NRR and SNR in Hearing Protection
NRR and SNR in Hearing Protection
The Importance of NRR and SNR Values in BBU Safety Hearing Protection
In accordance with occupational health and safety (OHS) standards, selecting the correctpersonal protective equipment (PPE) is a critical requirement for preventing the risk of hearing loss in high-noise workspaces. When selecting BBU Safety hearing protectionproducts, the NRR (Noise Reduction Rating) and SNR (Single Number Rating) values statedon packaging and technical data sheets serve as fundamental rating standards indicating theextent to which an earplug or earmuff attenuates noise.
What Are NRR and SNR?
• SNR (Single Number Rating): A single-number noise attenuation rating used underEuropean Union standards (EN 352-2). Measured in decibels (dB), it expresses theoverall noise reduction level provided by the product.
• NRR (Noise Reduction Rating): A noise reduction rating applied according to North American standards (ANSI S3.19). It is determined through testing conducted underideal laboratory conditions.
Comparison of SNR and NRR
Although both values indicate noise reduction capacity, their testing methodologies and calculation norms differ:
|
Feature |
SNR (Single Number Rating) |
NRR (Noise ReductionRating) |
|
Regional Standard |
European / International (EN 352) |
North American (ANSI S3.19) |
|
BBU Safety Certification |
CE EN 352-2 |
ANSI S3.19 |
|
Test Method |
Closer to real-world operationalmargins |
Focused on ideal laboratoryconditions |
|
AverageAttenuation Level |
Appears approximately 2–5 dB higher than NRR |
Slightly more conservativecompared to SNR |
How to Calculate the Difference Between NRR and SNR
When calculating in-field noise exposure, the theoretical NRR or SNR values obtained underlaboratory conditions are not directly subtracted from the ambient decibel level. Occupationalsafety standards (OSHA and EN norms) apply correction formulas to account for humanfactors and improper insertion margins in field conditions.
1. NRR Calculation (OSHA Correction Formula)
When ambient noise is measured in dBA, 7 dB is first subtracted from the NRR value (C–A weighting adjustment). A 50% safety margin (derating) is then applied to estimate actual fieldprotection:
Example: For a BBU Safety earplug with an NRR rating of 30 dB used in a 95 dBA noisyenvironment, the net noise exposure level for the employee is calculated as:
2. SNR Calculation (EN Standard Adjustment)
In the SNR system, noise attenuation is typically subtracted directly from the ambient noiselevel when measured in dBC. If the noise is measured in dBA, a safety margin of approximately 2 dB is deducted:
BBU Safety Quality and Safety Approach
All BBU Safety hearing protection products are certified by independent, internationallyaccredited testing institutions and comply fully with CE EN 352-2 standards. Selecting a BBU Safety product with the correct NRR and SNR values for field conditions is the mostvital step in preventing noise-induced hearing loss (NIHL).