### 01 – Hero
**H1:** STC Rating & Rw Rating for Acoustic Glass
**Subheading:** Understanding Sound Transmission Class and Weighted Sound Reduction Index — How Acoustic Performance Is Measured, Reported, and Applied
**Key Specs Badge:** STC · Rw · ASTM E90 · ISO 10140 · TL Curve · Third-Octave Analysis
**CTA Buttons:** [Talk to an Acoustic Engineer] [Request Technical Data]
---
### 02 – Introduction: Why Two Ratings Exist
**H2:** Why Are There Two Acoustic Ratings — STC and Rw?
When specifying acoustic glass, you will encounter two numbers: **STC** (Sound Transmission Class) and **Rw** (Weighted Sound Reduction Index). They describe the same physical property — a material's ability to reduce airborne sound transmission — but originate from **different standards systems serving different markets**:
- **STC** — predominantly **North America** (United States, Canada)
- **Rw** — **Europe, the UK, and most international specifications** (ISO system)
AcouSpace serves both USA and European markets, so our technical datasheets report **both values** for every tested glass build-up. Understanding what each rating means — and just as importantly, what it does **not** mean — prevents costly specification errors and sets realistic acoustic expectations for your project.
> **This page explains the physics and the standards. For the right glass structure to hit your target, see our [Acoustic Laminated Glass](/acouspace/products/acoustic-glass/acoustic-laminated-glass/) and [Acoustic Insulated Glass](/acouspace/products/acoustic-glass/acoustic-insulated-glass/) product pages.**
---
### 03 – The Fundamentals: Sound Transmission Loss (TL)
**H2:** The Foundation: Sound Transmission Loss (TL)
Both STC and Rw are derived from the same underlying measurement: **Sound Transmission Loss (TL)**, expressed in decibels (dB).
**TL definition:** The reduction in sound level as sound passes through a partition.
`TL = L₁ − L₂`
Where:
- **L₁** = sound pressure level in the source (loud) room
- **L₂** = sound pressure level in the receiving (quiet) room
**Key principle:** TL is **frequency-dependent**. A glass panel does not reduce all frequencies equally — its performance varies across the audible spectrum (typically measured 100 Hz – 5000 Hz). This is why a **single-number rating** (STC or Rw) is only a useful shorthand, never the complete picture.
```text
Sound Energy (Outside)
↓↓↓↓↓
┌──────────────────────┐
│ Tempered Glass │
├──────────────────────┤
│ Acoustic PVB │ ← Damping (converts vibration → heat)
├──────────────────────┤
│ Tempered Glass │
└──────────────────────┘
↓↓↓
Reduced Sound Transmission (Inside)
```
The glass-and-interlayer system **damps vibrational energy**: sound strikes the first glass lite, causes it to vibrate, the viscoelastic acoustic PVB dissipates much of that vibration as heat, and the second lite re-radiates significantly less sound. **This damping behaviour is what the TL curve — and therefore STC/Rw — quantifies.**
> **相关原理：** The role of the interlayer is covered in depth on our [Acoustic PVB Interlayer](/acouspace/technology/acoustic-technology/acoustic-pvb/) page; structural alternatives in [Acoustic SGP Interlayer](/acouspace/technology/acoustic-technology/sgp-interlayer/).
---
### 04 – STC Rating
**H2:** STC Rating (Sound Transmission Class)
**What is STC?**
**Sound Transmission Class (STC)** is a single-number rating of airborne sound insulation, defined by **ASTM E413** and measured per **ASTM E90** (Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions).
**How STC is determined:**
1. The glass specimen is mounted in an opening between two reverberant rooms.
2. Sound pressure levels are measured in 1/3-octave bands from **125 Hz to 4000 Hz**.
3. The resulting **TL curve** is compared against a standard reference contour.
4. The contour is shifted to fit the measured curve under defined rules (maximum allowed deviations).
5. The **TL value at 500 Hz** on the fitted contour = **the STC rating**.
**STC in plain terms:** A higher STC means **less sound transmitted**. Each +10 dB (e.g., STC 30 → 40) represents roughly a **tenfold reduction in transmitted sound energy**.
#### What STC Values Mean in Practice
| STC | What You Hear on the Other Side | Typical Use |
|-----|-------------------------------|-------------|
| **25–30** | Normal speech clearly understood | Inadequate for privacy |
| **30–35** | Loud speech audible, normal speech muffled | Basic partition |
| **35–40** | Loud speech barely audible, normal speech unintelligible | **Phone booths, privacy booths** |
| **40–45** | Loud speech faint, most speech inaudible | **Standard office pods, meeting pods** |
| **45–50** | Shouting barely audible | **Executive pods, recording booths** |
| **50+** | Essentially inaudible | Broadcast / high-end studios |
> ⚠️ **Critical caveat (see Section 08):** These descriptions apply to the **complete partition or enclosure**, not glass alone. The widely cited threshold **"below STC 30, voices remain intelligible"** refers to the **overall system**, which is why specifying only glass STC is insufficient.
