Technology
Noise Reduction Standards
Quick fact
The U.S. Environmental Protection Agency established the Noise Reduction Rating (NRR) in 1979, and it remains the mandatory label for hearing protectors sold in America.
Why this is interesting
Have you ever noticed the 'NRR' number on a box of earplugs and wondered how it’s determined? That number comes from a carefully designed noise reduction standard.
Read the full explanation
Understanding Noise Reduction Standards
Noise reduction standards are like recipe books that tell testers exactly how to measure a product’s ability to block sound. For example, to get an NRR rating, earplugs are placed on a special dummy head inside a soundproof room, and engineers measure how much sound gets through at different frequencies. The result is a single number—the higher, the better. This makes it easy to compare different brands: a foam earplug with NRR 33 is generally more protective than one with NRR 25. Similarly, windows and walls are rated using Sound Transmission Class (STC), which follows a different standard but the same idea—repeatable testing so consumers know what to expect.
A deeper explanation
These standards exist because the human ear does not perceive all frequencies equally, and real-world sound is complex. Standards like ANSI S3.19 (for hearing protectors) or ISO 4869 specify exactly which test signals to use, how to position the product, and how to calculate the final rating. This ensures that a 30 dB reduction claimed by one manufacturer is measured the same way as by another. For active noise cancellation (ANC) in headphones, standards such as the “Industry Standard for ANC Performance” (often based on tests using a manikin and diffuse-field microphones) quantify how much ambient noise is removed. Without standards, marketing claims would be meaningless. They empower consumers to make informed decisions and help regulators set safety limits, like the 85 dB/day exposure threshold in workplaces.