Welcome to today's webinar series, Train the Trainer. My name is Kristen Wadsworth. I am a board-certified hearing instrument specialist. I'm employed by HearUSA as part of their learning and development management team. I also serve on the International Hearing Society's Institute Committee, which focuses on general education for hearing instrument specialists and for the field of audiology. A special thank you to Sierra Sharp and IHS for having me here today. And also a thank you to my partner on this project, Rebecca Krause. Today's webinar series topic as part of the Train the Trainer series is masking made easy. Masking is one of the most fundamentally important concepts in our industry and often one of the most challenging to teach. Masking is a passion of mine, one of my favorite subjects to teach because there is nothing more rewarding than watching masking click for an apprentice. The purpose of today's training is, of course, to provide our fellow sponsors and mentors with a strategic plan and necessary tools to teach effective masking. I'm happy to be working with each of you today and hope that you find this training to be beneficial. Let's make masking easy. A few general housekeeping announcements before we start today's webinar series presentation. This session will be recorded. One CEU credit will be available by visiting ihsinfo.org for further details. The slides will also be available to download at education.ihsinfo.org on the webinar page. And there will be an additional masking guide or key provided to supplement today's learning and serve as an additional tool for clinical usage. In our agenda for today, we will first cover some of the theoretical framework surrounding why masking is necessary, identifying the concepts that must be understood for successful practical application of masking. We will then bridge our learning to the practical application of masking where we will first cover and identify using IHS testing protocols. When masking is necessary, getting set up properly, what procedures are used, what calculations and values must be applied to achieve effective masking. Masking theory. For a clinician to successfully complete the procedure of masking in the clinical setting, they must first understand the purpose of masking and the supporting important concepts that are associated with masking. It is important for the trainer to provide a real life situation as an example to prepare the apprentice to understand the basic concepts of masking. The classic example of masking that occurs in everyday listening situations is when a client is speaking with their spouse in the kitchen and their spouse turns on the sink and starts the process of washing the dishes. The combined noise of the running water as well as the clamoring of the dishes disrupts the client from being able to effectively communicate with their partner. The running water and clamoring of the dishes mask the conversation that is trying to be exchanged. Important terminology that we will be discussing today include the following, interaural attenuation, cross-hearing, crossover, mirror audiogram, under-masking, over-masking, effective masking, occlusion effect, and the plateau method. Purpose of masking. Clinical masking must be completed to measure auditory function accurately. If masking is required for a given client and not for a given client, the negative effects of this oversight can result in inaccurate testing and inappropriate recommendations. Situations will occur during pure tone testing that will require the tester to ensure that the ear being tested is truly the ear responding to the test signal. Masking is a procedure that is used to eliminate any participation of the non-test ear during threshold determination of the test ear. The successful completion of clinical masking will be determined by the test result. The failure of clinical masking will result in accurate client threshold determination, resulting in increased testing accuracy and recommendations. The concepts of interaural attenuation and crossover are the reason masking may be necessary to measure auditory function accurately. Interaural attenuation. Interaural attenuation represents the loss of sound as it travels from the test ear across to the non-test ear. Interaural attenuation can occur by way of air conduction and bone conduction, though we tend to focus more on interaural attenuation via bone conduction. It's easier for bone conduction information to travel via vibration through the skull by vibrating the other cochlea than it is for sound to travel from one side of the head via air conduction around to the other side of the head to the other ear. Both cochleas are typically stimulated at the same time when a stimulus is being presented. So interaural attenuation for bone is said to be felt at even as little of as zero decibels. So quite literally it takes practically nothing for the other ear to be stimulated during testing for bone conduction. Crossover and cross-hearing. Cross-hearing occurs when the stimulus being presented to the test ear occurs at such a high intensity level that it actually exceeds interaural attenuation. And we will identify the interaural attenuation values later in today's presentation. Crossover occurs as a result or really when sound being presented to the test ear travels across the head to the