The Open Office Paradox: We Removed Walls for Communication — and Lost Focus

In meetings with facilities and general affairs managers at large corporations, one complaint comes up more than any other: "We spent a fortune converting to an open office to foster collaboration — and now employees just put in earphones and communicate over messaging apps."

The assumption that visual openness would naturally increase communication has collapsed in practice. Phone calls, keyboard noise, and desk-side conversations from every direction raise employees' cognitive load and fragment concentration. This is not mere inconvenience. It is an invisible cost eroding corporate productivity.

Tornex addresses this problem not through intuition, but through international standards and measured data.

The Problem Is Intelligibility, Not Volume

A quieter office is not automatically a better one. If the space is too quiet, even small sounds seem amplified and speech privacy is compromised. The goal is an optimal acoustic environment where sound is audible but its content cannot be understood.

Speech intelligibility is quantified by the STI (Speech Transmission Index). STI ranges from 0 to 1; a value near 1 means speech is perfectly intelligible, while near 0 it is incomprehensible. In open offices, the primary acoustic target is to keep the STI below 0.50 at adjacent workstations.

Acoustic measurement in Korean offices follows KS F ISO 3382-3 (Korean Industrial Standard — Acoustics: measurement of room acoustic parameters, Part 3: open plan offices — the Korean equivalent of ISO 3382-3).

This standard defines three objective metrics for how far speech travels and how clearly it is heard: STI · rD · Lp,A,S,4m.

ISO 3382-3 — Three Metrics for Measuring Open-Office Acoustics

The table below shows how ISO 3382-3's three key metrics link to real business outcomes. Class A target values follow the classification framework of Virjonen et al. (INTERNOISE 2009 / Acta Acustica 2009) and the ISO 3382-3:2022 annex criteria.

One Interruption = 23 Minutes — The Productivity Cost of Unmanaged Intelligibility

The cost of an open office with poorly managed acoustic intelligibility can be quantified. A workplace observation study by Prof. Gloria Mark of UC Irvine (CHI 2005, "The Cost of Interrupted Work") reported that recovering full cognitive depth after a single interruption takes an average of 23 minutes and 15 seconds.

This is not simply a statistic. When a single phone call from the next desk and a brief two-person exchange accumulate through the day, effective concentration time can fall below half of actual working hours.

The reason ISO 3382-3 uses STI 0.50 as its threshold is that above it, nearby conversation shifts from "audible noise" to "intelligible message" — actively consuming working memory resources.

Same Office, Different Acoustics — Separating Collaboration Zones from Focus Zones

The starting point for solving the problem is to resist making every zone equally quiet. Different areas within an office require different acoustic environments depending on their intended use.

Collaboration zones and focus zones must have different RT60 (Reverberation Time — time for sound pressure to decay 60 dB after a sound source stops) and NC (Noise Criterion — background noise rating) targets.

Tornex's Data-Driven Solution — A Three-Stage Process

Once zone-specific targets are established, Tornex applies a three-stage process to identify the most cost-effective combination of absorption, blocking, and masking. Each stage produces measurement data, making the basis for every decision fully traceable.

1. 1. On-site precision diagnosis — Per KS F ISO 3382-3, STI · rD · Lp,A,S,4m are measured zone by zone using an omnidirectional loudspeaker and microphone. Measurements are taken under actual-use conditions with furniture, occupants, and HVAC in operation to establish the baseline.
2. 2. 3D simulation — Using the specialist acoustic simulation tool Treble (Open Plan Office module), changes in furniture layout, surface materials, and ceiling absorption are modeled to predict the resulting changes in STI · rD · Lp,A,S,4m. Before any construction, we confirm whether Class A is achievable and identify the cost-optimal intervention points.
3. 3. Optimal solution delivery — Based on simulation results, absorption solutions and sound masking systems are placed at the ceiling, partition, or wall locations with the highest ROI. The same standard metrics are remeasured after installation to confirm that targets have been achieved.

Conclusion — Acoustics Is Infrastructure, Not a Finish

The conclusion is clear. The success of an open office depends not on its visible design but on the acoustic environment your ears experience. By setting zone-specific targets (STI · rD · Lp,A,S,4m) to established standards and validating through the three-stage process of diagnosis, simulation, and construction, the same space can accommodate both collaboration and focused work.

Is your office a productive environment — or a test of endurance? Experience comfort that can be proven with data.

To find out whether your office needs improvement through a quick self-assessment, refer to our brief diagnostic guide — we hope you find it useful.

Glossary

• STI — Speech Transmission Index. Ranges from 0 to 1; closer to 1 means speech is heard more clearly. Open-office adjacent-workstation target: < 0.50.
• rD — Distraction Distance. As defined in ISO 3382-3, the distance from a speaker at which STI drops below 0.50. Shorter is better; Class A target: ≤ 5 m.
• D2S — Spatial Decay Rate of Speech. The drop in sound pressure level (dB) when the distance from the speaker doubles. Class A target: ≥ 11 dB.
• Lp,A,S,4m — Speech Sound Pressure Level at 4 m. A-weighted sound pressure level at 4 m from the speaker. Class A target: ≤ 46 dB(A).
• RT60 — Reverberation Time. Time (in seconds) for sound pressure to decay 60 dB after a sound source stops. Recommended for open offices: 0.4–0.6 s.
• NC — Noise Criterion. Background noise rating, primarily used to evaluate mechanical noise such as HVAC. Typical targets: NC 35 for focus zones, NC 40 for collaboration zones.
• NRC — Noise Reduction Coefficient. Material absorption performance indicator. Average of absorption coefficients at 250 / 500 / 1k / 2k Hz, ranging 0–1. General targets: ceiling material ≥ 0.80, wall panels ≥ 0.85.
• KS F ISO 3382-3 — Korean Industrial Standard — Acoustics: measurement of room acoustic parameters, Part 3: open plan offices. Korean equivalent of ISO 3382-3; the domestic benchmark for open-office acoustic measurement.

References

All figures, standards, and research cited in this article can be verified against the following primary sources.

• ISO 3382-3:2022 — Acoustics — Measurement of room acoustic parameters — Part 3: Open plan offices
• Mark, Gonzalez & Harris, "No Task Left Behind? Examining the Nature of Fragmented Work" (CHI 2005, UC Irvine)
• Virjonen, Keränen & Hongisto, "Open plan offices — classification scheme based on ISO 3382-3 parameters" (INTERNOISE 2009)
• Harvie-Clark, Opsanger & Larrieu, "ISO 3382-3: Necessary but not sufficient" (Apex Acoustics, ICA 2019)
• Odeon — ISO 3382-3 Open plan offices (application note)
• Treble Technologies — Open Plan Office acoustic parameters
• WELL Building Standard v2 — Sound Concept