There is a wealth of acoustical laboratory test data published by manufacturers of building products and systems. Why is this data important, and why do building code representatives and acoustical consultants need it?
The goal is to ensure high-quality sound environments in living spaces. They aim to verify that materials and systems meet acoustical performance standards to create comfortable spaces for working, living, and recreation.
By analyzing laboratory-collected acoustical data, designers can create environments that enhance living conditions and overall enjoyment. Let’s take a look at various types of acoustic single-number ratings and explore the purpose of each.
What Is Acoustical Testing?
To begin, let’s get clear on the definition of acoustical testing. Acoustical testing is the process of measuring and analyzing sound and noise levels to ensure that buildings and environments meet specific acoustic performance standards. This type of testing evaluates how well a space:
- Controls sound transmission
- Reduces noise
- Improves overall sound quality
Types of Acoustic Single Number Ratings and Their Purpose
Sound Absorption
In homes, office spaces, and other buildings, we aim for an environment where speech is clear and not muffled. Acoustical technology provides guidelines to predict this clarity.
There is a correlation between a room's sound absorption, measured by its Noise Reduction Coefficient (NRC), and speech intelligibility. Higher sound absorption reduces reverberation, which enhances the clarity of speech communication in the room.
Sound Attenuation
Ceiling grid panels in both open office and traditional office environments must effectively manage both sound absorption and sound attenuation. Therefore, it's essential to measure a ceiling panel's NRC, Ceiling Attenuation Class (CAC), and Articulation Class (AC) to ensure a productive work environment.
Sound Transmission Class and Outdoor/Indoor Transmission Class
Sound Transmission Class (STC) measures how well a wall or floor/ceiling structure insulates against noise from adjacent spaces. Outdoor/Indoor Transmission Class (OITC) measures how effectively a window, door, or exterior assembly blocks external noise.
Higher STC or OITC ratings indicate better noise insulation, meaning less noise will penetrate a room from outside sources.
Impact Insulation Class
Impact Insulation Class (IIC) measures noise transmitted from a room to the room directly below it, such as the impact noise of hard soled shoes or boots. A higher IIC rating indicates better insulation against impact noise, reducing the disturbance of footfall or other vibrations in the room below.
Final Thoughts
Before introducing new equipment or materials into an existing acoustical environment, its sound power must be measured and characterized. High noise levels in work or living areas can be distracting and harmful to hearing.
An acoustical engineer must consider these factors when designing a space. Comprehensive testing and objective metrics are essential for evaluating a room's acoustical quality. As the Riehle Axiom states, "One test is worth a thousand expert opinions."
NGC Testing Services offers a range of acoustical tests for the building products industry. With nine test chambers, we are North America's largest and most comprehensive lab for building acoustics testing. We take pride in providing this crucial service to the industry.
To learn more about our acoustical testing services, reach out to our team today.
This post was originally published in September 2021 by Bob Menchetti and was updated and republished in September 2024.