ISO 23351 for Acoustic Office Pods & Meeting Pods
Understanding ASTC, SNR & Classification for Single- and Multi-Occupant Enclosures
**Key Specs Badge:** ISO 23351-1 ｜ ASTC / D₂ₛ,₂ₘ ｜ Speech Level Reduction ｜ Class A / B / C / D ｜ SNR ｜ Complete-Pod Standard
01 – What This Page Covers
This page explains **ISO 23351** and how it applies specifically to **acoustic office pods and meeting pods**. It is written for procurement managers, specifiers, and acoustic consultants who need to understand what an "ISO 23351 Class B pod" actually means — and, just as importantly, what it **does not** mean.
The single most common source of confusion in this category is the mixing of two完全不同的（completely different）measurements:
- **STC / Rw** — measured on a **glass sample or wall element** in a laboratory (ASTM E90 / EN ISO 10140)
- **ASTC (ISO 23351)** — measured on a **complete, assembled pod or cabin** in situ
ISO 23351 does **not** certify glass. It evaluates the **entire enclosure** — glass, frame, seals, door, ceiling, floor, ventilation, and all flanking paths — for its ability to reduce speech level. Understanding this distinction is the key to specifying pods correctly and avoiding inflated marketing claims.
> **Reading time:** ~8 minutes. **Intended audience:** buyers, specifiers, acoustic consultants, pod OEMs.
02 – What Is ISO 23351?
**ISO 23351** (*Acoustics — Measurement of sound absorption in a reverberation room*) is, in its full published form, a multi-part standard. For the office-furniture and pod industry, the operative document is:
| Part | Title / Scope |
|------|---------------|
| **ISO 23351-1** | Measurement of the **sound attenuation** provided by a **single furniture element or pod** |
| ISO 23351-2 | Measurement for **rows of furniture elements** (e.g., a bank of work pods) |
In plain terms, ISO 23351-1 defines **how to measure how much quieter the outside of a pod becomes when a person is speaking inside**. The output is a **speech level reduction** value, expressed as **ASTC** (Apparent Speech Transmission Class) or, in the European convention, **D₂ₛ,₂ₘ**.
Three things ISO 23351 is **not**
1. **Not a glass standard** — It evaluates the assembled pod, not the glass component.
2. **Not a certification mark** — It is a *measurement method*. A pod is not "ISO 23351 certified"; it has been *measured in accordance with* ISO 23351.
3. **Not interchangeable with STC** — STC is a wall/glass rating; ASTC is a complete-enclosure speech-reduction rating. (See Section 07.)
> **Accurate phrasing for spec sheets and marketing:** *"Glass solutions engineered for office pods evaluated under ISO 23351-1 requirements."* **Never:** *"ISO 23351 Acoustic Glass Certification."*
03 – Why ISO 23351 Matters for Office Pods vs Meeting Pods
Office pods and meeting pods serve different acoustic purposes, and ISO 23351 captures those differences through **occupancy,声源 position, and receiver position**.
| Aspect | Office Pod (Focus / Phone Booth) | Meeting Pod |
|--------|-------------------------------|-------------|
| Typical occupancy | 1 person (occasionally 2) | 2–6 people |
| Primary sound source | One speaker — calls, dictation, focused conversation | **Multiple simultaneous voices** — discussion, video conferencing |
| Speech energy load | Lower, single-point | **Higher, distributed** |
| Critical frequency | Speech band (500–2000 Hz) | Speech band + **lower-frequency group voice** |
| Door leaf | Smaller (single, full-height) | **Wider door leaf** (often acoustic door kit) |
| Flanking risk | Ventilation opening, door seal | **Door + ceiling plenum + service cut-outs** |
| Typical ASTC target | **Class A or B** (higher privacy per occupant) | **Class A or B**, but harder to achieve due to load |
**The key takeaway:** A meeting pod with the **same ASTC** as an office pod does **more acoustic work**, because it contains multiple speakers. ISO 23351's measured speech level reduction reflects the **real occupancy scenario**, which is why the standard's test configuration must match the intended use.
