"Blocking sound" and "absorbing sound" are fundamentally different approaches. Why does a room still echo after installing sound-insulating walls? Why can you hear the next room despite putting up acoustic panels? Understanding this distinction solves the confusion — and saves both time and frustration.
Sound Insulation vs Sound Absorption — Side by Side
| Category | Sound Insulation (Blocking · STC) | Sound Absorption (Absorbing · NRC) |
|---|---|---|
| What it does | Prevents sound from passing through walls | Prevents sound from bouncing around inside a room |
| Metric | STC (Sound Transmission Class) | NRC (Noise Reduction Coefficient) |
| Principle | Reflects & blocks sound energy | Converts sound energy to heat |
| Materials | Concrete, gypsum, mass-loaded vinyl | PET 패널, 목모보드, 멜라민폼 → PET 두께별 흡음계수 차이 보기 |
| Standard | DIN 4109 (≈ ISO 717-1) | DIN 18041 (≈ ISO 11654 / ISO 3382) |
| Location | Inside walls, under floors | Walls, ceilings, partitions |
"Confusing sound insulation and absorption doubles the effort and halves the effect."
DIN 18041 (≈ ISO 11654 / ISO 3382)
DIN 18041 (≈ ISO 11654 / ISO 3382) is the practical guideline for sound absorption: Group A rooms require mid-to-long range speech intelligibility (meeting rooms, lecture halls, classrooms — reverberation time T must be controlled). Group B rooms need short-range noise reduction (open offices, corridors, cafeterias — A/V ratio guidelines apply).
"Most offices fall under DIN 18041 (≈ ISO 11654 / ISO 3382) Group B4 — A/V ≥ 0.25, meaning at least 0.25 m² of equivalent absorption area per cubic meter of room volume."
NRC vs STC — Quick Reference
| Category | NRC (Absorption) | STC (Sound Insulation) |
|---|---|---|
| Range | 0.00 – 1.00 | 25 – 65+ |
| What It Means | Proportion of sound absorbed | Decibels blocked by partition |
| "Good" Threshold | 0.75+ | 50+ |
| What It Measures | Room reverberation reduction | Wall/floor transmission blocking |
| Standard | DIN 18041 (≈ ISO 11654 / ISO 3382) | DIN 4109 (≈ ISO 717-1) |
| Best For | Call centers, open offices | Meeting rooms, executive offices |
3 Common Mistakes
Mistake 1: Thinking sound insulation and absorption are the same
Acoustic panels on a wall will not stop sound from reaching the next room. To block transmission through walls, you need insulating structures (mass, air gaps, decoupling). These are two separate solutions for two separate problems.
Mistake 2: Expecting absorption alone to make a room silent
Absorption reduces reverberation and echo — not external noise. If traffic noise or HVAC rumble is the issue, start with windows and insulation (DIN 4109 (≈ ISO 717-1) territory). Absorption handles the internal reflections that make voices hard to understand.
Mistake 3: Ignoring low frequencies
Thin panels only absorb high frequencies. Low-frequency noise (HVAC rumble, distant traffic) requires thicker panels (24 mm+). DIN 18041 (≈ ISO 11654 / ISO 3382) mandates checking absorption across 250–2,000 Hz, not just the high end.
Reverberation Time (T60) and NRC — The Connection
Reverberation time (T60) is how long it takes for sound to decay by 60 dB after the source stops. In an untreated office, T60 can exceed 1.5 seconds — making conversations muddy and tiring. Adding materials with high NRC values reduces T60 by increasing the room's total absorption area. DIN 18041 (≈ ISO 11654 / ISO 3382) Group B4 targets enough absorption to keep T60 comfortable for all-day work.
In simple terms: NRC tells you how good a material is at absorbing. T60 tells you whether the room has enough absorption overall. You need high-NRC materials covering sufficient area to bring T60 within the target range.
올바른 흡음재 선택이 필요하신가요?
토넥스 음향 자재 보기 →Frequently Asked Questions
QDoes installing acoustic panels also provide sound insulation?
Partially possible, but fundamentally different. Acoustic panels reduce indoor reverberation (echo). To block sound from passing through walls, you need insulating structures — these are separate solutions. Think of it this way: absorption is like a sponge soaking water inside a bucket; insulation is the bucket wall that stops water from leaking out.
QDIN 18041 (≈ ISO 11654 / ISO 3382) Group A vs Group B — What is the difference?
Group A rooms need mid-to-long range speech clarity — places where one speaker addresses a large audience (lecture halls A2, meeting rooms A3/A4). Here, reverberation time (T) is tightly controlled. Group B rooms focus on short-range noise reduction — open offices (B4), corridors (B2), cafeterias (B3). Here, the A/V ratio guideline applies. Most commercial spaces are Group B.
QWhat is reverberation time (T60)?
T60 is the time it takes for sound to decay by 60 dB after the source stops — essentially how long an echo lingers. Long T60 (over 1.5s) makes speech muddy; very short T60 (under 0.3s) feels uncomfortably dead. DIN 18041 (≈ ISO 11654 / ISO 3382) Group A rooms target specific T60 values based on room volume and use type.
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