How Acoustic Insulation Improves STC and NRC Ratings

How Acoustic Insulation Improves STC and NRC Ratings

Understanding STC and NRC: What building owners and specifiers need to know — acoustic thermal pcr in context

Before choosing materials, it’s essential to understand the two most common acoustic performance metrics: STC (Sound Transmission Class) and NRC (Noise Reduction Coefficient). STC measures airborne sound transmission through partitions (walls, floors, ceilings) and is weighted toward speech frequencies; higher STC means less sound passes between spaces. NRC is a scalar average of sound absorption across mid-frequency bands and describes how much sound is absorbed in a room; higher NRC reduces reverberation and improves speech clarity inside a space. When you evaluate products—especially new sustainable options like acoustic thermal pcr (post-consumer recycled acoustic-thermal materials)—you should consider both metrics because they serve different acoustic goals.

How Acoustic Insulation Affects STC: Mass, seals, and assembly

Improving STC is primarily about preventing sound from traveling through a partition. Acoustic insulation contributes in three major ways: adding mass, increasing damping, and improving airtightness and structural decoupling.

• Mass: Heavier materials (mass loaded vinyl, dense boards) reduce transmitted sound energy, particularly at mid and high frequencies. Adding mass is often the most straightforward way to raise STC.
• Damping: Viscoelastic layers or damping mats (e.g., butyl rubber sound damping mat) convert vibrational energy into heat, reducing resonance in metal studs, drywall, or panels and improving STC across a wider frequency range.
• Sealing and decoupling: Gaps, flanking paths, and rigid connections dramatically lower an assembly’s STC. Using resilient channels, double-stud walls, or acoustic isolators, together with airtight seals (butyl waterproof tape, acoustic sealants), greatly enhances effective STC.

How Acoustic Insulation Affects NRC: Absorption, porosity, and thickness

NRC relates to how much sound energy is absorbed within a room, not how much passes through a partition. Porous absorbers (open-cell foams, mineral wool, sound absorbing cotton) and panel absorbers increase NRC by converting airborne sound into heat inside their structure. Key factors are:

• Porosity and fiber/foam structure: Materials with open pathways let air move and dissipate energy.
• Thickness and cavity: Thicker absorbers or those mounted with an air gap perform better at lower frequencies.
• Placement: Absorbers in reflection hotspots (ceilings, rear walls, first reflection points) maximize NRC benefit for speech and music clarity.

Material Choices: Comparing common sound insulation products including acoustic thermal pcr

Different materials optimize for STC (blocking) or NRC (absorbing). Sustainable acoustic thermal pcr materials can offer combined thermal and acoustic performance while using recycled content. Below is a practical comparison of materials often used in building and vehicle acoustics.

Table sources: ASTM standards, industry datasheets, and manufacturer technical pages (see sources list).

Design strategies: How to combine materials for the best STC and NRC

Because STC and NRC measure different behaviors, the best projects use layered strategies: for walls that must block noise (e.g., between apartments), focus on mass, cavity insulation, decoupling, and airtightness. For rooms that must sound good inside (music rooms, open-plan offices), prioritize absorptive treatments and diffusion to raise NRC and reduce reverberation.

Practical steps:

• Use MLV or additional drywall layers with butyl damping on metal panels to raise STC where blocking is primary.
• Fill cavities with mineral wool or sound absorbing white cotton (or acoustic thermal pcr batts) to improve STC and add thermal performance.
• Install surface absorbers (NBR foam, acoustic panels) where NRC needs improvement.
• Seal perimeters and use resilient mounts (resilient channels, isolation clips) to reduce flanking and improve real-world STC.

Testing and standards: Measuring STC and NRC (what specifiers should require)

Ask for lab test reports and confirm the test standards: STC is determined per ASTM E90 (laboratory measurement) and NRC is typically measured using ASTM C423 (sound absorption in reverberation room). Field performance can differ; ASTM E336 covers field sound transmission measurements. Always request test data for the specific assembly or product combination; standalone product STC/NRC numbers may not represent installed performance.

Installation pitfalls that reduce effective STC/NRC

Even high-performance materials fail if installed incorrectly. Common issues:

• Gaps and leaks at junctions: unsealed penetrations and perimeter gaps can cut STC dramatically.
• Rigid bridging: direct attachment between two sides of a partition (through metal studs or blocking) bypasses decoupling measures.
• Ignoring low-frequency transmission: many lightweight systems perform well at mid-frequencies but poorly at bass; consider mass and cavity depth or tuned absorbers for bass control.
• Using absorptive materials where blocking is needed (or vice versa): match material function to the acoustic objective.