04 – The Core Metrics: ASTC, SNR & D₂ₛ,₂ₘ
ISO 23351 expresses speech attenuation through three related concepts:
4.1 ASTC (Apparent Speech Transmission Class)
The single-number rating derived by fitting a speech-spectrum contour to the measured speech level reduction. Higher = better privacy. Conceptually parallel to STC, but **applied to the complete pod**.
4.2 D₂ₛ,₂ₘ (Speech Level Difference)
The **European notation** for the same underlying quantity — the difference in speech sound pressure level between the source side (inside the pod) and the receiving side (outside), measured in dB. Often reported alongside ASTC.
4.3 SNR (Speech-to-Noise Ratio) / Classification
Many pod manufacturers express ISO 23351 results as a **privacy classification** based on the residual speech level outside the pod relative to ambient noise. The commonly referenced classes:
| Class | Residual Speech Level Outside | Privacy Level | Typical Use |
|-------|-------------------------------|--------------|-------------|
| **Class A** | Barely audible, not intelligible | **Highest** | Confidential calls, HR, executive |
| **Class B** | Very low, intelligibility strongly reduced | **High** | Standard office & meeting pods |
| **Class C** | Audible but muffled | Moderate | General focus booths |
| **Class D** | Clearly audible | Low | Short-stay / decorative enclosures |
> **Important nuance:** Class boundaries and the exact SNR definition vary by manufacturer and by the ambient-noise assumption used in the test. **Always ask for the full ISO 23351 test report**, not just the letter grade. A "Class A" claim without a report is not verifiable.
05 – How an ISO 23351 Measurement Is Performed
The test is conducted on a **fully assembled pod** placed in a representative open-plan environment:
Source side (inside the pod)
- A **talker or loudspeaker** emits calibrated speech or pink-noise-like test signal
- **For office pods:** one source position (single occupant)
- **For meeting pods:** **multiple source positions** to represent distributed speakers
Receiver side (outside the pod)
- Microphones measure sound pressure level at defined **receiver positions** around the pod (typically at 1 m and at ear height of a standing/listening person)
Measurement
- Speech level difference is measured in **third-octave bands**
- Background noise and room effects are accounted for
- Result is fitted to produce **ASTC / D₂ₛ,₂ₘ** and, where applicable, a **classification**
What is deliberately included
Glass **and** frame **and** seals **and** door **and** ceiling/floor transitions **and** ventilation openings. This is precisely why ISO 23351 is a **system** standard.
> **Critical buyer insight:** A pod can have premium STC 50 acoustic glass but fail to reach Class B if the **door seal, ceiling plenum, or vent opening** is acoustically weak. ISO 23351 catches this; glass-only STC does not.
06 – Office Pod vs Meeting Pod – Test Configuration Differences
Because the two pod types are used differently, their ISO 23351 evaluation should reflect that. Reputable testing aligns the configuration to real use:
| Test Parameter | Office Pod | Meeting Pod |
|----------------|------------|-------------|
| Number of talkers | 1 (representative single user) | 2–4 (representative group) |
| Talker positions | Center / typical seated position | **Multiple positions across the footprint** |
| Door state | Closed, as used | Closed, as used |
| Furniture / occupants | Often tested empty or with 1 occupant | **Tested with representative occupants** |
| Ventilation | Operating (fan on) | Operating (fan on) |
| What is reported | ASTC / Class for single-user scenario | ASTC / Class for multi-talker scenario |
**Implication for buyers:** If you are sourcing a **meeting pod**, insist on an ISO 23351 measurement performed with **multiple talkers**. A single-talker office-pod result will **overstate** privacy for a 4-person discussion. Conversely, an office pod need not be tested as a meeting pod.
