today's presentation so that we may offer it on demand through the IHS website in the future. This website is available for one continuing education credit through the International Hearing Society. You can learn more about receiving continuing education credit at our website, IHSinfo.org. Click on the webinar banner at the homepage or choose webinars from the professional development menu. There you will find the CE quiz and information on how to submit it to IHS for credit. Also on the webinar page you will find slides to this presentation to help you gather the information you will need for the CE quiz. If you haven't already downloaded it, feel free to do so now. Tomorrow you will receive an email with a link to a survey. It is brief and your feedback will help us create valuable content for you moving forward. At the end of the presentation we'll move on to a Q&A session. You can send a question for Ted at any time by entering your question in the question box on your webinar dashboard. We'll take as many questions as we can in the time we have available. Now I'm going to turn it over to Ted who will guide you through today's presentation. Take it away, Ted. Hey, hey. Good to be here. It's always fun doing these webinars for IHS. I really enjoy doing these. This one today is on real ear measurement and it complements a previous webinar that we did on fitting methods a few months ago. Fitting methods have evolved with real ear measurement and real ear measurement has evolved with fitting methods. As you could see in the last slide here, I'll just share the agenda. We're going to be looking at the introduction to real ear. We'll talk about what we did before real ear measurement, functional gain. We'll talk about old real ear measurement when it started to replace functional gain, which used insertion gain. Then that real ear measurement transitioned or evolved into today's real ear measurement using in-situ output. Real ear measurement versus manufacturer software predictions is how we'll round out this topic today, followed by Q&A. So here we go. An introduction to real ear measurement. We often think we're so cool because we've got all this great digital hearing aid technology, but all too often, we let the software do the walking and the talking. We don't always verify, verily, verily, I say unto thee. We have to look at the proof, the truth with objective measures. Is the hearing aid doing what we think it is doing? See, the software given by the manufacturers is meant to put us in the ballpark of fitting, but manufacturers aren't here to sit beside us and fit the hearing aids. You're the clinicians. We are the clinicians. It's our job to fine tune and fit the hearing aid. That's not the manufacturer's responsibility, and in doing so, we need to use real ear. Think of a physician. If he or she sees a patient and thinks that the person has a disease, you got to at least take a biopsy to prove it. We are now in a science. We've evolved past the role of how does that sound? So if you look at this slide here, for example, on the left, you'll see some manufacturer software fitting, and it's got three lines on it showing three different targets, and you'll see the thinner lines showing how the hearing aid is approximating targets. If you look at the right, you'll see these plus signs in the center of the screen, and the solid line tracing through the plus signs is nowhere near the plus signs in the high frequencies, as would be suggested by the left-hand side of the graph. See, this is the thing. Right, wrong, or indifferent. It's not like you have to hit the targets of the fitting method, but with real ear, you know what you're doing, and you know how short you are or how close you are. Whether or not you want to hit the targets is another question, but at least with real ear, you know. Real ear probe tube measurements allows clinicians to objectively see the effect of ear mold changes, hearing aid settings. You don't need to rely on the subjective verbal reports of, sounds too tinny, or that sounds okay, or how does that sound? How does that sound? I mean, we're constantly, we're flying in the dark there. Think of the client who comes in. We're all clinicians, and we've experienced this before. Think of the client that comes in with his or her old hearing aid saying, the new hearing aids just don't sound like my old one. I want that sound back. Well, you could do real ear with the old hearing aid and find out just what is so special about that old hearing aid, and then you'll have the results in real ear. Now go to the new hearing aid and program it to match those results as close as you can. It's quite straightforward. Before anyone freaks out, no, hitting targets is not necessarily what you need to always do, especially for first time fittings. But rightly, wrongly, or indifferently, real ear measurements allow you to see, literally, what the client is hearing. I mean, how does that sound only go so far? We have evolved to become clinicians, and our science needs