---
### 05 – Rw Rating
**H2:** Rw Rating (Weighted Sound Reduction Index)
**What is Rw?**
**Weighted Sound Reduction Index (Rw)** is the ISO-system equivalent of STC, defined by **ISO 717-1** and measured per **ISO 10140** (Acoustics — Laboratory measurement of sound insulation of building elements).
**How Rw is determined:**
1. The specimen is tested in a two-room laboratory setup per ISO 10140-1/2.
2. TL is measured in 1/3-octave bands (typically **100 Hz – 3150 Hz**).
3. The curve is fitted to a **reference curve defined in ISO 717-1** using a **traffic-light (defect) system** — different rules from ASTM E413.
4. The resulting weighted value = **Rw**, reported in dB.
**Rw in plain terms:** Functionally the same concept as STC — **higher is better, representing greater sound reduction** — but derived through a **different contour-fitting procedure** and a **slightly different frequency range**.
#### Rw Spectrum Adaptation Terms (Important Distinction)
Unlike STC, the Rw system provides **optional adaptation terms** that make it more versatile for real noise spectra:
| Term | Meaning | When Used |
|------|---------|-----------|
| **Rw** | Weighted sound reduction index (base value) | General rating |
| **Rw + C** | Rw + spectrum adaptation term C | Noise dominated by **mid/high frequencies** (e.g., speech, music, human activity) |
| **Rw + Ctr** | Rw + spectrum adaptation term Ctr | Noise dominated by **low frequencies** (e.g., road traffic, HVAC, bass) |
**For office pods and speech privacy, `Rw + C` is typically the relevant figure** — it accounts for the fact that human speech energy peaks in the mid-frequency range. This nuance is one reason European specifications often cite **Rw + C** rather than Rw alone.
---
### 06 – STC vs Rw: The Comparison
**H2:** STC vs Rw: What Is the Difference?
| Parameter | **STC** | **Rw** |
|-----------|---------|---------|
| Full Name | Sound Transmission Class | Weighted Sound Reduction Index |
| Standard Body | **ASTM** (USA/Canada) | **ISO** (Europe/International) |
| Measurement | ASTM E90 + rating per ASTM E413 | ISO 10140 + rating per ISO 717-1 |
| Reference Contour | ASTM E413 reference contour | ISO 717-1 reference curve |
| Frequency Range | 125 Hz – 4000 Hz | 100 Hz – 3150 Hz (nominal) |
| Fitting Rules | ASTM deviation rules | **Traffic-light (defect) rules** |
| Common Market | **North America** | **Europe / UK / International** |
| Adaptation Terms | Not part of STC | **Rw + C, Rw + Ctr** |
| Application | Building & enclosure acoustics | Building & enclosure acoustics |
#### Can STC and Rw Be Directly Converted?
**No — and this is the most important point in this section.**
> **STC and Rw are not directly interchangeable, and there is no universal fixed conversion formula (such as "STC 40 = Rw 40").**
Two reasons:
1. **Different reference contours and fitting rules** — the same raw TL curve can yield slightly different single-number results under ASTM vs ISO procedures.
2. **Different frequency ranges** — ASTM extends to 4000 Hz while ISO's nominal range stops near 3150 Hz, giving different weight to high-frequency performance.
**In practice,** for a typical symmetric acoustic laminated glass build-up, STC and Rw values are **often close** (e.g., within 1–3 dB), which leads some suppliers to publish "STC ≈ Rw". **Treat such equivalences as approximate engineering estimates only**, never as certified conversions. Always request the **raw 1/3-octave TL curve** — it contains the real information that both ratings merely summarise.
