What is Sound Reduction Index (SRI)? A Guide to Acoustic Performance in Glass Partitions

In simple terms, SRI measures how effectively a partition reduces the amount of sound that passes through it. The higher the value, the better the sound insulation. This is critical in modern office environments, where controlling noise and maintaining privacy are key to productivity and wellbeing. 

At Optima, our focus on innovation has enabled us to consistently deliver industry-leading acoustic performance. Having introduced frameless glass partitioning to the UK market over 30 years ago, we continue to develop systems that push acoustic standards forward. 

How is Sound Reduction Index (SRI) measured? 

The Sound Reduction Index is determined through laboratory testing of a partition system under controlled conditions. A full partition sample is installed between two acoustically isolated chambers, and sound is transmitted from one side to the other. 

The difference in sound levels between the two spaces is measured and expressed as a single-number value in decibels (dB), known as the weighted sound reduction index (Rw). Testing is carried out in accordance with EN ISO 10140-1 and 2, with results weighted in line with EN ISO 717-1. 

This standardised approach allows for accurate, like-for-like comparisons between different glass partition systems. 

Why SRI matters when specifying glass partitions 

For specifiers, the SRI (Rw dB) value provides a clear and reliable way to compare acoustic performance across systems. However, not all test data is equal. 

To ensure results are meaningful, it’s essential that: 

• The test sample represents a full partition system, not a smaller ‘window’ opening  

• The configuration includes glazing joints and perimeter track-work  

• Testing is carried out in an accredited laboratory  

Testing smaller samples can produce artificially high results, which may not reflect real-world performance. This is why understanding how the SRI value has been achieved is just as important as the number itself. 

All of our systems are fully tested in UK laboratories using full-height, multi-module configurations, ensuring results are both accurate and representative. 

From laboratory performance to real-world results 

While SRI provides a reliable benchmark, it’s important to recognise that on-site performance can be influenced by other factors, such as installation quality and flanking transmission through surrounding elements. 

This is why a complete system approach is essential. Acoustic performance is not just about the glass—it includes doors, seals, junctions, and overall system design. 

At Optima, we place equal importance on product design, testing, and installation to ensure that the performance achieved in the laboratory translates as closely as possible into real-world environments. 

Delivering industry-leading acoustic performance 

Our continued investment in research, development, and acoustic testing has enabled us to create glass partitioning systems that deliver exceptional sound insulation performance. 

We understand that modern office environments demand flexible spaces that support both collaboration and privacy. As a result, there is an increasing need for meeting rooms and quiet spaces where sound can be effectively controlled. 

By focusing on the full system—including advanced door sealing technology—we are able to achieve acoustic performance levels that rival traditional solid constructions, while maintaining the openness and transparency of glass. 

A standard you can rely on 

The Sound Reduction Index remains the most important metric when assessing the acoustic performance of glass partitions. When correctly tested and properly applied, it provides a clear indication of how a system will perform. 

By combining rigorous testing, innovative design, and proven installation methods, we continue to lead the way in delivering high-performance acoustic glass partitioning systems.