to complement the art of our fitting. We've got common objections to using real ear measurements. Equipment's too expensive. Well, it starts at around three grand. I think that's kind of a profit as to what one would get off after selling a few pairs of hearing aids, really. Don't have to? Look closely at your bylaws. Usually it's preferred practice. Audiologists don't have to. Well, imagine offering better services than them. Real ear measurement isn't valid for English as second language clients? What? I prefer to use client information sheet, like the COSI or some questionnaire. Now this trumps objective measurements would be totally beyond me. More common objections. Why should I? My competition doesn't. Well, again, God forbid you do better than they do. I listen to my clients. Yeah, right. That means I'm so darn good I don't need to use real ear measurement. Real ear measurement is a waste of time. Actually, it takes about 10 to 12 minutes to do it, and you get a lot of info in that short time. Manufacturer software already does the work. Hey, I've got a cottage on the edge of Lake Knot. I mean, it doesn't. It's meant to get you in the ballpark. The manufacturer software helps, and that's their job. They're helping you get into the general area of fitting for the client, but you are the clinician. We are the clinicians. It's not the manufacturer's responsibility to complete the fitting for our clients. We do that with real ear. So see the rest of this presentation. At the end, we'll talk about the manufacturer's software doing the work or not. Real ear basics, let's look at real ear components. All systems of real ear have similar parts. They all look different, but they all have similarities. Most real ear systems do both ANSI testing and real ear testing. As we recall, ANSI testing is used to measure the hardware of a hearing aid, the mic, the amp, the receiver, harmonic distortion, equivalent input noise, all that jazz. Real ear measures the function of the hearing aid with its software and everything else on the real ear. All systems have a loudspeaker, and if I draw with my cursor here, a loudspeaker that presents the sounds to the client who sits in front of the system. All real ear systems have probe mic assemblies, right and left, with tiny tubes that would be inserted into the ear canal. This is a close-up, and we'll talk about why we do calibration of real ear systems in the first place. All real ear systems, the piece that sits by the ear, these things have two microphones, a probe mic and a reference mic. The probe mic is associated with the tiny tube that goes into the client's ear. That's measuring the dB SPL at the eardrum of the client with the hearing aid in place. The reference mic, it's usually situated on the little box that houses the system, and this microphone here picks up the sound from the speaker that's being delivered from the speaker. For example, if you wanted that sound to be delivered at 70 dB SPL, the reference mic is making sure that that speaker is behaving itself and indeed delivering 70 dB SPL. That's the whole point. If the client moves closer to the speaker, the speaker sound will automatically get softer. If the client moves further away, the speaker sound will get louder, all so as to make sure or maintain that 70 dB SPL that you requested. Why do we calibrate in the first place? We calibrate in order to remove the effect of the tube from inside the person's ear canal. We do this by placing the probe tube right on top of the reference mic and having sound come out of the speaker. Calibration is done to remove the effect of the tube in the ear canal. Look inside the ear canal. You'll see it's a small space. It's only about a cubic centimeter, about less than the size of a sugar cube. And Americans, good old centimeters are about the width of your fingernail. About two and a half of them fit into an inch. Metric is the way to go, I mean, honestly. Freezing would be zero, boiling is 100. Makes sense, doesn't it? I'm joking. Anyway, here we go. You've got this tube in the ear canal, and this tube is going to be, you know, altering the acoustic properties a little bit in an enclosed space. So something needs to remove the effects of that tube, and that something is done by calibration of your instrumentation. I always like to know the whys of things, the W-H-Ys of things. How come you do it? Not just that you do it, the why. Note that as distance from the eardrum or tympanic membrane is increased, the effect is most pronounced for the high frequencies in the ear canal. This slide is here to show us why it's important to place the probe tube as close to the eardrum as we can. The bottom axis of this little graph here shows centimeters, from one to two to three. And again, an inch is about yay over here where I've put in my cursor. At any rate, the further back, the further the tube is away from the eardrum, the more this vertical axis here shows the reduction in decibels as a function of placement of the tube. So the farther