07 – ASTC vs STC – The Critical Distinction
This is the most important section on this page. Confusing ASTC and STC is the #1 error in pod specification.
| | **STC / Rw** | **ASTC (ISO 23351)** |
|---|---|---|
| What is measured | **Glass or wall element** | **Complete assembled pod** |
| Where | Laboratory (test chamber) | In-situ / representative environment |
| Standard | ASTM E90 / ISO 10140 | ISO 23351-1 |
| Input | TL curve (third-octave) | Speech level reduction (third-octave) |
| Output | STC / Rw | ASTC / D₂ₛ,₂ₘ + Class |
| Includes frame/seals/door? | **No** | **Yes** |
| Includes ventilation? | **No** | **Yes** |
The "STC gap" — why glass-only ratings overpromise
A complete pod typically loses **3–6 dB** relative to the glass-only STC through flanking paths:
| Flanking Path | Typical STC Penalty |
|---------------|---------------------|
| Frame / mullion flanking | -1 to -3 dB |
| Door perimeter & threshold | -1 to -3 dB |
| Ceiling plenum bypass | -2 to -4 dB |
| Ventilation opening | -1 to -3 dB |
**Rule of thumb:** Glass with lab **STC 47** in a well-sealed pod may deliver **ASTC in the low-to-mid 40s**. It will **not** produce ASTC 47. Any supplier claiming "STC 47 = ISO 23351 Class A" is either imprecise or misleading.
> **Accurate statement:** *"Our acoustic laminated glass achieves STC 43–45 (ASTC). When integrated into a properly sealed pod enclosure, the complete system is engineered to target ISO 23351 Class A/B — subject to full-system measurement."*
08 – The Role of Glass in an ISO 23351 Result
Glass is the **largest and most visible acoustic component** in most pods, but it is only one part of the system. To maximize the ISO 23351 result:
### 8.1 Specify the right glass build
- **Office pods:** Acoustic laminated glass 6+1.14PVB+6 (STC 41–43) is the common workhorse; 8+1.52PVB+8 for higher privacy
- **Meeting pods:** 6+1.14PVB+6 as a minimum; **asymmetric or IGU / composite builds** (6+16Ar+8, 6+PVB+6+16Ar+8) to counter the higher multi-talker load
### 8.2 Treat the door as an equal partner
The door is often the **weakest acoustic link**. A matched acoustic door leaf + perimeter compression gasket + bottom drop seal typically retains within **2–3 dB** of the wall panel.
### 8.3 Seal the flanking paths
- **Ceiling plenum acoustic barrier** above head channel
- **EPDM / acoustic gaskets** at jambs and head
- **Threshold seal** at door bottom
### 8.4 Manage ventilation
Fan and air-exchange openings are necessary for occupancy but create a direct sound path. Use **acoustic labyrinth / silencer ducts** and detail plug recommendations around grommets.
> **The engineering reality:** You cannot "buy" an ISO 23351 Class by upgrading glass alone. Class A/B requires a **disciplined system**: glass + frame + seals + door + ceiling + ventilation, all engineered together.
09 – How to Specify ISO 23351 Correctly
When writing a spec or RFQ, use this template language:
> *"The pod shall be evaluated in accordance with ISO 23351-1 for speech level reduction. The test configuration shall reflect the intended occupancy (**one talker for office pods / multiple talkers for meeting pods**). Reported results shall include ASTC (or D₂ₛ,₂ₘ), the corresponding privacy class, and a full third-octave speech level reduction curve. Glass-only STC values shall be provided separately and shall not be represented as ISO 23351 / ASTC results."*
### Questions to ask your supplier
1. Was the measurement performed on a **fully assembled pod** (ISO 23351), or on glass only (ASTM E90 / ISO 10140)?
2. **How many talkers** were used in the test — one (office) or multiple (meeting)?