non-test ear. So think of that more as the outcome. This occurrence gives rise to false positive results, further reinforcing the need for clinical masking. And there's a great diagram here on how that is occurring. Three concepts or three different types of masking. The three different types of masking include under-masking, over-masking, and effective masking. Effective masking is the goal or desired outcome of clinical masking procedures. When a clinician is under-masking, what that means is too little masking is being applied to the non-test ear and crossover may still occur. If a clinician is over-masking, too much masking stimulus is being applied, which will shift the test ear response, making it inaccurate. Over-masking can cross through the test ear and also negatively impact the test ear results by masking the test ear as well as the non-test ear. Effective masking will occur when a clinician is applying just enough or just the right amount of masking to prevent crossover from occurring and will not impact the test ear threshold. Effective masking is the goal or desired outcome of clinical masking. The plateau method. The plateau method is an important component of the procedure to complete clinical masking. The plateau is a state in which the non-test ear is completely masked by noise and the tone is only heard by the test ear, of course, if completed appropriately. We are striving for a plateau method of 15 decibels during clinical masking. The goal of the plateau method is that the test threshold remains stable when the masking noise presented in the non-test ear is increased five decibels three consecutive times without shift of the test ear threshold. Appropriately, we will reach plateau in the test ear response. Additional considerations that can negatively impact the success of the plateau method are air conduction thresholds in the non-test ear, interaural attenuation variability, transducer type, and occlusion effect magnitude. Mirror audiogram or shadow curve. Mirror audiogram is also referred to as a shadow curve and can be indicative that the procedure of masking is necessary. Much like when we discuss and understand configurations in audiometric interpretation, how we can understand the mirror audiogram is by visualizing the shape or pattern that the air conduction thresholds take. In this particular audiogram, the better ear being the right ear and the poor ear is the left ear. The configuration of the left ear very closely mimics the configuration of the right ear in terms of shape or audiometric pattern. What this tells us is that the better ear is helping the poor ear. By completing masking by way of air conduction, we will obtain independent and accurate thresholds for the left ear. Occlusion effect. The occlusion effect is an important concept when understanding and completing masking procedures for bone conduction. This is an acoustic phenomenon that we account for when testing as part of our calculations for masking for bone conduction procedures specifically. What is actually occurring is low sound is being transmitted intercranially, which may increase or improve the bone conduction threshold because it is being blocked by the transducer and will create additional occlusion effect beyond what is naturally occurring. By accounting for this variable, we are trying to overcome the occlusion effect, which occurs in the cartilaginous portion of the ear canal. The formulas that we are going to implement and discuss today account for the occlusion effect variable. The occlusion effect has more significant impact on the lower frequencies that are being tested, which you will notice as our higher frequency occlusion of variable effect decreases. Supporting tools. Now that we have covered the theoretical concepts of masking as well as the necessary concepts and terminology of clinical masking, we can now move on to teaching the process of clinical masking. Let's discuss our supporting tools for today's presentation. Masking chart. When teaching masking, the first and foremost, you know, often reported challenge is not knowing where to start and what information to use. This chart is designed to walk you, your student or apprentice, step-by-step through the masking procedure and will also serve to consolidate all the necessary information into one place. This is a great tool for your apprentice and student to utilize when referencing masking protocols and completing the procedure of clinical masking. The chart is meant to be read and followed from left to right. The first column identifying whether the individual is testing for air, bone, or speech testing. The second column representing the rules of when to determine if masking is necessary. The third column providing the formulas that must be applied. In the fourth and final column, knowing what procedures to complete to reach effective masking. Please note that this chart utilizes IHS testing protocols for masking and IHS testing values. While we understand and appreciate that there are other methodologies and approaches for completing and reaching effective masking, we ask that you utilize these values when preparing your apprentices and students for their international licensing exam, both written and practical. IHS masking procedures. Let's now discuss IHS's approach to completing effective masking. In today's session, we've