---
### 07 – Measurement Standards & the TL Curve
**H2:** How Acoustic Glass Is Tested
**Laboratory measurement standards referenced by AcouSpace:**
| Standard | Scope |
|----------|-------|
| **ASTM E90** | Laboratory measurement of airborne sound transmission loss of building partitions (US) |
| **ASTM E413** | Classification of sound insulation (STC rating procedure) |
| **ISO 10140-1/2** | Laboratory measurement of sound insulation of building elements (intended sound insulation) |
| **ISO 717-1** | Rating of sound insulation in buildings — airborne sound (Rw + C/Ctr) |
| **EN 12758** | Glass in building — determination of sound index difference under specific conditions |
**What a test report contains:**
- **Glass build-up** (e.g., `6T + 1.14 mm acoustic PVB + 6T`)
- **Specimen dimensions and mounting condition**
- **1/3-octave TL curve** (100/125 Hz → 3150/4000 Hz)
- **Derived STC and/or Rw values**
- **Laboratory accreditation** (third-party, e.g., SGS, Intertek)
> **For our full evidence base and sample reports, see [Acoustic Glass Testing](/acouspace/technology/acoustic-technology/acoustic-testing/).**
#### Reading a TL Curve
```text
TL (dB)
50 | * (coincidence dip)
| * *
40 | * * ←── Rw / STC read near 500 Hz
| * *
30 | * *
| * *
20 | * *
+-----+-----+-----+-----+-----→ Frequency (Hz)
100 250 500 1000 2000 4000
```
**Key features:**
- **Mass law region (low freq):** TL rises ~6 dB per doubling of mass — thicker glass = better low-frequency insulation.
- **Coincidence dip:** A dip where the bending wavelength in the glass matches the acoustic wavelength in air. **Asymmetric glass thicknesses** (e.g., 6 mm + 8 mm) shift this dip away from the critical speech band (500–4000 Hz), a core technique in [Acoustic Laminated Glass Technology](/acouspace/technology/acoustic-technology/acoustic-laminated-glass-technology/).
- **Damping effect (mid/high freq):** The acoustic PVB fills in the coincidence dip and raises mid-high frequency TL — this is the **primary acoustic advantage** of acoustic PVB over standard PVB.
---
### 08 – Critical Distinction: Glass STC ≠ Complete System STC
**H2:** ⚠️ Glass STC ≠ Complete Enclosure STC
**This is the single most important concept on this page — and the source of most specification errors.**
> **The STC rating of a glass panel should not be interpreted as the STC rating of the complete office pod, meeting room, or partition wall.**
A complete enclosure's acoustic performance is the sum of **many weak links**, not the glass alone:
```text
COMPLETE OFFICE POD / PARTITION
┌─────────────────────────────────────┐
│ │
│ GLASS WALL │
│ STC 43–45 ← best element │
│ │
│ DOOR │
│ STC 38–42 ← weak link │
│ │
│ SEALS / JAMBS / HEAD │
│ STC 35–40 ← flanking │
│ │
│ CEILING PLENUM │
│ (no barrier = total leak) │
└─────────────────────────────────────┘
↓
Overall Pod STC ≠ Glass STC
(typically 3–6 dB LOWER than glass alone)
```
**Why the gap exists:**
- **Doors** — the door leaf and perimeter seals are almost always the weakest acoustic point.
- **Seals and gaskets** — any air path (jamb, head, threshold) transmits sound directly, bypassing the glass entirely.
- **Ceiling plenum** — without an acoustic barrier above the head channel, sound simply goes *over* the wall (flanking).
- **Mounting condition** — laboratory tests use idealised edge supports; real installations may differ.
**Rule of thumb:** A well-designed complete pod typically achieves an **overall STC 3–6 dB lower than the bare glass panel**. This is why AcouSpace provides **system-level calculation support**, not just glass test data — and why we always ask for your **complete enclosure drawing**, not only the glass specification.
> **See practical application:** [Acoustic Glass for Meeting Pods](/acouspace/applications/acoustic-glass-applications/meeting-pods/) and [Acoustic Glass Partitions](/acouspace/applications/acoustic-glass-applications/acoustic-glass-partitions/) discuss system integration and sealing strategy.
---
### 09 – Laboratory Results vs Real-World Performance
**H2:** Laboratory Test vs Real-World Performance
| Aspect | **Laboratory** | **Real Project** |
|--------|---------------|------------------|
| Conditions | Controlled, reverberant rooms | Actual installation on-site |
| Specimen | Defined, isolated test coupon | Complete pod / wall with doors & seals |
| Standard | ASTM E90 / ISO 10140 | Installation-dependent |
| Result | **Glass performance** | **System performance** |
| Reproducibility | High (accredited lab) | Variable (workmanship, site conditions) |
**Bottom line:** Laboratory TL/STC/Rw values represent the **tested glazing configuration under specified conditions**. The final acoustic performance of an office pod, partition, or booth depends on the **complete enclosure** — glass, frame, seals, door, ceiling transition, and installation quality.
**This is why AcouSpace:**
1. **Publishes lab test reports** for every specified glass build-up (transparency & traceability).