3. Was the **door closed and ventilation operating** during the test?
4. Can you provide the **full report** (lab, date, configuration, third-octave data, class)?
5. What was the **ambient noise assumption** used for the classification?
10 – Common Misinterpretations – Buyer Beware
| Myth | Reality |
|------|---------|
| "Our glass is ISO 23351 certified" | **False.** ISO 23351 evaluates the complete pod, not glass. Glass has STC/Rw per ASTM E90 / ISO 10140. |
| "STC 50 = Class A pod" | **False.** Glass STC and pod ASTC are different measurements. Expect a 3–6 dB system gap. |
| "Any Class B pod is the same" | **False.** Class depends on test configuration (occupancy, ventilation, ambient noise). Compare full reports. |
| "A single-talker test covers a meeting pod" | **False.** Multiple simultaneous talkers require a multi-talker test configuration. |
| "Better glass alone guarantees Class A" | **False.** Door, seals, ceiling, and ventilation are equally decisive. |
11 – JUMBO AcouSpace Position
At JUMBO Glass Group / AcouSpace, we manufacture the **acoustic glass components** that go into office pods and meeting pods — not the complete pod enclosures. Our position is therefore precise and honest:
- **Glass performance:** Tested per **ASTM E90 / EN ISO 10140**; STC / Rw reported with **full TL curves**
- **Pod system support:** We engineer glass builds to support our customers' **ISO 23351 ASTC targets**, including asymmetric and composite constructions
- **What we do not claim:** We do **not** label our glass as "ISO 23351 certified" or "ISO 23351 Class A glass"
### Manufacturing & quality
- **20+ years** tempered / laminated / IGU export manufacturing
- **Dedicated acoustic line** — separate PVB laminating room, humidity-controlled IGU chamber
- **Jumbo capability** — flat tempered up to 2440 × 5000 mm; laminated and IGU to corresponding jumbo formats
- **CNC machining** — hinge, lock, closer, vent, and grommet cut-outs to **±0.5 mm**
- **In-house R&D** — STC / ASTC calculation and modeling support for complete systems
- **QC per batch** — 100% spark test, dimensional laser scan, sample audit
- **Certifications** — EN 12150, EN 14449, EN 14179, ANSI Z97.1, AS/NZS 2208, CCC, ISO 9001:2015
- **Third-party testing** — SGS / Intertek on request
- **Lead time** — samples 10–14 days; bulk 25–35 days FOB
12 – FAQ
**1. What is ISO 23351 in simple terms?**
It is a standard for measuring how much a complete office pod or cabin reduces speech sound. It is a **pod-level, not glass-level** measurement.
**2. What is the difference between ASTC and STC?**
STC measures a glass/wall sample in a lab; ASTC (ISO 23351) measures the whole assembled pod in use. They are not interchangeable.
**3. What does Class A / B / C / D mean?**
These are privacy classes based on how audible residual speech is outside the pod. Class A = highest privacy (barely audible, not intelligible); Class D = clearly audible. Always request the underlying report.
**4. Is "ISO 23351 certified glass" a real thing?**
No. ISO 23351 evaluates complete enclosures. Glass is evaluated per ASTM E90 / ISO 10140 (STC / Rw). Be wary of suppliers using "ISO 23351" as a glass label.
**5. Can acoustic laminated glass reach Class A in a pod?**
Glass alone does not determine class. A well-designed system using acoustic laminated or composite glass **together with** proper door, seals, ceiling, and ventilation can target Class A/B — verified by ISO 23351 measurement.
**6. Do office pods and meeting pods use the same ISO 23351 test?**
The standard method is the same, but the **configuration differs** (one talker vs. multiple talkers). Insist on a test that matches your actual use.
**7. Why does our pod with STC 47 glass not reach Class A?**
Because the complete pod loses 3–6 dB through door, frame, ceiling, and ventilation flanking. Glass STC is only one contributor to ASTC.
**8. Can JUMBO provide ISO 23351 testing?**
ISO 23351 is a complete-pod measurement, typically performed by the pod OEM or a certified acoustic lab. We provide the **glass TL/test data** and engineering support to help the complete system reach its ASTC target.
**9. What glass build do you recommend for a meeting pod?**
For multi-talker meeting pods: 6+1.14PVB+6 as a minimum, or asymmetric / IGU / composite builds (e.g., 6+16Ar+8, 6+PVB+6+16Ar+8) for higher ASTC targets. Send us your target and configuration.
**10. How do I request a quote?**
Send your pod type (office or meeting), target class / ASTC, dimensions, hardware template, and occupancy scenario to sales@jumbotemperedglass.com.
13. Final CTA
### Need Acoustic Glass Engineered for Your ISO 23351 Target?
Send us your pod configuration and ASTC / privacy-class target. Our engineering team recommends the optimal glass build — laminated, asymmetric, IGU, or composite — and supplies full TL-curve data to support your complete-pod ISO 23351 measurement.
[Request a Quote] [Download ISO 23351 FAQ] [Send Your Drawing]
📩 Email: tomron1688@gmail.com
- [Request a Quote] [Download Datasheet]
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