Room acoustics design is relevant to every interior project, but what to prioritize depends on the function of the space and the activities of its occupants. Offices need concentration and collaboration; classrooms need speech intelligibility; hospital rooms need recovery and rest; cafes need private conversation — the goal is different for each space, and "quietness" means something different in each one.
Quiet is not one thing — each room has its own answer.
Office Spaces — Balancing Concentration and Collaboration
The core function of an office is concentration and collaboration. The biggest factor disrupting concentration is the sound of colleagues' conversations, followed by external traffic noise and sounds from adjacent rooms.
In the Leesman Index survey of 350,000 employees across 2,700 workplaces, 75% of employees identified a "quiet environment" as essential to effective work — yet actual satisfaction reached only 30%.
According to the Steelcase Global Report, 66% of employees say office noise reduces their productivity, and open-office workers lose an average of 86 minutes of focused time per day to noise and interruptions. The targets are: open-office RT60 0.3–0.7 seconds and maximum background noise NC 35 or below.
Interior Design Strategy
Acoustic zoning at the layout stage — physically separating noisy zones (collaboration, phone calls) from quiet zones (focused work). Secure absorptive area through carpet, fabric seating, and breathable furniture finishes. Desks arranged in angled clusters rather than a single row are more effective at blocking direct sound.
Doors, windows, and HVAC ducts should receive sound isolation treatment (door seals + STC 35+ doors + duct liner). Lecture and presentation spaces benefit from a reflective panel behind the speaker combined with absorption facing the audience. Meeting rooms requiring speech privacy should add sound masking (white/pink noise).
Educational Spaces — Clear Speech at Every Seat
The primary goal of a classroom or lecture hall is to ensure that the speaker's (teacher's) voice is intelligibly transmitted to every seat. The main sources of interference are external road noise, noise between students, and HVAC noise.
Research has found that speech intelligibility for students in the fourth row can drop to as low as 50% in non-compliant classrooms — and the impact is greatest for young learners, language learners, and students with hearing impairments.
ANSI/ASA S12.60 Part 1 (classrooms of 10,000 cu ft or less) mandates RT60 ≤ 0.6 seconds, background noise ≤ 35 dBA, and signal-to-noise ratio (SNR) ≥ +15 dB. ASA research shows that students in classrooms meeting this standard score 12% higher on standardized tests.
Interior Design Strategy
Full ceiling acoustic treatment (NRC ≥ 0.85 ceiling tile) + rear wall absorption + partial side wall absorption (retaining some reflection). The wall behind the speaker should act as a reflector to project the voice directly to the audience.
External isolation: double glazing + door seals + STC 40+ doors; HVAC: duct liner + low-noise diffusers. Classrooms with a high proportion of young children or hearing-impaired students should additionally target a Speech Transmission Index (STI) ≥ 0.60.
Healthcare Spaces — Recovery and Clear Clinical Communication
The primary functions of hospitals and treatment rooms are patient recovery, rest, and sleep — yet at the same time, clinical staff require accurate communication and focused attention. Corridor footsteps, conversation, medical equipment alarms, and neighboring patient noise all raise blood pressure, accelerate heart rate, and delay wound healing. This was the direct rationale behind the FGI Guidelines' 2006 recommendation for single-patient rooms.
FGI Guidelines patient room criteria: NC 40 or below (HVAC and mechanical noise NC 25–30 or below), wall and door STC > 45, ceiling NRC ≥ 0.85. Multi-bed wards should reinforce inter-bed isolation with floor-to-ceiling acoustic partitions between beds.
Interior Design Strategy
Patient rooms, treatment rooms, and diagnostic rooms should be designed as acoustically independent spaces — prioritize wall, door, and window isolation (double glazing + STC 45+ doors). Ceilings: NRC 0.85 + antimicrobial, fire-rated, and cleanable finish materials.
Multi-bed wards: bed spacing ≥ 1.8 m + ceiling-to-floor acoustic partitions. Medical equipment: low-noise models preferred; enclose existing equipment if necessary. Staff lounges and nursing stations should be in separate zones with sound masking for speech privacy.
Cafes and Restaurants — Balancing Ambience with Private Conversation
The essence of a restaurant or cafe is meeting, socializing, and dining. Yet the Korean trend of exposed ceilings, hard flooring, and close table spacing is acoustically one of the worst combinations possible. Typical restaurant noise levels reach 65 dBA, peaking at 85 dBA, and in a 2018 global survey the number-one guest complaint was "noise."
The core issue is the Lombard Effect: once ambient noise exceeds approximately 45 dB, people unconsciously raise their voices, which in turn raises the background noise level further — a vicious cycle. Doubling the total acoustic absorption area (equivalent absorption area, A) through absorptive treatment can reduce noise by approximately 6 dB.
Interior Design Strategy
Physical separation of the dining area from the kitchen, bar, and restrooms is the top priority. Make full use of wall and ceiling acoustic panels (melamine foam, PET, wood wool boards, etc.) — even an exposed-ceiling concept can achieve absorptive area through acoustic ceiling rafts.