already covered how we can approach and discuss some of the key concepts as to why masking is necessary. Once the student is able to understand the theory behind masking, we believe that they will then be able to better apply the procedure of clinical masking. The next step in this process to break down the clinical application of masking is knowing why masking is necessary, which we will touch upon in a few moments. But first, there are just two pieces of getting set up properly that I would like to discuss with you. The first of which is understanding and being able to differentiate between test year and non-test year. This is incredibly important. A quick and easy mnemonic device is to isolate the terminology associated with T, so T, tone, test year, true threshold, and N, noise, narrow band, non-test year. To determine knowing when masking is necessary, the apprentices first must be able to distinguish test year from non-test year and contralateral versus ipsilateral. An easy way to simplify this concept and to teach it is to draw a client's head on a whiteboard, ask them which year is the test year and non-test year, and have them label this accordingly, and also having them place the appropriate transducer. My approach to this was to purchase a large fat head, a cardboard life-size picture of a human head, a client's, and essentially the apprentices, excuse me, had to take the transducer and place the transducer on that fat head. So essentially like pin the tail on the donkey, audiology style. But essentially, really help the students to first understand and be able to differentiate test year from non-test year, and also focus on whether that be air or bone conduction masking, which one was occurring based on what it was that we were interpreting. You can try to make this area of understanding masking fun and giving the apprentices the opportunity to have some practice before they go ahead and start with the actual process on a live client. This is a way that we can work with our apprentices, our students to make masking fun. Next piece of the setup is to discuss contralateral versus ipsilateral comparison. In order for a student to be able to separate whether it is bone conduction or air conduction that is necessary, they must be able to distinguish these two terms. The rule of masking for air is a contralateral comparison, meaning we are comparing air conduction testing of the poor ear to air conduction and also bone conduction of the better ear. To put simply, we are comparing information from opposite ears. The rule of bone conduction on the other hand is ipsilateral, meaning the comparison occurs between the air conduction threshold of the test ear and the bone conduction threshold of that same ear. To put simply, we are comparing the same side to itself. I always tell my students to ignore the non-test ear for the moment when we are trying to isolate and determine if masking is necessary for the test ear when we are focusing on bone, comparing that same side to itself. So far, we have discussed knowing why masking is necessary and also have provided a few tidbits for first getting started and getting set up appropriately. Let's now look into knowing when masking is in fact necessary. The first piece to analyze referring to our masking graph is knowing when masking is necessary for air conduction. You will mask for air conduction if and when there is a difference between the threshold of the poor ear and the better ear that exceeds interaural attenuation. This will vary based on the testing transducer that is being utilized during testing. If you are utilizing insert earphones, the interaural attenuation value is 70 decibels. If you are using headphones, the interaural attenuation value is 40 decibels. This is the first rule of when to apply masking for air conduction. The second rule or comparison that needs to be made to determine if masking for air conduction is necessary occurs when there is a difference that exceeds interaural attenuation between the poor air conduction threshold and the better bone conduction threshold of the better ear, if that as well exceeds interaural attenuation. The interaural attenuation values remain the same for the second rule of masking for air conduction. It is very important to know the key for success of interpretation and implementation is testing in the recommended sequence. Can't emphasize this enough. This is often where a lot of the confusion comes into play with the second rule of when masking for air conduction is necessary. We suggest that the apprentices test in the following sequence, air for the poor ear, air for the better ear, bone for the poor ear, bone for the better ear. I strongly suggest when mastering this component that you collect or create audiograms where masking may be necessary, but not fully completed. And first have your apprentices practice this key piece of interpretation. It is again, a contralateral comparison, meaning that we are comparing information from opposite ears. Now moving on to knowing when masking is necessary for bone conduction. So we are now moving down our graph and looking at the column of bone conduction still remaining in the first column, row two. Masking for bone conduction is necessary when there is a 15 decibel or greater difference between the air conduction threshold and the bone conduction threshold of