In the world of acoustical testing, consistency is key. Whether you’re developing a new wall system, optimizing a floor-ceiling assembly, or seeking third-party verification for building product performance, you rely on trustworthy, repeatable data.
But how do you know that results from one lab are truly comparable to another? That’s what interlaboratory studies (ILS) are for.
At NGC Testing Services, we participate in these rigorous, collaborative studies not just to validate our own practices, but to help ensure consistency across the industry.
What Is an Interlaboratory Study?
Interlaboratory studies are large-scale test comparisons coordinated by organizations like ASTM International. These studies are designed to ensure that standardized test methods (like ASTM E90 or ASTM E492) produce consistent, reliable results across different testing labs.
ASTM invites qualified laboratories to participate in these studies, sending identical materials to test the same assembly. Once the test is conducted, data is collected, anonymized, analyzed, and compiled into a final report.
These results inform precision and bias statements, which are required additions to the published test standard.
These results give clients confidence that testing at different labs should provide similar or the same results. This is essential for those trying to determine product performance, demonstrate code compliance, or meet certification goals. In addition, the results also yield repeatability and reproducibility limit values, offering clients valuable insight when interpreting their test data.
NGC Testing Services’ Recent Participation in Two Key Interlaboratory Studies
Recently, NGC Testing Services was invited to participate in two key ASTM ILS programs to update the precision and bias statements in the ASTM E90 and ASTM E492 standards.
1. ASTM E90: Sound Transmission Class Testing – ILS# 1155
Over the past year, NGC Testing Services participated in an ASTM-administered interaboratory study for ASTM E90, the standard test method for measuring airborne sound transmission loss in building partitions. This is the basis for Sound Transmission Class (STC) ratings that are used across residential, commercial, and institutional building sectors.
As one of the 15 laboratories participating in this study, NGC Testing Services was instructed to build two light-gauge steel stud wall assemblies with expected ratings around STC 50, using the same materials as the other participants. The team then performed standard testing procedures to measure how well the assembly blocked airborne sound.
Once completed, all results were combined, analyzed to assess consistency, and used to inform the official precision and bias statement for ASTM E90.
For NGC Testing Services, it was an opportunity to validate the performance of our acoustical chamber, ensure alignment with peers, and reinforce the integrity of our test data.
2. ASTM E492: Tapping Machine Floor Assembly Testing – ILS #1392, 1393, 1394 & 1395
We’re currently participating in other ASTM-administered interlaboratory study programs for floor-ceiling specimens utilizing multiple test standards, including ASTM E492, E2179, E90, and E989. ASTM E492 and E2179 are standard test methods used to measure impact sound transmission in floor-ceiling assemblies using a tapping machine. The standards are the basis for Impact Insulation Class (IIC) and Delta Impact Insulation Class (Delta IIC) ratings, respectively.
As one of the nine laboratories invited to participate in these ILS programs, NGC Testing Services again received the same test materials to assemble the same floor-ceiling system as the other participating labs. Once testing is complete and the results are compiled, ASTM will use the data to develop a new or updated precision and bias statements.
Being selected as part of this study allows us to continue evaluating the reliability of our testing methods, identify potential improvement areas, and ensure we stay aligned with other leading acoustic testing labs.
Why Interlaboratory Studies Benefit Labs Like Ours
Interlaboratory studies provide a valuable benchmark that helps a lab assess the accuracy and consistency of its results compared to peer laboratories under standardized conditions.
If a lab consistently measures higher or lower than others, it could suggest a difference in environmental conditions, calibration, or testing procedures.
Our participation in these studies shows that our testing methods, equipment, and results stand up to industry standards, giving our clients confidence that the testing we perform is accurate and consistent.
“Participating in interlaboratory studies gives us confidence that our methods are sound and our results are reliable. It’s not just about comparison. It’s about continuously validating our quality control processes and holding ourselves to the highest standard.”
– Mike Rizzo, General Manager, NGC Testing Services
Repeatability and Reproducibility: Why an ILS Matters for Clients
There are two terms you’ll often hear in the context of interlaboratory studies: repeatability limits and reproducibility limits.
Repeatability limit refers to the difference between repetitive test results by the same operator in the same laboratory. Reproducibility limit refers to the difference between two independent test results by different operators in different laboratories.
Together, repeatability and reproducibility limits tell clients what kind of variability to expect — and how confident they can be in the test results they’ve received. When clients choose a lab that participates in an ILS, they’re choosing to work with a partner committed to providing data that they can trust.
“When every lab reports results that are both consistent and accurate, it gives clients the assurance they need to move forward with confidence. Interlaboratory studies help make that possible.
– Mike Rizzo, General Manager, NGC Testing Services
The Bigger Picture: ILS and Industry Integrity
The ultimate goal of an ILS is to promote standardization and trust across all laboratory testing. When you work with a lab that participates in these studies, you’re choosing transparency over mere marketing hype. You’re choosing results that stand up to scrutiny and can be compared with confidence.
At NGC Testing Services, we take that responsibility seriously. We’re proud to contribute to interlaboratory studies that shape and strengthen acoustical testing standards for the entire industry.
Our Commitment to Quality and Consistency
At NGC Testing Services, we don’t perform field testing. Instead, we specialize exclusively in laboratory testing, and we do it with precision. Our lab is built for strict environmental control, and our team is committed to continuous improvement in everything we do.
Participating in interlaboratory studies is just one of the ways we uphold that commitment. These studies help ensure that every result we deliver reflects not only our internal standards but also industry-wide benchmarks for accuracy and consistency.
So, whether you’re developing a new product, pursuing code compliance, or comparing third-party lab options, you can trust that choosing NGC Testing Services means choosing reliable, repeatable, and validated data — every time.
Ready to get started or have questions about acoustical testing? Contact us to get started.