Welcome back to the Science of Safety Podcast. This time the podcast co-hosts Mark Reggers and Laurie Wells along with their guest, 3M’s Skye Liu, a Senior Specialist in China, to discuss the importance of fit for hearing protection. Fit and noise reduction are related and are key aspects of hearing protector selection and use. Tune in to learn more about fit for earplugs and earmuffs, fit testing methods, factors that can affect fit, best practices, and much more.
The first global season of the Science of Safety Podcast is presented by the 3M Personal Safety Division. This is a podcast that is curious about the science and systems behind workplace health and safety with a focus on personal protective equipment (or PPE) used to help keep workers healthy and safe.
This global podcast series will hope to not only give you another educational tool that you can use to help increase your knowledge but also something that you can share with others in your organization and with your friends. The goal is to help provide a global perspective and foundation for those of you new to workplace health and safety and personal protective equipment (PPE) while also providing information for more experienced professionals and complex health and safety challenges.
You can listen, subscribe to, and share this podcast through Apple Podcasts, Spotify, Google podcasts, Stitcher, and most major podcast apps and platforms.
If you have any questions or topic suggestions, you can get in contact with this podcast by contacting your local 3M office or visiting our worker health and safety website at 3M.com. If you’d like some assistance in your workplace when it comes to the appropriate selection, use, and maintenance of PPE please contact us today.
This year we are celebrating the 50-year anniversary of the first U.S. Government-approved 3M filtering facepiece respirator (a precursor to what is now known as the N95), and the 3M™ E-A-R™ Classic™ Earplug. To all of our customers who have trusted 3M brand PPE between then and now, thank you.
Around the world, we aim to help everyone get the job done safely today, tomorrow and in the future.
Below is the full transcript of the podcast:
Speaker 1:
The 3M Science of Safety Podcast is a free publication. The information presented in this podcast is general only, should not be relied upon to make specific decisions. Listening to this podcast does not certify proficiency and safety and health. You should always seek the advice of a licensed or certified professional in relation to your specific work or task. Always consult the user instructions for any personal protective equipment you are using and follow local laws and regulations. Information presented is current. As of the date of the podcast and requirements can change in the future. 3m owns all rights to the podcast and production is strictly prohibited without permission.
Laurie Wells:
Welcome back to our previous subscribers and welcome to our new listeners. The science of safety podcast is presented by the 3M personal safety division. This is a podcast that is curious about the science and systems behind workplace health and safety with a focus on personal protective equipment or PPE used to help keep workers healthy and safe. I am Laurie Wells, one of your co-hosts and I have the great pleasure to have Mark Reggers with me as well. We are occupational health and safety professionals who like to ask questions. Why, how, and please explain whether you are a safety professional, occupational, or industrial hygienist, someone with any level of worker health and safety responsibility in your workplace, a user of PPE or a health and safety nerd like us this is the podcast for you. Well, Mark, hello.
Mark Reggers:
Hello.
Laurie Wells:
I know that you have gotten to your favorite topic on our previous episode. And finally, today it is my turn.
Mark Reggers:
Yes, Laurie. I do acknowledge you have waited a very long time for it. And I know from your professional work, that our topic today hearing protective fit testing is near dear to your heart.
Laurie Wells:
So true Mark. Over my years of working in hearing conservation, and, um, by the way, I’m not saying how many of those years, right? I have witnessed a lot of changes, many advancements in technology, growth in the science and really some fundamental understandings that have changed our approach toward protecting people from hazardous noise. And when it comes to the workplace, I’ve seen the benefits of being able to measure just how much noise reduction a worker achieves from a particular hearing protector. It’s really fascinating science, and also just a ton of fun to see a person’s face light up when, when he or she understands how the hearing protector should be used in order to get the protection they need.
Mark Reggers:
Yeah, right. Then there is that important learning opportunity that is provided by the testing itself. You know, I mean, I can see a lot of similarities between respiratory protection and hearing protection with the most obvious being that every face and head and ear canal size is different. And the ability to assess the fit as it relates to protection achieved is key in knowing whether or not a worker is okay to be in these hazardous environments or not.