Why choose acoustic thermal PCR materials: sustainability without sacrificing performance

Acoustic thermal PCR (post-consumer recycled) products combine thermal insulation and acoustic function while reducing environmental footprint. For projects prioritizing sustainability and acoustics—multifamily housing, offices, and automotive interiors—PCR-based absorbers and cavity fills provide acceptable NRC and contribute to thermal performance. When evaluating such products, request lifecycle data and manufacturing traceability to ensure recycled content claims are verifiable.

ASLONG (Welllink Guangdong New Material Co., Ltd.): Experience, products, and global reach

ASLONG was founded in 2000 and is a high-tech enterprise specializing in R&D, production, and sales of acoustic materials, sound insulation materials, shock-absorbing materials, and related products. With a modern production base exceeding 10,000 m², ASLONG provides efficient, environmentally friendly, and high-performance sound insulation material solutions worldwide. The company exports to Europe, North America, Asia, and Africa and serves sectors including construction, automotive, residential, industrial, and entertainment facilities.

ASLONG product overview and core advantages — acoustic thermal pcr compatibility

ASLONG’s main product categories and their core competitive strengths:

• Butyl Rubber Sound Damping Mat — high damping factor for panel resonance reduction; easy to apply on vehicle and building metal panels.
• Mass Loaded Vinyl — dense, flexible barrier for increasing STC without excessive thickness.
• NBR Foam — open-cell foam for interior absorption and vibration isolation with options tuned for NRC improvements.
• Sound Absorbing White Cotton — cavity fill with good NRC and thermal insulation; can be supplied with PCR content on request.
• Tire Silent Foam — specialized foam for automotive NVH applications.
• Butyl Waterproof Tape — sealing and bonding tape that also helps block air leakage and flanking paths.
• Electric Auxiliary Material — installation accessories and components to support acoustic solutions.

Why specifiers choose ASLONG: long operational history (since 2000), integrated R&D and production capacity, broad product range across absorption, damping, and barrier functions, and export experience to major markets. ASLONG supports sustainable options such as acoustic thermal PCR materials and can provide technical data and testing support for assemblies.

Recruiting agents worldwide — partner invitation

ASLONG is expanding global distribution and is recruiting agents and partners worldwide. If you distribute insulation or NVH materials, or specify acoustic solutions in construction or automotive markets, ASLONG offers competitive margins, technical support, and reliable production capacity. Contact ASLONG for partnership terms and product samples.

Practical checklist for project specification: ensuring STC & NRC targets are met

Follow this checklist when writing specs or tender documents:

• Define target STC and NRC values for each space type (e.g., apartment wall STC ≥ 50; classroom NRC ≥ 0.70).
• Specify tested assemblies with ASTM reports; require field verification if necessary (ASTM E336).
• Require sealing, resilient mounts, and cavity fill; list acceptable products (e.g., MLV, butyl damping, mineral wool or acoustic thermal PCR batts).
• Prescribe installation details: perimeter seal, penetrations, and junction treatments.
• Include maintenance and warranty expectations, and sustainability or PCR content if required.

Frequently Asked Questions (FAQ)

Q1: What’s more important: STC or NRC?
A1: They measure different things. Use STC to block noise between spaces; use NRC to control reverberation inside a room. Many projects require both.

Q2: Can one product improve both STC and NRC?
A2: Some composite solutions combine barrier layers (MLV), cavity absorption, and surface absorbers to improve both metrics. However, a single thin product rarely gives high performance on both.

Q3: How much STC improvement can I expect from adding MLV?
A3: Typical STC gains range from +6 to +12 depending on existing assembly and MLV weight. Ask for tested assembly results for accurate prediction.

Q4: Are acoustic thermal PCR materials effective?
A4: Yes—when designed and specified correctly. PCR-based absorbers can deliver comparable NRC and thermal benefits to virgin-fiber products; request test and lifecycle data.

Q5: Do damping mats like butyl rubber improve NRC?
A5: No, damping mats mainly reduce panel vibration and improve STC indirectly; they are not significant absorbers for room reverberation.

Contact ASLONG / View Products — CTA

Need help meeting STC or NRC targets? Contact ASLONG for technical support, test data, and samples. View our product range including Butyl Rubber Sound Damping Mat, Mass Loaded Vinyl, NBR Foam, Sound Absorbing White Cotton, Tire Silent Foam, Butyl Waterproof Tape, and Electric Auxiliary Materials. We also welcome agents worldwide — inquire today for partnership details and product catalogs.

Sources

• ASTM International — ASTM E90: Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions.
• ASTM International — ASTM C423: Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method.
• ASTM International — ASTM E336: Standard Test Method for Measurement of Airborne Sound Insulation in Buildings.
• Acoustical Society of America (ASA) — Fundamentals of architectural acoustics and measurement principles.
• Manufacturer technical datasheets for Mass Loaded Vinyl and damping mats (industry typical values).
• Noise Control Engineering: principles of mass, damping, and absorption in noise control design.