Protection Requirements:
- Noise Reduction:
- Environmental noise must be reduced to below 85 dB to protect hearing from noise-induced damage.
- Appropriate hearing protection equipment should be selected based on the noise level.
- Communication Needs:
- While reducing noise, hearing protection should allow for basic communication and awareness of environmental changes.
- In situations where users need to communicate with each other, hearing protection equipment with an NRR*23 rating should be selected. This ensures that noise is reduced below 86 dB while maintaining a sound level above 70 dB so that speech remains intelligible.
- Detectability in Special Environments:
- In certain industries (e.g., the food industry), it is strictly prohibited for earplugs or other foreign objects to mix into the final product. Therefore, earplugs should have detectable properties.
*NRR 23 (Noise Reduction Rating):
Noise Reduction Rating (NRR) is a statistical conclusion derived from a sample population, reflecting the subjective noise reduction experience of each individual. However, it does not represent the actual noise reduction effect for every user. The noise exposure level after wearing hearing protection varies based on selection, fit, and effectiveness, meaning it cannot be simply calculated through subtraction.
However, according to relevant regulations, a reasonable estimation can be made to help choose suitable hearing protection:
- OSHA Regulation: The actual noise reduction achieved after wearing hearing protection is estimated to be half of the device’s rated NRR value.
- NIOSH Regulation: The actual noise reduction varies by product type:
- Earmuffs: ¾ of the rated NRR value
- Foam earplugs: ½ of the rated NRR value
- Other types of hearing protection: 30% of the rated NRR value
Selecting the Right Hearing Protection:
Users should choose appropriate hearing protection based on their specific needs and ensure proper wearing techniques to maintain noise exposure levels between 70 dB and 85 dB.
NRR is the most commonly used rating method, but it is not the only one. Another classification system is the Single Number Rating (SNR). Due to differences in standard systems and testing methods, SNR values are generally higher than NRR values for the same hearing protection device.