2. **Provides system calculation support** to predict complete-pod performance.
3. **Recommends acoustic detailing** (gaskets, drop seals, plenum barriers) to close the lab-to-reality gap.
> **This is not a disclaimer — it is the technically correct way to apply acoustic data**, and it is exactly what experienced procurement engineers and acoustic consultants expect to see.
---
### 10 – How to Select the Right Target STC / Rw
**H2:** How to Select the Right Acoustic Target
Use this decision guide to map your application to a realistic glass + system target:
| Your Application | Speech-Privacy Need | Recommended **System** Target | Typical **Glass** Starting Point |
|-----------------|--------------------|------------------------------|----------------------------------|
| Phone booth / privacy booth | 1-on-1 calls, short duration | **STC 35–40 / Rw ~35–40** | 5+0.76PVB+5 or 6+1.14PVB+6 |
| Office pod / focus room | Confidential 1–2 person work | **STC 40–43 / Rw ~40–43** | 6+1.14PVB+6 |
| Meeting pod (2–6 people) | Group calls, HR/private talks | **STC 43–47 / Rw ~43–47** | 8+1.52PVB+8 or 6+16Ar+8 |
| Executive / boardroom | Maximum privacy | **STC 47–50 / Rw ~47–50** | Composite: laminated + IGU |
| Recording / podcast booth | Full-frequency control | **STC 48–55 / Rw ~48–53** | Laminated IGU, asymmetric, triple options |
**Selection steps:**
1. **Define the privacy requirement** (who is listening, how far away, what speech level).
2. **Set the *system* target STC/Rw** — not the glass target. Add 3–6 dB to back-calculate the glass requirement.
3. **Choose the glass structure** (laminated for damping, IGU for mass+cavity, composite for maximum performance). See [Acoustic Laminated Glass](/acouspace/products/acoustic-glass/acoustic-laminated-glass/) and [Acoustic Insulated Glass](/acouspace/products/acoustic-glass/acoustic-insulated-glass/).
4. **Detail the non-glass elements** — door seals, perimeter gaskets, ceiling plenum barrier. These determine whether you *achieve* the lab figure on-site.
5. **Request a system calculation** from our engineering team before finalising the BOQ.
> **Need thermal performance too?** Combine acoustic glass with a Low-E coating — see [Low-E Acoustic Glass](/acouspace/products/acoustic-glass/low-e-acoustic-glass/) and the cavity/insulation principles in [Acoustic Insulated Glass Technology](/acouspace/technology/acoustic-technology/acoustic-insulated-glass-technology/).
---
### 11 – Frequently Asked Questions
**H2:** Frequently Asked Questions
1. **What is the difference between STC and Rw?**
STC is the North American/ASTM rating; Rw is the European/ISO rating. Both measure airborne sound insulation from a TL curve, but use different reference contours, fitting rules, and frequency ranges — so they are **not directly convertible**.
2. **Is STC 40 the same as Rw 40?**
**No.** They are often close (within ~1–3 dB for typical glass), but "STC 40 = Rw 40" is **not** a certified conversion. Always request the raw TL curve for the exact build-up.
3. **Which should I specify — STC or Rw?**
Use the standard required by your **target market / governing specification**: **STC for USA/Canada**, **Rw (often Rw + C) for Europe and international projects**. AcouSpace reports both.
4. **What STC do I need for speech privacy?**
For normal conversation to be unintelligible outside, target a **complete-system STC of at least 40**; STC 35–40 is the common threshold. Remember: this is the *system* figure, not glass alone.
5. **Does a higher STC always mean better glass?**
Within the same mounting and frequency range, yes. But STC is a single-number summary — compare the **full TL curves** when performance at specific frequencies (e.g., low bass or HVAC noise) matters.
6. **Why does my pod test lower than the glass STC?**
Because doors, seals, and ceiling/flanking paths dominate the weak links. A complete pod typically measures **3–6 dB below** the bare glass panel rating.
7. **Can acoustic PVB really improve STC?**
Yes — the viscoelastic acoustic PVB raises the **coincidence-frequency TL** and adds damping, particularly in the 1000–4000 Hz speech band. See [Acoustic PVB Interlayer](/acouspace/technology/acoustic-technology/acoustic-pvb/) for the mechanism.
8. **Does triple glazing always beat double glazing?**
**No.** Acoustic performance depends on thickness, cavity width, asymmetry, and interlayer — not simply the number of lites. A well-designed double-glazed unit can outperform a poorly specified triple unit. See [Double Glazing](/acouspace/technology/acoustic-technology/double-glazing/) and [Triple Glazing](/acouspace/technology/acoustic-technology/triple-glazing/).
