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EGT Digital is an international technology company with large teams in an open-space office. Mixed departments – designers, lawyers and programmers – share one space.
Everything said in one team could be heard and understood in the next, even though the ceiling already had acoustic treatment. There was no vertical separation between the teams – the existing desk dividers were low and had no sound absorption.
The client also had a condition: an employee standing up must be able to see colleagues. They also did not want the existing desks and dividers removed.
We measured the office according to ISO 22955:2021 “Acoustics — Acoustic quality of open office spaces”. For a space with mixed departments we applied the following target values:
| Parameter | Target | Measured before |
|---|---|---|
| Reverberation time, 125 Hz | ≤ 0.8 s | 0.65 s – yes |
| Reverberation time, 250 Hz – 4 kHz | ≤ 0.5 s | 0.45 s – yes |
| Spatial decay rate of speech D2,S | ≥ 7 dB | 4.9 dB – no |
| Speech level at 4 m, Lp,A,S,4m | ≤ 47 dB | 54 dB – no |
Conclusion: the ceiling absorbs enough and the echo in the speech range is below the target. The problem is direct speech travelling over the desks.
To be as accurate as possible, we measured the sound absorption of all surfaces on site with the Sonocat intensity probe. With this data we built a computer model of the office in Treble.
The model differed from the measurements by up to 0.14 s in reverberation time, 0.7 dB in D2,S and 2.3 dB in the level at 4 m. We used these differences to correct the expected results and compared several layout and height options.
The chosen option: suspended PET screens above the existing dividers in the two busiest zones. The height was chosen so that a seated employee is in an acoustic “shadow”, while a standing one can see across the room.
Before production we showed the client 3D visualisations of the positions, heights and colours of the screens. Once agreed, we made them in our own workshop and suspended them from the ceiling above the existing dividers, without removing any furniture.
| Parameter | Target | Before | After |
|---|---|---|---|
| Spatial decay rate of speech D2,S | ≥ 7 dB | 4,9 dB | 7.0 dB – yes |
| Speech level at 4 m, Lp,A,S,4m | ≤ 47 dB | 54 dB | 47.3 dB – borderline |
| Reverberation, 250 Hz – 4 kHz | ≤ 0.5 s | 0,45 s | 0.43 s – yes |
| Reverberation, 125 Hz | ≤ 0.8 s | 0,65 s | 0.64 s – yes |
The “after” values come from the calibrated model. The control measurement after installation confirmed them within 1–5%.
The level of a neighbouring conversation at 4 m dropped by about 7 dB, and the spatial decay rate of speech reached the target.
Similar project? See our service Acoustics and Soundproofing for Offices or contact us via the enquiry form.
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