Table spacing ≥ 1.2 m + use of partitions, plants, or bookshelves to block direct sound. Open kitchens should use glass partitions. Felt pads on table and chair legs; prioritize fabric-upholstered furniture. Seat large groups in separate zones or enclosed rooms.
Acoustic Standards by Space Type — at a Glance
Based on DIN 18041:2016, ANSI/ASA S12.2-2019, ANSI/ASA S12.60-2010 R2020, and FGI Guidelines. Targets scale with room volume.
| 기준 | 공간 유형 | 목표 RT60 | 최대 NC | 핵심 설계 전략 |
|---|---|---|---|---|
| Open office | Open office | 0.3-0.7s | NC 35 | Acoustic zoning + carpet/fabric |
| Meeting room | Meeting room | 0.4-0.6s | NC 30 | STC 45+ + sound masking |
| Classroom (≤10k cuft) | Classroom (≤10k cuft) | ≤ 0.6s | NC 30 (≤35 dBA) | NRC 0.85 ceiling + rear absorption |
| Patient room (FGI) | Patient room (FGI) | 0.5-0.9s | NC 40 (HVAC ≤30) | STC 45+ + NRC 0.85 ceiling |
| Cafe / restaurant | Cafe / restaurant | 0.6-1.0s | NC 40 | Ceiling raft + 1.2m+ tables |
Priority by Situation — Where to Start
Focus zone in open office
Collab + focus combined
Meeting room speech privacy
Speech must not transmit
Classroom speech intelligibility
Reach all seats
Patient room recovery
FGI compliance
Cafe/restaurant — break Lombard cycle
Lively but conversable
In Summary — It Is Not the Same Kind of "Quietness"
Room acoustics design is not about "how quiet does it need to be" — it is about "what must be heard in this space, and what must not be." An office needs a moderate level of activity that does not interfere with concentration; a classroom needs the speaker's voice to be transmitted clearly; a hospital room needs patient rest; a cafe needs conversations at adjacent tables to be masked while those within one's own group remain audible — every space has its own answer.
Tornex provides integrated indoor acoustic management: identifying space-specific noise sources at the design stage, establishing target RT60 and NC guidelines, recommending materials, supervising construction, and conducting post-installation measurement.
Q1RT60 or NC — which matters more?
Q2Is NC 35 + RT60 0.5s realistic in open office?
Q3Does Korea have mandatory room acoustic standards?
Q4Can exposed-ceiling concepts still have absorption?
Q5When should sound masking be considered?
Glossary — Abbreviations
- RT60 (Reverberation Time) — The time it takes for sound pressure to decrease by 60 dB after a sound source stops. A measure of how much a space reverberates. Measured per ISO 3382-2.
- NC (Noise Criteria) — A family of curves for evaluating background noise by octave band (16 Hz – 8 kHz). The NC rating is the curve that the measured spectrum tangentially contacts at its highest point. ANSI/ASA S12.2.
- NRC (Noise Reduction Coefficient) — Average of absorption coefficients at 250 / 500 / 1000 / 2000 Hz. Ranges from 0 (total reflection) to 1 (total absorption). Measured per ASTM C423.
- STC (Sound Transmission Class) — Sound isolation performance rating for walls, doors, and windows. STC 35: standard door / STC 45+: conference room recommended / STC 50+: hotel guestroom. Per ASTM E413.
- STI (Speech Transmission Index) — A quantitative index of speech intelligibility. Ranges from 0 (unintelligible) to 1 (fully intelligible). Classrooms: ≥ 0.60 recommended. IEC 60268-16.
- SNR (Signal-to-Noise Ratio) — Speech level minus background noise level (dB). Classrooms: ≥ +15 dB / cafe conversation: ≥ +3 dB.
References — Primary Sources
[1] DIN 18041:2016 Audibility in Rooms — Vital-Office summary.
https://www.vital-office.net/din-18041-audibility-in-rooms-%E2%80%93-requirements-recommendations-and-advice-for-the-planning-of-offices-conference-rooms-and-classrooms
[2] ANSI/ASA S12.2-2019 Criteria for Evaluating Room Noise — The ANSI Blog. https://blog.ansi.org/ansi/ansi-asa-s12-2-2019-criteria-room-noise/
[3] ANSI/ASA S12.60 Part 1-2010 (R2020) School Acoustics — The ANSI Blog. https://blog.ansi.org/ansi/ansi-asa-s12-60-part-1-2010-r2020-school-acoustics/
[4] FGI Guidelines — Noise and Acoustics 2018 — Facility Guidelines Institute. https://www.fgiguidelines.org/wp-content/uploads/2017/11/E64_HCD2017_Acoustics.pdf
[5] Lombard Effect in Restaurants — PMC9023576 / Scientific Reports (2022). https://pmc.ncbi.nlm.nih.gov/articles/PMC9023576/
[6] Leesman Index — Noise at Work (Knoll Workplace Research). https://www.knoll.com/document/1356419744037/Knoll_NoiseAtWork.pdf
[7] Center for Health Design — Validating Acoustic Guidelines for Healthcare Facilities.