the test ear or same ear. It is again, an ipsilateral comparison, meaning we are comparing the same ear to itself. When to mask for SRT. Speech recognition threshold. Masking is necessary when the difference between the unmasked SRT of the test ear and the best bone conduction threshold of the non-test ear exceeds interaural attenuation at either 500, 1000, 2000, or 4000 hertz. It is important to know the interaural attenuation values for speech testing is different from that of air conduction testing. It is 60 decibels using insert earphones. The interaural attenuation value for headphones will remain 40 decibels. So please note the difference if utilizing insert earphones. Following the same principle made earlier, it is crucial that we first have the information necessary for comparison before we can complete these procedures. We must first test for air and then bone and then we can move on to speech testing. We must first complete unmasked SRT testing for both the test ear and the non-test ear before we can determine if masking is in fact necessary for the poor ear. We will then have to repeat the SRT procedure after we have applied the appropriate amount of masking to the non-test ear. When to mask for word recognition. Masking is necessary for word recognition when the difference between the presentation level or rather the intensity level used to complete word recognition testing and the test ear unmasked and the best bone conduction threshold of the non-test ear at either 500, 1,000, 2,000, or 4,000 exceeds interaural attenuation values. Again, reminder that for speech testing, our interaural attenuation values, specifically when using insert earphones, is slightly different at 60 decibels. Now let's move on to some discussion of practice and what this should look like in the clinical setting. Again, as mentioned earlier, we highly recommend first teaching an apprentice when determined if masking is necessary for air conduction. This is a great strategy and a great opportunity for us to create some audiograms to reference if and when masking is necessary but not yet completed or not yet completed in its entirety. We recommend first starting with air conduction, then progressing to bone conduction, and then obviously progressing on to speech testing. In this example, we'll guide our apprentices first to determine which ear is the test ear, then the non-test ear, and let's move on to that audiogram for reference. The first thing that I ask my apprentices when evaluating an audiogram like this is what information has been provided, and based on the information provided, what can we determine is necessary and what can we not determine may be necessary? So this example here, obviously having the apprentice identify that air conduction has been completed for both sides and really determining that masking would be necessary for air conduction because that is the only information that we have provided, checking off that box for rule one of air conduction testing to know that masking is necessary. And of course, being able to reference both transducers that can be utilized, this would be necessary for headphones because we can see we have a few frequencies here where there is a clear 40 decibel interaural attenuation value. But if we were to have utilized our insert earphones, then we likely would have not needed to mask for air conduction for this audiogram. But of course, we cannot interpret rule two of air conduction masking because we don't have our better bone information, and we don't have our bone conduction information for the left side, so we cannot determine if masking is necessary for either ear on its own independently. For the next audiogram, we can follow and analyze and determine if masking is necessary for bone conduction. Taking a step back for a moment, I always, again, like to ask the apprentice what information has been provided. And in this case, let's start with the left ear as the test ear. At any point, the frequencies provided, is there a 15 decibel or greater difference? And obviously, we can see here clearly for the left side, there is a 15 decibel or greater difference at 500 and 1,000 hertz. So we would isolate the left side, and we would follow through with the steps necessary to complete effective masking. I do recommend not only using audiograms like this as examples of knowing when masking is necessary, though that's naturally where you will start. I often, too, will have the apprentice take me through their entire process. So first, knowing when masking is necessary, then determining which calculation is appropriate, including the occlusion effect variable, which we'll discuss in a moment, and then following the procedure that will be necessary to complete masking. And of course, on the right-hand side here, we have also provided our unmasked speech testing information for both SRT and word recognition. So following the same model for talking through and working through practice examples of when masking for speech testing is also necessary, an audiogram like this would be a perfect example of that. So, so far, we have covered knowing why masking is necessary, touching on a few points for getting set up with success, knowing when masking is necessary. So being able to look at an audiogram and visually interpret those into oral attenuation differences, how those are being