we place the tube away from the drum, the greater the drop-off in decibels, and that effect is mostly pronounced for the high frequencies. See that? This is why it's important to place the probe tube close to the drum. The effect will definitely be seen on the high frequencies if you don't. The probe tube tip should be placed within six millimeters or five millimeters of the eardrum. That's a half a centimeter. There's 10 millimeters in a centimeter. There's 100 centimeters in a meter. There's 1,000 meters in a kilometer. I gotta like the system. At any rate, I digress. Six millimeters is about a half a centimeter. It's less than a quarter of an inch, okay? The probe body of most systems has a specific length. On this system here, made in Canada, it's called AudioScan, but lots of systems have them. This is about 29 millimeters long. The reason why is so that we can use that length, and you can see the ruler here, okay? And about two and a half centimeters is about an inch. You can see that, see? At any rate, the length of this box is meant to show you how far you should put the little black ring that's on this tube. It'll show you this little black ring right here. If you place that about 29 millimeters from the end of the tube, that way you will know that when you place this in the person's ear, that little black tube ensures that if it's placed at the tragus, for the average adult, the end of the tube will be in the proper proximity of the drum. There's a reason for everything. Some people, some systems have the speaker sit about three feet away, place the client about three feet from the speaker. Other systems, about 18 inches. It depends on your system, depends, depends, but that's all okay. So at any rate, the length of that probe tube tip, done in order to make sure that things are placed properly in the ear canal. And again, this is showing you on some particular system called the audio scan, but you'll find these similar properties on most real ear systems. Proper placement of the tube in order to get real ear unaided responses, and that was a measurement mostly used in old real ear. That's encountered in typical real ear. Real ear unaided response is when the tube is placed in the open, unaided ear canal. That was done to obtain the properties, the acoustic properties, the resonances of the client's outer ear canal. Followed by real ear aided response, with the tube held firmly in place, as it was with real ear unaided, now the hearing aid is placed in the ear canal on top of that tube, and the same sound comes out of the speaker, and now we measure the real ear aided response. The difference between real ear aided and real ear unaided is known as real ear insertion gain. And then we tried to determine with old real ear, does that insertion gain match the target? We don't really use gain anymore. We'll talk a little bit more about that in just a minute. Real ear to coupler difference is very important, especially for today's real ear. The reason we use RECD is in order to change DBHL values on the audiogram into DBSPL values, as seen on an SPLogram, and today's real ear uses SPLograms, but I'll get back to that more later on, too. Real ear to dial difference kind of dangles in the wind. Not too many people use that anymore, so I won't talk about it, but when these terms end in R, it's always important to realize that you're measuring DBSPL, not gain. You're measuring input or output. When the term ends in G, you're always measuring the gain, and that's always stipulated in terms of simple DB. Very important to understand these grounding principles, and I'll talk more about that, too, in a bit. What we did before real ear measurement, we used functional gain. Functional gain is the difference between aided and unaided behavioral thresholds. Behavioral meaning voluntary response, pushing a button, raising a hand. The old way we did it, and when you go through client files and see old audiograms, you might see these little letter A's drawn across. This is how we did it before real ear. This client has a typical mild to moderate hearing loss, sloping, might be typical presbycusis. We measured those thresholds under headphones. When that was done, we put the patient or client back in the sound room, and this time he or she faced a speaker, and tones were delivered from the speaker, warble tones. Came out of the speaker, and with the hearing aid in, yes, singular, hearing aid, because people rarely fit binaurally in those days, we re-measured thresholds again, aided, when the volume was at a comfortable loudness level, and there we go with the letter A, as you can see, going across the screen. And note that they're not reaching zero. We're not trying to make the person's hearing thresholds totally normal with this procedure. Why? This is called the spinal cord of all fitting methods. It's the half gain rule, as formulated by Sam Leibarger over a half a century ago. The idea was, in those days, all hearing aids were linear, they didn't use compression, but even