Laurie Wells:
Absolutely. And I’m so pleased Mark, that we are joined today by a very special guest, likely this person is our most experienced when it comes to conducting fit testing of hearing protectors, both from a practical application side in the workplace, but also in being able to conduct and publish her research. So please welcome our special guest Yufei Liu from 3M, China.
Skye Liu:
Hello, Laurie and Mark. It’s great to be here today. I’m so happy to be on the podcast also, please call me Skye. This is my more familiar name.
Mark Reggers:
Well, welcome Skye, it’s so fantastic to have you here with us today. Now, as Laurie said, you are well known for your field research on hearing protection fit testing. Would you please tell our listeners a little bit more about yourself and your role at 3M?
Skye Liu:
Yes. Thank you. I have been the 3M trainer in Personal Safety Division for more than 17 years, and I’ve specialized in regulations and standards. We have seen the need to have data about hearing protectors and how they are used by workers in order to support our standards development. So in the past few years, I have been dedicated to conducting fit testing studies that might help workers to improve their protection.
Laurie Wells:
Well, thank you Skye for joining us today. It’s really a treat. And, uh, I know you have a lot of experience and you could talk about this for a long time, but let’s just start with the basics. Would you please describe for our listeners what a hearing protector fit test is?
Skye Liu:
Oh yes. A hearing protector fit test measures the amount of noise in reduction that a worker achieves with a given fit of a given hearing protector. A typical fit test session goes like this. A worker is asked to fit the hearing protector as he or she typically does every day. Next, the operator makes the measurement of the noise reduction using special test equipment. The result of measurement is called a personal attenuation rating or PAR. The PAR is used then to determine if the attenuation achieved by that worker is enough to safely work in that noisy environment.
Mark Reggers:
So Skye, you make it sound way too simple. So maybe let’s break it down a little bit more. Now you said that there is special equipment for the measurement. So can you tell us a little bit more about that?
Skye Liu:
Sure. Yeah. Are actually several different ways that this noise reduction measurement can be made. We can separate them into two basic categories, subjective and objective measurement. And a subjective approach requires the workers to make a judgment and a response to a signal. An objective method uses equipment to make a physical measurement.
Mark Reggers:
So how does that apply to hearing protector attenuation measurements? And can you give us example if that’s okay?
Skye Liu:
Yes. One example of a subjective method is to determine a person’s hearing threshold. This measurement requires the worker to listen to a test signal and provide response. A typical test session is test the hearing threshold when there’s no hearing protector in place, the ears are open. Now, then ask the worker to wear the hearing protector. Repeat the threshold test, the ears are occluded. Now the hearing threshold will be elevated when a hearing protector is worn. So the difference of hearing threshold between the open and occluded ears indicates how much the hearing protector reduces the sound. This approach can be done as several frequencies of sound by repeating the above procedure. Then, these attenuation values at various frequencies are used to calculate the PAR.
Mark Reggers:
That seems pretty clear for subjective. A, listener indicates if the sound is audible or not. So how about for an objective method? How does that work?
Skye Liu:
An example of objective method is to use microphones to measure the sound pressure levels. A specific example is one microphone measures the sound pressure level on the outside of the ear. And another microphone measures the sound pressure level on the inside of the hearing protector at the same time. After a proper correction, the difference between the sound pressure levels on the inside and the outside of protector, tells how much the hearing protector is reducing the sound. This type of measurement does not require the workers to listen and response to a sound. It takes just a few seconds to complete the test and the microphones measures the sound at multiple frequencies at the same test. These attenuation values are then used to calculate PAR. At 3M, we have developed a fit test system that uses this objective measurement, also called field microphone in real ear that works together with the 3M hearing protectors, both earplugs and earmuffs. It’s known as the 3M E-A-Rfit system.
Laurie Wells:
Skye. That is great information with various methods available. It’s really good to understand something about the different approaches towards making the measurement itself, because certainly it affects the decision about which system to use. Unfortunately, we don’t really have a lot of time to explore all these different considerations when it comes to choosing a fit test system. But I know with your personal experience that you likely have something you could share with us, what is your experience in conducting fit testing and how does knowing that par help the, the worker?