demonstrated on the audiogram. What I'd like to move on to now is applying the proper formulas, knowing how much initial noise to deliver to the non-test ear. Now let's move on to formulas that must be applied to complete clinical masking. I always encourage my apprentices to memorize these formulas as the first step to mastering masking, even if they don't yet understand its application. Implementing the procedure air conduction, initial masking level. Once the correct formula is chosen and the initial masking level is applied to the non-test ear, the apprentice will then shift their focus to the test ear and begin to complete the process itself. We first want to take a step back and say to the apprentice, okay, when you have determined that masking is necessary for air conduction, how much initial noise do we need to put in the non-test ear? We will have the apprentice recite the formula air conduction of the non-test ear plus that 10 decibels, okay? So we will look at the audiogram, interpret what that threshold is for that frequency of the opposite ear, add 10 decibels to that, and that is how much initial masking noise we will introduce to the non-test ear. Then we can proceed to the component of focusing and shifting our attention back to the test ear to first bracket, to reestablish thresholds, and then we can go shift our focus to the non-test ear and embark in the plateau method so we can reach effective masking. Initial masking level for bone conduction. If the provider must apply masking for bone conduction, the formula that they will utilize is the air conduction threshold of the non-test ear plus 10 plus the occlusion effect variable. The occlusion effect variable is accounted for is accounted for or calculated, estimated by frequency. So at 250 hertz, we would add 15. At 500 hertz, you would also add 15 along with 750 hertz, but at 1,000, you would change that occlusion effect variable to 10, and for 1,500, 2,000, 3,000, and 4,000 hertz, that value would be zero. When a provider will need to apply masking for SRT testing, the formula that will then be accounted for and utilized is the SRT of the non-test ear plus 10. Again, friendly reminder, I can't emphasize enough the importance of not only completing speech masking, but also completing the test in the recommended sequence. So by first testing air, then transitioning to bone conduction, then transitioning to speech recognition thresholds, first testing each ear, better ear, and poor ear, then being able to determine if masking is in fact necessary for speech testing as well. Initial masking level for word recognition. I'm sure some of you have noted between last year's edition of the coursework as compared to this year's edition, the method or the formula for masking for word recognition has changed slightly. As previous, MCL minus 20 dB was utilized. Now, we are using the 2 kilohertz method for the test ear, and we are subtracting 20 from that value. Below, for those of you that are unfamiliar with the 2 kilohertz method, we have given you those calculations there. So for example, and again, this is simply just the presentation level that we utilized to complete word recognition testing of the test ear in the unmasked condition. So for those of you that are unfamiliar, I think it would be productive to give an example. So let's say we're looking at the left ear, and the threshold for the left ear at 2,000 hertz is 25 decibels. We know per the first category that threshold is less than 50 decibels HL, so what we would do is we would present the words at 25 dB SL. So simply, if the threshold was 25, we would add 25 to that, and so we would use 50 decibels for our presentation level for word recognition testing for that ear. Following that same methodology, looking at our initial masking level, we would put 50 and insert that into the first component of the calculation. So 20 from 50 is 30, and that would be how much masking noise we would simply apply to the non-test ear. Once the apprentice has clearly mastered identifying when masking is necessary, proper placement of the transducer and setup, and as well as understanding the proper formulas to apply for initial masking level, we can now move on to understand procedures that are necessary to reach effective masking. I like to break down the procedure into three steps for simplicity. Step one, applying the correct formula for the non-test ear masking noise presentation level. So essentially, to put simply, how much initial noise to introduce to the non-test ear to start the process. Then shifting our focus back to the test ear, focusing on that test ear so we can reach a true threshold, we first want to do our bracketing or ascending-descending method. One time, our simple down 10, up 5 to reestablish that threshold, and it is best practices to complete that full bracketing. So two out of three attempts where the client responds at least 50% of the time. Once we have successfully reestablished that threshold with the initial masking noise being presented to the non-test ear, we then need to complete the plateau method, which we have discussed earlier is 15 decibels. So essentially what the apprentice is doing is they are increasing the masking noise three consecutive times in intervals of five decibels without shifting the threshold of the test ear, really confirming that we are not