by Capt Tressie Waldo
Brooks AFB, TX
How do you determine if a worker’s hearing protection is effective? I’m sure you all check the fit of the hearing protective device (HPD) and ensure the worker is using the appropriate insertion technique. Are you also calculating the at-the-ear exposure level? According to OSHA, when a worker has a STS, the effectiveness of the HPD must be calculated to ensure the at-the-ear time-weighted average (TWA) is no more than 85 dB. Furthermore, HSI inspectors expect to see these calculations in the medical records of all patients with STSs. Now that does not mean that the HCDC/HCC audiologist has to do the calculations. However, I have found that most units are not calculating HPD effectiveness, so it comes down to us, the audiologists, to ensure it gets done.
So, how do you determine HPD effectiveness? It’s very easy to do if you have all the data. You need to know the particular HPD, the NRR of that HPD, and the worker/shop TWA. The problem comes with the TWA. At HCDC locations where all you get is the medical record, you will have to search for the TWA. If the worker has exposures other than noise, an AF Form 2755, will be in the medical record and will have the TWA listed. Workers exposed only to noise will not have the AF Form 2755 in the record. If the HCDC is expected to calculate HPD effectiveness, then the unit must supply the TWA on the AF Form 1672.
Now that you have all the data, you can plug the numbers into an equation. OSHA recommends several ways to do this. NIOSH also has several methods for calculating it. The easiest method is: TWA – (NRR – 7). I recommend using the NRR obtained at Wright-Patterson stated on the Approved HPD listing. The TWA should be the A-weighted TWA. If the number is under 85 dB, the HPD is effective.
You may be asking yourself, why do I have to write out a mathematical equation in the medical record. I can speak personally that the HSI team expects to see calculations in individual medical records. LtCol Linda Rollins was one of my inspectors at Kelly AFB, and she was pleasantly surprised to see we were doing it right. She had seen many cases of people documenting that the protection was adequate, but were not showing how they had determined that. She wanted to see the process itself.
The best way to ensure the HPD effectiveness calculation takes place is for the unit to do it. Whenever a patient shows a STS an annual audio, they should be referred to Public Health for education and refit of HPDs anyway. Perhaps you can convince them to do the calculations also. They could add a few lines to their SF 600 overprints so all they have to do is fill in blanks or circle items. Something like this would be sufficient:
S: Type HPD used: ____ V51R ____ Triple Flange ____ EAR ____ Muffs ____ Comm headsets ____ Other O: HPD effectiveness: TWA dBA - (NRR - 7) _____ - (____ - 7) under 85 dBA? ___yes ___no A: HPD effective? ___yes ___no P: Change HPD to: ____dual protection ___wear HPD correctly P: Wear HPD around all noise, occupational and recreational.
There are other, perhaps more effective, methods for calculating HPD effectiveness. However, they are usually more time consuming and require more data than may be readily available. Neither OSHA nor the HSI states who is responsible for the calculation. It just has to get done. As you can see, it’s an easy process. Why not meet OSHA guidelines and score a few brownie points with the HSI? If you would like more information on this or alternate methods, please call me or send me an e-mail.