9. **Are test reports available for each glass build-up?**
Yes — lab test reports (ASTM E90 / ISO 10140), 1/3-octave TL curves, and declarations of performance are supplied per project. See [Acoustic Glass Testing](/acouspace/technology/acoustic-technology/acoustic-testing/).
10. **Can AcouSpace help me calculate the complete-pod STC?**
Yes. Send your drawing, target STC/Rw, and hardware/frame details. Our engineering team models the full system and recommends the glass build-up. [Request technical data →](#final-cta)
---
### 12 – Final CTA
**H2:** Need Help Selecting the Right Acoustic Target?
Send us your required **STC / Rw target**, glass dimensions, pod/partition design, or existing specification. Our acoustic engineering team can:
- ✅ Recommend the optimal glass build-up (laminated / insulated / composite)
- ✅ Provide **lab test reports and 1/3-octave TL curves**
- ✅ Model **complete-system performance** (glass + frame + seals + door)
- ✅ Supply **technical datasheets and calculation notes** for your acoustic consultant
📩 **Email your specification to:** [sales@jumbotemperedglass.com](mailto:sales@jumbotemperedglass.com)
📞 **Or call:** +86-XXX-XXXX-XXXX
[Request a Quote] [Request Technical Data] [Talk to an Acoustic Engineer]
---
## 🔗 内部链接组（Topic Cluster）
### 下游 → Products（原理 → 产品落地）
- [Acoustic Laminated Glass](/acouspace/products/acoustic-glass/acoustic-laminated-glass/)
- [Acoustic Insulated Glass](/acouspace/products/acoustic-glass/acoustic-insulated-glass/)
- [Acoustic Laminated Insulated Glass](/acouspace/products/acoustic-glass/acoustic-laminated-insulated-glass/)
- [Low-E Acoustic Glass](/acouspace/products/acoustic-glass/low-e-acoustic-glass/)
- [Low-Iron Acoustic Glass](/acouspace/products/acoustic-glass/low-iron-acoustic-glass/)
- [Custom Acoustic Glass](/acouspace/products/acoustic-glass/custom-acoustic-glass/)
### 下游 → Applications（原理 → 场景落地）
- [Acoustic Glass for Office Pods](/acouspace/applications/acoustic-glass-applications/office-pods/)
- [Acoustic Glass for Phone Booths](/acouspace/applications/acoustic-glass-applications/phone-booths/)
- [Acoustic Glass for Privacy Booths](/acouspace/applications/acoustic-glass-applications/office-privacy-booths/)
- [Acoustic Glass for Work Pods](/acouspace/applications/acoustic-glass-applications/work-pods/)
- [Acoustic Glass for Meeting Pods](/acouspace/applications/acoustic-glass-applications/meeting-pods/)
- [Acoustic Glass for Recording Booths](/acouspace/applications/acoustic-glass-applications/recording-booths/)
- [Acoustic Glass for Podcast Booths](/acouspace/applications/acoustic-glass-applications/podcast-booths/)
- [Acoustic Glass Partitions](/acouspace/applications/acoustic-glass-applications/acoustic-glass-partitions/)
### 平行 → Technology 专题（互相锚文本引用）
- [Acoustic Technology Hub](/acouspace/technology/acoustic-technology/)（父级回链）
- [Acoustic PVB Interlayer](/acouspace/technology/acoustic-technology/acoustic-pvb/)
- [Acoustic SGP Interlayer](/acouspace/technology/acoustic-technology/sgp-interlayer/)
- [Acoustic Laminated Glass Technology](/acouspace/technology/acoustic-technology/acoustic-laminated-glass-technology/)
- [Acoustic Insulated Glass Technology](/acouspace/technology/acoustic-technology/acoustic-insulated-glass-technology/)
- [Double Glazing for Acoustics](/acouspace/technology/acoustic-technology/double-glazing/)
- [Triple Glazing for Acoustics](/acouspace/technology/acoustic-technology/triple-glazing/)
- [Acoustic Glass Performance](/acouspace/technology/acoustic-technology/acoustic-glass-performance/)
- [Acoustic Glass Testing](/acouspace/technology/acoustic-technology/acoustic-testing/)
### 反向（Products / Applications 页底部应加）
> **Technology:** [STC & Rw Ratings](/acouspace/technology/acoustic-technology/stc-rating-rw-rating/) · [Acoustic PVB](/acouspace/technology/acoustic-technology/acoustic-pvb/) · [Acoustic Testing](/acouspace/technology/acoustic-technology/acoustic-testing/)