with compression, you don't want maximum gain for average speech input. Consider this. What's average speech input? My father can beat your father at checkers, yackety, yackety, yackety, yack, there should be a cantor in the Catholic Church here. Anyway, average speech is about 65 dB SPL. If I add the hearing loss, if I add some 50 or 60 dB of gain to input of speech, which is 65, 65 and 60 is an output of 125. I'm going to be blasting the person to kingdom come. You cannot amplify average incoming speech by the full degree of the loss. What Leibarger found is that people preferred half gain, so that average incoming speech would be amplified by half the degree of the loss. The desired outcome was this. Aided speech output would thus, if you're supplying half gain to the input of average conversational speech, the idea then, the end result was that aided speech output would be placed nicely in the middle of the client's dynamic range. Let's define that two-word phrase, dynamic range. It always deals with intensity, decibels. It's the decibel distance between the floor and the ceiling of any system of any person. It's the dB distance. Normal decibel distance for normal hearing would be from zero down to 100 or so. The normal dynamic range for a normal hearing person is around 100. Depends on the frequency, but you know what I mean. For hearing loss, this person's dynamic range in the high frequencies is only from about 60 down to about 100, so his floor is elevated and his ceiling has stayed largely the same. I know it's an audiogram, O-D-D-I-O-G-R-A-M, it's upside down-ish. Too bad. I wonder who did that. Well, I know who did it. That's a different story, and I digress. But it is the upside down-ogram, and thank goodness for the S-P-L-O-G-R-A-M, because it flips things right side up again. We'll get to that in just a bit, but functional gain, the difference between aided and unaided behavioral hearing thresholds. The idea was a good one, to place speech output nicely in the dynamic range of the listener. Now we have, we graduated to real ear. It was the late 1980s, I remember well, when this system came in. It was the RASTRONICS, R-A-S-T-R-O-N-I-C-S. I remember it well. What we measured was insertion gain. We don't do that anymore. That's yesterday's news. But you know what? If we don't look at our history, we can't appreciate where we are today. Look at insertion gain. You can see on this graph, it's showing you now DBSPL on the left going from zero up. It's showing you frequency on the bottom from left to right. The yellow line is the listener's real ear unaided response with the probe tube inserted into the canal, open ear canal close to the drum. The blue is the same sound coming out, but this time the hearing aid is placed on top of the tube. And now the real ear aided output is measured. Input and control of the hearing aid was set to a comfortable loudness level, a comfortable listening. The input sound, it's important to note, in this case would be 55 dB. The outer ear canal unaided is doing nothing to these frequencies at 50 dB, 55 dB input, nothing, nothing, nothing, until around 1,500 hertz, all of a sudden the outer ear canal gets excited and it begins to resonate like a wine glass at Christmas when you're rubbing the finger on the top of it. Your outer ear has its shape so that it can literally and deliberately offer a gift of around 20 dB of gain for the high frequencies. Why? Because we speak. And the consonants are soft. The outer ear is a gift from God or the great evolutionary divine source, whatever you call it, because we speak. If we didn't speak, we probably would have dog or cat's ears. Our ears have the weird folds and shape that they do in order to give us this resonance so that we can better hear speech. Isn't that special? Anyway, aided response minus unaided response gives the black dotted line real ear insertion gain. And did that match the target as shown in red here? And look at the numbers of the target from 10 to 15 to 20, 25 to 30. It's the same as functional gain as shown here on this slide. It's not that the fitting methods changed. Real ear didn't do that. Real ear is just a different method of achieving the same goal. The targets here would be the letter A's. If your aided thresholds were half gain in this case, great. That's what you'd want. Well, same thing with older real ear. If your target, if your insertion gain matched your target, which is showing you deliberately now for the sake of example, the same numerical results as I did with the functional gain picture, then you were good to go. Like an old salmon, you could swim up the stream to die. I hit target. Yay. Be careful, because this is not a very good counseling tool. Real ear measurement looks a lot at real ear unaided response or outer ear canal resonance. You can see here the natural amplification of soft, high-pitched consonants is given about a 20 dB lift. And it varies a lot among individuals, but it has a peak at around 2700 Hz and it starts at around 1500 and it