Acoustic engineering firm: measured sound comfort

French commercial acoustics is structured around the NF S 31-080 standard, which defines three levels of requirement (standard, high-performance, very high-performance) according to the type of space. For a high-performance open space, the target reverberation time remains below 0.5 seconds and the spatial decay per doubling of distance (D2,S) above 7 dB(A). Regulations require the employer to reduce noise to the lowest level reasonably possible, a principle echoed in the leading commercial guides on noise reduction in the workplace.

The consequences of poor acoustics are documented: prolonged exposure to high sound levels in an open space generates cognitive fatigue and a drop in productivity, and noise is declared the primary nuisance by employees in recent surveys on quality of life at the office published in 2023.

Our reading differs from the profession’s conventional wisdom on one specific point: the high-performance level is not always the right target. For a commercial floor with high turnover or a temporary project space, aiming for the high-performance level inflates the budget without any gain perceived by the occupants. Kytom prescribes a deliberate standard level for these typologies, and reserves the high-performance level for strategic floors (management, R&D, floors with more than 50 workstations in long-term occupation).

Kytom works on 4 critical typologies: open spaces of 50 to 200 workstations, meeting rooms of 8 to 30 seats, phone booths for 1 to 4 people and break areas. The CINOV-GIAc certified acousticians rely on the CATT-Acoustic and Odeon 3D simulation tools to ensure reliable specifications from the preliminary design phase onward.

The Kytom method: 5 phases staged over 12 weeks

The acoustic process unfolds in five staged phases, integrated into the project’s standard timeline:

1. On-site diagnostics: class 1 sound level meter, measurement of the existing RT at 6 points per floor, DnT,A between sensitive rooms, delivery within 10 days.
2. 3D modelling: simulation of absorbent materials (αw greater than or equal to 0.90 on the ceiling, 0.70 on the wall) and forecast RT calculation per octave from 125 Hz to 4,000 Hz.
3. Costed technical specifications: 72/48 double-skin partitions (Rw greater than or equal to 44 dB), suspended ceilings, baffles, phone booths certified ISO 23351-1 classes A to D.
4. Site supervision: minimum of 3 inspection visits, coordination with the HVAC package to limit equipment LAeq to 35 dB(A).
5. Adversarial acceptance measurements: within 5 days of delivery, with furniture installed, enforceable conformity report.

The project manager coordinates the acoustic engineering firm, interior architect, quantity surveyor and contractors. The MEP coordination under the raised access floor (height 100 to 300 mm, air ducts, power, VDI, condensates) integrates the structure-borne transmission constraints from the preliminary design phase onward, in close liaison with the HVAC package.

For the CFO and Asset Manager: why the acoustic package is the project’s best ROI

A dedicated acoustic package significantly improves the reverberation time and speech intelligibility (STI) in commercial spaces, directly contributing to employee comfort and productivity.

The acoustic package generally represents 5 to 8% of the fit-out budget. On a floor of 100 workstations at 12,000 EUR/workstation, this corresponds to 60,000 to 96,000 EUR, an investment whose return is measurable from the first year through reduced absenteeism and the concentration gains documented by sector studies (Actineo, ARSEG).

On a payroll of 6 to 8 M EUR per year, even a marginal gain in acoustic comfort generates a rapid return on investment, the acoustic package representing a limited fraction of the overall fit-out budget. No other package in the project offers this ratio.

Environmental certification and usage quality approaches give value to these acoustic performances, helping to improve rental appeal and asset value for the Asset Manager. Controlled sound comfort also strengthens employee satisfaction and their effective on-site presence.

Field feedback confirms the correlation between acoustic treatment and employee engagement. The adversarial acceptance report, enforceable, secures these indicators for the project owner and the occupants.

Points of attention: 4 competing parameters and conditions for non-applicability

Commercial acoustics remains a fragile balance between absorption, insulation, design and budget. Four points of vigilance structure our specifications:

• Open industrial ceilings: they require significant additional absorbent surfaces (baffles, islands) to achieve a high-performance level in an open space, with an extra cost to anticipate from the costing stage.
• Class D phone booths: their insufficient attenuation (below 20 dB) frequently generates user complaints post-delivery; Kytom prescribes exclusively classes A or B.
• Older buildings: timber floors and ceiling heights below 2.50 m can limit the DnT,A to 38 dB instead of the 44 dB targeted; complementary structure-borne work is costed from the diagnostics stage.
• Measurements without furniture: notable discrepancies appear if acceptance is carried out empty; the reports systematically require the presence of installed furniture.

When a dedicated acoustic engineering firm is NOT the right answer. Below 30 workstations on a single floor with a ceiling height above 3 m and an existing absorbent ceiling, a standardised specification from the interior architect (alphaw 0.90 on the ceiling, 72/48 single-skin partitions) is sufficient. A dedicated acoustic engineering firm becomes relevant above 50 workstations, in the presence of sensitive rooms (management, HR, executive committee) or for a contractual environmental certification target.