Skye Liu:
Oh, I have so many stories to tell. I have tested thousands of workers in many different work environments in China. When workers learn that the attenuation is not enough for the noise environment and is greatly impacted by their fitting skills. The question on effectiveness of hearing protector is well explained. Workers will realize that they are playing an important role in protecting themselves. They will be convinced and motivated to learn how the hearing protector should be worn and how the protection increases with the improvement of the fitting skills. I have seen so many smiling faces when the good protection was finally achieved.
Mark Reggers:
I mean, from what you’ve explained, I can understand that the fit testing session has fantastic value when it comes to teaching workers about how the hearing protectors should feel and sound when it’s worn appropriately. But what about from the employer’s perspective? What does fit testing do for the employer?
Skye Liu:
Oh, there are many benefits to employer as well. The first thing that comes to my mind is that hearing protective fit testing allows employers to identify the workers who need attention. Multiple field studies have shown that a significant portion of workforce does not achieve the expected protection. In my study in China, nearly 4,000 workers from 16 factories were involved on average 49% of workers failed to achieve enough attenuation without the fit test information. The employers do not know who is at risk of insufficient protection.
Laurie Wells:
Wow, that’s quite significant. 49% of the workers failed to achieve enough attenuation. So that’s quite a surprise to the employers. It’s really important Skye because one of the key components to driving a successful preventive program is to be able to identify who is at risk early enough, that you can actually provide an effective intervention. So most hearing conservation programs include routine hearing tests, but it typically takes a long time before a hearing loss from noise exposure will show a significant change in the hearing thresholds with hearing protector fit testing. We now have a tool that allows the employer to identify that population of workers who are at risk of being overexposed when they can’t achieve the sufficient attenuation. So it’s really a proactive approach to intervention.
Mark Reggers:
I’m sure there are other benefits too, like being able to document that a worker has been trained and is actually able to achieve the appropriate attenuation needed for that job or for that task. Uh, what other benefits are there Skye?
Skye Liu:
Another aspect is that you can really have to manage the types or hearing protectors that are needed to fit everyone in the workplace. While there are hearing protectors that work for most people, there isn’t one that fits every person and every ear. It’s a benefit to have the fit testing results, to know which hearing protector needs to be retained. And also, if there are unique cases where a certain hearing protector is needed for a certain person or even work environment.
Laurie Wells:
Well, something we haven’t yet talked specifically about yet Skye is how does the employer know or decide if the attenuation is appropriate or not? Could you speak to that?
Skye Liu:
Sure. This is pretty straight forward. The employer needs to set the target for noise exposure when hearing protectors are worn. Often that depends on the regulatory limits for noise exposure, but sometimes the employer decides to set a limit that is lower than the legal limit, just as an additional safety factor.
Laurie Wells:
Oh sure. Of course, like in the US, the permissible exposure limit is 90 decibels on the A scale time weighted average. And the action level is 85 dBA time weighted average. So many employers would choose the action level or sometimes even lower such as 82 or, or maybe even 80 dB to ensure that extra safety factor.
Skye Liu:
Yes. Good example. Once the employer sets the target, then it is a simple math. Take the noise exposure level that is measured on A scale and subtract PAR. For instance, let’s say the target is 80 dBA. The noise exposure for a mechanic is 91 dBA and the PAR is 16 DB, then simple math 91 minus 16 equals to 75 dBA. The protected exposure is less than the target. So this example shows adequate protection.
Mark Reggers:
Okay. I love that the math is simple cause I am a simple man, but how about a PAR of six or four? Is that possible?
Skye Liu:
Yes, it’s possible. There is a valid range of PAR values and that information should be made available by the manufacturer of the fit test system. Let’s say if that mechanic gets a PAR of 4 dB, then 91 minus four equals to 87, that is not enough to reach the target. So now there is opportunity to observe how the worker is wearing the hearing protector and coach him if needed. Repeat the test to verify if the person can get a higher PAR, If yes, then reinforce the lesson and document the results. This can be repeated until the goal is met. In some cases, a different hearing protector style or model may be needed to reach the attenuation goal.