starts to plop off at about 4000. And this is why it was so important to put that tube in closely, because if you didn't, you'd lose the resonance at around 3000. It would start to drop off like so. Anyway, that was of a big concern and it still is. The proper tube placement is important. Outer ear canal resonance. Sound coming out of a speaker. What's wrong with this picture, folks? Those who say the tube isn't far in enough are correct. It's not in far enough. Sound coming out of the speaker into the ear canal. It's picked up by the probe mic and the resonance of the outer ear canal is thus measured. The sound is changed from frequency to frequency to get that measurement. Here's the hearing aid now in place. The tube hasn't been moved. Hearing aid is in place. Same sound is repeated from the speaker, like a sweep tone, they called it. I always think of sweeping the porch when I think of that, but I don't know why they say sweep, but anyway. And the sound is measured in the ear canal. Again, that would be real ear aided response. Note, the resonance, the real ear unaided response is lost when the hearing aid's in place because it's plugged up. You've lost that love and feeling. It's gone, gone. It is because you've plugged up the ear. Nonetheless, that's what the real ear measurement did. The old way of doing real ear, real ear unaided response compared to real ear aided response. Note the input circled in red here, 55 in this case. The resonance isn't going to change with changes of intensity. It's just the resonance is the resonance. So nonetheless, they chose 55 because it was over ambient room sound pressure levels, which is about 40. So you want to be delivering sound more than that. This was the old way of doing real ear. Real ear aided response minus real ear unaided response on the right yielded real ear insertion gain. What is that as a definition? It's the difference between aided and unaided SPL at the tympanic membrane. Note, it's not a behavioral measurement now. It's a non-behavioral measurement. It's not difference between thresholds. It's the difference between aided and unaided SPL. Real ear aided response, it's an in-situ output measure because it's done with the hearing aid in situation, in place, when you're measuring the output of the hearing aid. We subtracted the real ear unaided response from it in order to get what we call the real ear insertion gain. But that's yesterday's news. Today's real ear measurement doesn't use RER. It only looks at real ear aided response. Gain is a means to an end. We do today only these kind of measures, in-situ output. Hearing aid in situation, in place. We're measuring the output of the hearing aid with the probe tube in the ear canal. We're not looking at the gain anymore. Look at this graph. It's called an SPL-o-gram. The bottom of the graph is showing you normal hearing in dB SPL. As we recall, 0 dB HL on an audiogram actually represents various different decibel amounts, doesn't it? That's because of the resonances of the outer and the middle ears. At any rate, those are all calibrated into an audiometer and we have 0 dB HL placed at the top of the audiogram. The audiogram is that in dB HL, but this is an SPL-o-gram. Decibels on the left going from 0 up to 120 on the left. Frequency across the bottom axis. Normal hearing is now on the bottom. The floor, the ceiling of loudness tolerance is these asterisks. The decibel distance, the dynamic range from the floor to the ceiling is around 100 dB, isn't it? Now the person with hearing loss, here's his or her audiogram placed on top. You can see that compared to normal, his floor is elevated, and yet the ceiling hasn't really changed. So his dynamic range, his decibel distance has been squished. That, by the way, is why hearing aids use compression to fit a big dynamic range and squish it into a smaller one. But that's another topic. Anyway, look at the yellow and orange lines. Those would be the targets for speech. The orange line would be for soft input speech of 55 dB. Notice that we want the input of 55 plus the gain of the hearing aid to yield an output that barely hugs, that barely is above the threshold. That means the person can barely hear soft speech. That's normal, because a normal hearing person can barely hear soft speech. So why should the hearing impaired person experience anything different? The yellow line would be where we'd want to position or place average input speech of about 65 dB SPL, so that its output sits in the bottom third, roughly, of the client's dynamic range. The game changer of all of this was the DSL fitting method, desired sensation level. DSL is a fitting formula, and it came up from Richard Seewald, Ph.D., a professor, now retired, but at Western University in Ontario, London, Ontario, Canada. I find it kind of interesting that the two main fitting methods of the world, NAL and DSL, come from those big pinko countries on the globe, not from the United States, but that's, I'm just bugging you guys. At any rate, I imagine some