Monthly Archives: February 2014

Alternative to Relying on the NRR

February 25, 2014

Measurement of Insert-type Hearing Protector Attenuation on the End-user: A Practical Alternative to Relying on the NRR

NRR Data

Hearing protectors are labeled with a Noise Reduction Rating (NRR) that is derived from laboratory measurements of the attenuation provided to trained and motivated human subjects in a ‘sterile’ environment. As intended, these measurements represent a best-fit condition. The literature indicates that the average attenuation provided to end-users of hearing protectors is often only a fraction of the labeled values. Because of this, various derating schemes are employed, including the 50% derating suggested in the OSHA inspector’s Technical Manual and the variable derating according to protector-type suggested in the 1998 NIOSH criteria document on occupational noise exposure.

De-rating the labeled NRR

De-rating the labeled NRR provides a better estimate of the average attenuation realized by a population of end-users. However, field measurements indicate that attenuation provided across end-users is highly variable (standard deviation > 10 dB), so many wearers will receive much greater attenuation than the average, and many will receive much less attenuation than the average. Therefore, if hearing protectors are selected according to a de-rated NRR, some individuals will still be under-protected and some will receive excessive attenuation, leading to potential communication problems. A solution to this problem is to base the selection process on objective data obtained by measuring the attenuation provided to each end-user of insert-type hearing protectors.

dB Blocker

In this article the Steel Industry experience is examined when it comes to individual hearing protector fit-testing.  In this industry Almost all HPD wearers at this plant wear insert-type devices. To learn more about the wide variability of attenuation provided by insert-type protectors a results please click here to download the entire study: DOWNLOAD PDF 

 

 

Field Attenuation Estimation Systems: THE POSSIBILITIES

February 11, 2014

Noise Reduction Rating (NRR)

Hearing protectors are labeled with a Noise Reduction Rating (NRR) that is derived from  laboratory measurements of the attenuation provided to trained and motivated human subjects in a ‘sterile’ environment. As intended, these measurements represent a best-fit condition. The literature indicates that the average attenuation provided to end-users of hearing protectors is often only a fraction of the labeled values. To learn more about the practical alternative to relying on the NRR, click here. 

Custom Protect Ear would like to present a FREE  WHITEPAPER about obtaining Personal Attenuation Rating (PAR) that is compared to Noise Reduction Rating (NRR).

Field Attenuation Estimation Systems: THE POSSIBILITIES

Would it be nice if you could determine how effective a hearing protector was under workplace conditions. In Appendix FAES The PossibilitiesIV:C of the OSHA Field Manual, Methods for Estimating HPD Attenuation, U.S. OSHA states, “The actual effectiveness of any individual hearing protector cannot be determined under workplace conditions” (U.S.Department of Labor). This has never been completely true. It has been difficult, but not impossible, to determine the actual effectiveness of any individual hearing protector for any individual user because of two issues. First, there has been no available commercial product for testing hearing protector effectiveness for the individual user until just recently – for less than 10 years compared to an OSHA regulation on noise and hearing conservation that dates back almost 45 years in its most skeletal form. Second, there have been no accessible commercial methods for determining the effectiveness of any individual hearing protector for any individual until recently. In fact, now there are three:

  • There are methods involving simulations of the real-ear attenuation at threshold (REAT) using large-cupped earphones to place over the ears to test earplugs. (Michael and Associates FitCheck, Workplace INTEGRA, Inc. INTEGRAfit, NIOSH Well-Fit and FitCheck Solo)
  • There are methods involving having a person balance the loudness of a signal presented to an open ear to that of a signal presented to an ear occluded with an earplug.
  • There are methods that employ the use of a sub-miniature or probe microphone placed in a surrogate protector to predict what attenuation a user would receive when wearing the actual hearing protector in a similar manner.

To read complete paper fill out the form to get the Field Attenuation Estimating System Whitepaper Report. Click here: