From my previous blog (imagine my hubris thinking you read everything I write), you’ll remember that in 1994 Elliott Berger M.Sc., John Franks Ph.D. and Fredrik Lindgren Ph.D. showed us that real world attenuation is not the same as the rating a hearing protector gets in a laboratory. In fact, on average, real-world attenuation is significantly lower. In the search for best practices for hearing conservation programs, hearing conservationists were troubled by this fact. The unpredictable protectiveness (attenuation) from some forms of hearing protection needed to be quantified for them to know exactly what they were giving a particular associate. By some forms I’m referring to the “one size fits most” disposable protection that predominates the industry as well as the custom fit protectors. At this point, it is only fair that I point out that Custom Protect Ear’s position is that a significant cause of this condition (the variability of hearing protectors attenuation) is the variability of the ear and canal itself. Contributing to the problem of protective variability, of course, is the manner in which hearing protection is used. Just as a car won’t run well if the lug nuts on the wheels are tight, hearing protection must be correctly inserted if it is to have a chance of working properly. Some manufacturers think it is a training issue – train people better at inserting their hearing protection and it will work for them.
In this regard, several systems to aid in this training have been developed. These systems are currently being standardized in a new ANSI standard S12.71 now in development. At present their are 7 different systems all which report their results slightly differently. These systems need a common basis for comparing their results and the user needs to know how reliable their particular system is for them to use it effectively. These systems are called Field Attenuation Estimating Systems (FAES). Their purpose is to measure attenuation that a particular wearer gets after they have fit their protector. Then from training and practise they see if they can improve the attenuation thereby learning how best to wear their hearing protection. One the face of it this all sounds great.
At present there are seven different systems available. I’ll address 4 of them here because they are the most prevalent and are in the market today.
- 1. Fit Check – the grandaddy of these systems having been around since 1992, Fit Check replicates the Real Ear At Threshold (REAT) process used as the “Gold Standard” for hearing protection attenuation measurement. Instead of an anechoic chamber, Fit Check uses headphones, a control box, patient switch (for signalling) and a Laptop computer. It measures hearing with open ears and then again with occlude ears (with the earplug installed) and calculates an NRRsf (a personal attenuation rating) for that person and that protector. Fit Check takes about 2 minutes to learn and about 10 minutes to test and costs about $2,500 including a netback to run it on.
- 2. Ear Fit (Ear Fit is a trademark of the 3M company) – recently developed from the Sonomax Sonopass system, Ear Fit measures the insertion loss of a hearing protector installed in an ear by calculating the difference in sound pressure between an external microphones and an internal microphone in the earplug. To do this, Ear Fit uses “surrogate” earplugs with holes in them to simulate the earplug the user normal wears. The system computes this insertion loss and then adjusts the result for both using a surrogate and converting the result to an equivalent REAT measurement. At 5 minutes, Ear Fit is faster than most other systems and has the advantage that the wearer does nothing but provide their ears and insert the plug as they would normally do. There is no signalling when sounds are heard by the person being tested. The thinking is that through repeating the insertion process and measuring the results, the wearer learns how best to achieve the needed attenuation. It also allows wearers to choose plugs that best suit their ears eliminating those that just don’t work for their ear shape. Ear Fit costs about $3,200 + a laptop and only works with 3M hearing protectors which cost $1.67/pair for the surrogate protectors.
- 3. Veri-PRO (Veri-PRO is a trademark of Sperian/Howard Leight LLP) – Similar to the Fit Check system in that it uses a laptop and a headset, Vari-Pro is a loudness balancing system. The testing protocol is the person being tested puts the headphones on their ear and then moves a slider, via the touchpad until the sound they hear is the same in both ears. Then they put one earplug into their right ear and repeat the process balancing the sound until it is equal in both ears. Finally they insert the other earplug and repeat the process. From these actions the system calculates a result comparable to an REAT measurement. Veri-PRO can test any earplug that will fit under their headphones. Pricing for Veri-PRO runs $2,875 and includes the computer to run it on. Veri-PRO is only available through Sperian/Howard Leight distributors.
- 4. Well Fit – Well Fit is a trademark of NIOSH (National Institute of Occupational Safety and Health). Well Fit works similar to Fit Check and Veri-PRO in that it uses a Laptop computer and a pair of headphones. Well Fit is faster than Fit Check but works similar in that the person being tested indicates that the hear the sound but tapping on the touch pad of the computer. Testing using Well-Fit tkes less than 5 minutes and learning the system less than 2 minutes. Well Fit is currently being commercialized and NIOSH is working on arrangements to bring this system to market in the next 9 months. Current pricing for Well Fit system including the computer to run it, sound cased, headphones & software is $2,500.
You’ll note that all of these systems test only earplugs. At this writing, there is not a proven FAES for testing ear muffs.
There are two other systems worth mentioning.
5. Safety Meter by Phonak, the hearing aid giant, has a system which at this time only works with Phonak hearing protectors. That system works very much like the Ear-Fit system in that the wearer does not have to signal in any way. Testing takes 5 minutes and learning how to test 2 minutes. The system performs a MIRE measurement and reports the results with reference to REAT calculation techniques. Safety Meter costs $2,500 excluding the computer.
6. Quiet Dose by Sperian/Howard Leight is a different take on this problem. Quiet Dose does not measure attenuation; it measures the actual noise dose at the ear drum under the protectors. Quiet Dose is a personal dosimeter that associates wear all day. It records their daily noise dose for that work period. There is currently some research being done by Dr. Peter Rabinowitz at Alcoa sites on the efficacy of Quiet Dose. We’ll report on it when the study is made public. (By the way of full disclosure Custom Protect Ear made the ear pieces for the study Dr. Rabinowitz is conducting).
It seems that if you can test the attenuation of an earplug, and know that by testing it offers sufficient protection from a particular noise level, this will truly revolutionize hearing conservation programs. Right?
It seems all is not exactly that rosy. Alcoa has been using the Fit Check FAES system for fit testing and training in its facilities for 15 years. In fact, Fit Check, the first FAES, was developed because Alcoa was leading a charge to improve its hearing conservation programs. So if we are going to measure the efficacy of Fit Testing, Alcoa is where we should look. Dr. Peter Rabinowitz, a medical researcher with The Yale School of Medicine has studied Alcoa’s hearing conservation program extensively and published peer reviewed papers on his research. In Dr. Rabinowitz’s opinion “I am not aware of clear evidence of the effectiveness of fit testing in terms of improved hearing conservation outcomes“. Why?
Well one possibility is that what Fit Testing tells us is what the attenuation is for that person, using that earplug, at that moment. What is not yet proven is that over time, Fit Testing will result in changes to hearing conservation program outcomes. From his experience, Dr. Rabinowitz would certainly be among the world’s most experienced Fit Testing exponents. Also there has been no research published as to what the longer term effect of this new protocol will be. Does teaching someone how to properly fit a protector, for maximum attenuation make a difference? Why wouldn’t it?
Consider a situation wherein a trained associate comes to work and properly fits their earplugs. They then walk into noise and encounter another associate with whom they need to speak. What do they do? Since most earplugs, properly fit do exactly that, plug your ears, the speaker removes an earplug so they can make certain they are speaking loud enough to be heard over the noise (Elliot Berger taught me that in my first hearing conservation for beginners program at an NHCA Conference). The listener than removes and earplug to respond. If the noise level is just 95 dBA, and this happens for just 15 minutes a day, in those 15 minutes this associate has achieved 25% of their daily noise dose (using an action level of 85 dBA and a 3 dB exchange rate – if you would like this explained, respond to the blog and I’ll send you some info). Since the target for most associates is 50 – 60% of their daily noise dose at work per day, this associate should now work for 6 hours and then leave work. Part of the problem is then that earplugs, properly fit, tend to make the wearer functionally deaf. Communication frustrates protection.
Will FAES make a difference in hearing conservation program outcomes? I certainly hope so but I’m afraid much needs to be learned about the effect of these systems before we can announce to the world we have a way to beat Noise Induced Hearing Loss with FAES. So far, we need proof.