over-masking and that we are not under-masking as well. So on the right-hand side of the masking chart, we have just very simply stated bracketing method and then of course the plateau method, and this would apply for both ear and bone conduction testing. As far as navigating challenges is concerned, we've already mentioned this earlier, but I think it is important to identify this again. It is crucial for the mentor, for the sponsor to adopt IHS masking protocols, starting by first of course acknowledging that there are different methods to achieve effective masking. Simply put, the way that I would communicate this to my apprentice, having learned how to complete masking using a different method, what I am teaching you is not the only way to conduct masking. In fact, when I was learning masking, I was taught a completely different procedure. So again, I encourage you to teach your apprentices the ways in which you've utilized masking, but err on the side of caution that that might be confusing to them because that is different from what they are reading, that is different from what they are studying in the coursework, and I think that will have its place later in the process once they first truly understood the theory of masking, and then to IHS's approach to completing masking. What I also find to be the next significant challenge that we face while conducting masking is the masking dilemma. As we know and understand, the masking dilemma can occur really for a few different reasons, or really just simply not being able to achieve effective masking can occur for a number of different reasons, but more specifically, the two true masking dilemmas that we will encounter having to do with output limiting, which we see on the left-hand side audiogram, and on the right-hand side audiogram, we see a bilateral true conductive hearing loss. Either way, not being able to achieve proper masking, effective masking, it's incredibly important to, I think, in the early stages of masking, once a student has really understood the concepts of knowing when masking is necessary, knowing the formulas, understanding the procedure itself, I think it's very important to introduce these two masking dilemmas to a student so they can experience them. It's one of these classic situations where until someone experiences a masking dilemma, they're not truly going to understand that it's occurring. So, these two audiogram templates here would be a near perfect example. For the left-hand side, simply put, we reach the limits of the audiometer, and we can't test beyond that point, we can't mask beyond that point, so that must be noted in the notes section of our audiogram. On the right-hand side, you know, when there is a conductive loss in both ears, it is very difficult to determine which cochlea is responding. Not to say that we discourage the attempt to mask and completing masking on both sides, but again, very challenging audiogram, often running into situations where we cannot effectively plateau, and thus reach a true threshold. So, again, very important to introduce. I would introduce, though, after some of those initial steps have been addressed and really mastered, if possible. Additional training tools that I highly recommend when you are first starting out with an apprentice would be, first and foremost, a virtual client testing tool. We often experience as apprentices struggling masking on a live client, I think there's that added, you know, pressure, but also, too, we notice that our apprentices, on average, take an additional 15 to 20 minutes, sometimes more, when they are first getting started completing hearing tests. This type of tool will give them the ability to speed up their processes, so we're working on time management, and we're kind of working through the steps of masking at their own pace before they're doing so with a live client. Again, building the confidence before they are working live with one of your clients, I think, is key for success. I also think it's key for success, again, building that confidence in the apprentice. And as mentioned earlier, I mentioned that I, for my students, had ordered a fathead, pinning the transducer appropriately on the correct side. Again, kind of a silly way to teach masking, but truly very effective, and something that I would highly recommend in the clinical setting if you are teaching more than one apprentice, of course, as well. And last but not least, closings. You know, if there are any outstanding questions or you are looking for some audiogram samples while teaching masking, please feel free to reach out to me. My email is kristin.wadsworth at hearusa.com. Again, we will be providing one CEU credit for this course, for this webinar, visiting ihsinfo.org. Thank you so much for attending. I hope that this was helpful for each of you that are embarking on teaching a student masking. It is certainly no easy feat, and hopefully this deconstructed that process for you ever so slightly, giving you the ability to work more effectively with your students. Again, thank you so much. A special thank you to my IHS team, the Institute Committee, as well as my partner on this series, Rebecca Kraus. Thank you so much, and we'll see you on the next webinar.

Train the Trainer

masking

hearing industry

Kristen Wadsworth

practical application

effective masking

training resources