Laurie Wells:
Yeah. And another advantage of individual fit testing is that often times a person has a difference in fitting the right ear than the left ear. And now we have a tool that we can show. If one ear is a, a so-called troublemaker. I know for taking myself as an example, my left ear is much more difficult to fit than my right ear. It takes me a bit more time and attention to, to get that seated just the way I need it to get the attenuation. And what’s really nice is that the ear fit system gives ear specific, but also a combination of binaural PAR value. And this can be very helpful for identifying people who need extra help in coaching and also in helping to focus in on the training.
Mark Reggers:
So Skye, it sounds like you have had a lot of experience with hearing protective fit testing. Is it difficult to learn how to conduct the tests? Is there some kind of certification required to be a hearing protective fit tester?
Skye Liu:
Well, there’s no requirement for certification to do fit testing. Actually conducting the test is not so challenging. The true skill is on coaching a worker and troubleshooting a difficult hearing protective fit. Most of my experience is using the 3M EARfit system, and I have seen that when trainers use the objective data from EARfit, it helps them to improve their training. They learn from seeing the results. If the first fit isn’t suitable, try another fit, run the test, see the results. Also, if the worker can see how the hearing protector fits and see the value of PAR on the screen.
Laurie Wells:
Well, speaking about certification brings to my mind at the regulatory aspect of hearing protector fit testing. And I just like to mention that there is no country right now that requires hearing protector fit testing. However, there are many countries that recognize the value and the benefits of fit testing to both the employees and the employers and are recommending it as a best practice. Now, Skye you’ve conducted a lot of studies and published journal articles on your findings. And I thought it might be a nice way to close our session today by having you share what you believe to be the most valuable lesson learned, or perhaps you could speculate on how fit testing might impact the hearing conservation program in the future.
Skye Liu:
Yes. In our studies, the following benefits of hearing protective fit testing has been proven: helps to identify workers at risk of insufficient protection, assist in proper hearing protective selection, and it is an effective training tool. More over conducting fit testing, enhanced their communication with workers. It’s a great chance to motivate workers, to use hearing protectors correctly and help them to remove the barriers of using hearing protectors. I believe the fit testing not only provides scientific PAR values. It is also a practical tool that can help improve the outcomes of hearing conservation programs. Eventually can help reduce cases of noise induced hearing loss in, in the long run.
Mark Reggers:
That’s so terrific Skye. I can feel your passion, even as I sit here in Australia and you in China. Now for our listeners, 3M has many helpful resources regarding hearing protective fit testing, like tech documents, fit test eBooks, videos, and of course this very podcast episode. Now you can visit 3m.com/earfit for more information.
Laurie Wells:
Well, Skye it’s been an absolute delight to have you share your insights and your experience with us. It’s always nice to connect. Uh, especially now we have the US and China and Australia together at one time. It’s just wonderful. So thank you so much for taking the time today to chat with us.
Skye Liu:
It’s been fun. Thank you for inviting me, Laurie and Mark. I’m always happy to share my stories.
Mark Reggers:
I know we’ve only just touched the tip of the iceberg of your knowledge Skye, but perhaps maybe we can have you come back next season to share a bit more. I mean, it really is helpful to talk with someone who has both the technical knowledge and the practical experience, uh, with workers. Well, thanks for listening everyone. You can listen, subscribe to and share this podcast through apple podcast, Spotify, Google podcast, and most major podcast apps and platforms. If you have any questions, topic suggestions, or like some assistance in your workplace, when it comes to the appropriate selection use and maintenance of PPE, you can get in contact with this podcast by contacting your local 3m office or visiting our website mmm.com. This year, we are celebrating the 50 year anniversary of the first NIOSH-approved 3M filtering face piece respirator and the 3M E-A-R Classic Ear Plug. To all of our customers who have trusted 3M branded PPE between then and now we thank you. Around the world we aim to help everyone get the job done safely today, tomorrow, and in the future. Thanks for listening and have a safe day. Stay healthy, Laurie.
Laurie Wells:
Stay safe and sound Mark.
Mark Reggers:
Thanks everyone. Bye.
Laurie Wells:
Bye. Bye.