rooms because microphones capture both the direct voice and reflected sound.

Directional microphones, beamforming, close microphone placement, echo cancellation, and digital signal processing can improve the result. They cannot fully compensate for excessive reverberation, poor microphone placement, long speaker-to-microphone distances, or high background noise.

A room that sounds only mildly echoey to people sitting inside it may sound considerably worse to remote participants because the microphone is transmitting the room’s acoustic response along with the speaker’s voice.

A hybrid meeting room therefore needs more than a good display and camera. It needs suitable reverberation control, appropriate background-noise levels, correct microphone placement, and an acoustic design suited to speech.

What to check during the project

At concept stage

Ask whether the room has a stated reverberation-time or speech-acoustic target.

Also confirm whether the design is intended for face-to-face meetings, video conferencing, presentations, training, or multiple uses. These requirements may not be identical.

At interior-design stage

Review the actual finishes schedule and acoustic product data.

Do not rely only on the appearance of the room. Glass, stone, polished concrete, and exposed metal usually provide little sound absorption and should not be treated as the primary acoustic solution.

Check whether the ceiling includes acoustic tiles, clouds, baffles, spray-applied absorption, or another deliberate treatment. Review wall areas, floor finishes, curtains, furniture, and the expected occupancy condition.

Before handover

Ask whether reverberation time has been measured rather than assumed from the finishes schedule.

Measurement should be performed using an appropriate method, such as ISO 3382-2 for ordinary rooms. The room should be assessed with its intended finishes and furniture in place, with the test conditions clearly recorded.

For critical hybrid rooms, also consider background-noise measurements, microphone testing, and a speech-intelligibility assessment where appropriate.

The point

A room can pass its sound-insulation test and still be acoustically uncomfortable.

Sound insulation controls sound travelling between spaces. Reverberation controls how sound behaves within a space. They are related parts of building acoustics, but they are not the same performance requirement.

The solution is not necessarily to remove every hard finish. It is to define the intended acoustic performance, calculate the room properly, select products using reliable test data, coordinate the treatment with the interior design, and verify the result after installation.

As with many fit-out problems, acoustic performance is generally less expensive to achieve during design than to retrofit after the room has been completed and furnished.

AcouBIM Engineering is an acoustic consultancy and BIM coordination practice based in Ajman Free Zone, working across the UAE and Saudi Arabia. If a space you are designing or fitting out needs its acoustics calculated rather than assumed, contact:

info@acoubim.com · +971 58 563 0037 · www.acoubim.com

References

WELL Building Standard — Reverberation Time, Feature 78. Provides benchmark reverberation-time requirements for conference rooms, open workspaces, and specified learning spaces.
ISO 3382-2:2008, Acoustics — Measurement of Room Acoustic Parameters — Part 2: Reverberation Time in Ordinary Rooms.International measurement standard for reverberation time in ordinary rooms.
Bradley, J. S., “Acoustical Design of Rooms for Speech,” National Research Council Canada, Construction Technology Update No. 51.Covers reverberation, background noise, early and late reflections, speech intelligibility, and teleconferencing rooms.
Long, Marshall, Architectural Acoustics, 2nd edition, Academic Press/Elsevier. A comprehensive professional reference covering room acoustics, sound absorption, speech rooms, building acoustics, and acoustic measurement.
Bruel & Kjær, Measurements in Building Acoustics. Practical guidance on reverberation-time measurement and the relationship between room acoustics and speech intelligibility.