people are from Canada here, so DSL took a dim view of gain and REUR, and real ear insertion gain, because the thresholds were obtained with headphones, circumaural TDH39s or inserts, ER-3As, and when you're plugging up an ear with a headphone, you're messing around with the REUR anyway, you're screwing it up. REUR is bypassed when testing with headphones, so therefore, real ear insertion gain targets are based on thresholds that didn't incorporate one's real ear unaided response in the first place. So if you're looking at real ear insertion gain, then it would seem that unaided thresholds should be obtained in a sound field, because only in a sound field are you really incorporating one's open ear canal response. You get it? So if you're not using, if you're using, you're getting real ear insertion gain by utilizing real ear unaided response, subtracting it from aided response, you're getting real ear insertion gain, but hey, if you're not using real ear unaided response in the first place when you're testing thresholds, why the Sam Hill are you using it when you're measuring the hearing aids? So, you know, let's do apples to apples instead of apples to oranges. So this was one of the main criticisms of using real ear unaided response. With insertion gain, it's critical woes, the devil is in what it doesn't say. It doesn't talk about the audibility of speech. I mean, in this way, it's even worse than functional gain. Look, you've got the real ear unaided, real ear aided, you have insertion gain here, you can see how it's giving too much mids, not enough highs, but nonetheless, what does this tell? Even if you were matching targets, what does it tell you about the audibility of speech when aided compared to unaided? Not a very good counseling tool. Probe tube measures today use only one of those measures, real ear aided response. It's actually easier than subtracting unaided response in order to get real ear insertion gain. In-situ outputs are measured for soft inputs, average inputs, and loud inputs. Gain is yesterday's news. Gain is just a means to an end. Output rules. Output is the groceries delivered to the tympanic membrane with the hearing aid in place. I mean, looking at gain is like me saying to you, did you get the bread from the store? Yeah. Did you ride your bike? Did you walk? Did you drive a Volkswagen or did you drive a Cadillac? Well, who cares? Did you get the bread? Gain is just how did you get to the store? Output is the bread. The difference between gain and response, when you're looking at real ear terms and real ear aided response versus real ear insertion gain, gain is a difference measure. We're coming to that topic I had at the beginning of this conversation here. Gain is a difference measure. It's a relative value. Gain is indicated in simple dB. It's the difference between input and output. Input plus gain is output. So gain is always specified simply as dB. Response, when the real ear term ends with an R, it's always dB SPL. It's an absolute measure. We remember our acoustics. What's zero dB SPL? It doesn't mean no sound. Never think that. It means the softest it took for a normal hearing adult to hear a 1,000 hertz tone at one meter, okay, one yard, one meter distance from a speaker with two ears. There's three things there. It's the softest it took to hear a 1,000 hertz tone at one meter from a speaker with two ears. That's the holy grail. That's the ground. All other dB SPLs are referenced to that ground. So on graphs, gain, which is a relative term, is always specified in dB. I can give 50 dB gain to a 10 dB SPL input, so that 10 plus 50 is 60 dB SPL output. I can give 50 dB of gain to a 20 dB SPL input, so that my sum total output is now 70 dB SPL. See, gain is just relative. The 50 is the 50 in this case. So can you add dBs? Yes. So you can if you're adding input dB SPL plus gain in dB yields an output dB SPL, just like 1 plus 2 is 3. But here's the kicker. You can't add decibels. You can't add two dB SPL values together. One machine making 80 dB SPL in a corner of a room added to the noise of another machine making 80 dB SPL in another corner of the room. Well, here the sum total is closer to 83 dB SPL. Get it? So anyway, input plus gain is output. It's just a digression here, but I think it's important to grasp these concepts. Here's an example here. What's the gain of 1,000 hertz for each of these three inputs here? The green lines are showing you three target outputs. The red, the blue, and the black are showing you how the hearing aids are doing in matching those targets. On the right you'll see three inputs, 50, 70, 90. Well, the bottom green line shows the requested or desired output for an input of 50. Look at 1,000 hertz. The output for a 50 dB input is 75. Well, that's a gain of 25 because 75 dB SPL and you're minusing the input, you're getting a 25 dB gain. Look at the top green line. At 1,000 hertz it's 95. Well, an input there was at 90. 95 minus 90 is only 5 dB gain. So they're two different animals, gain and output, but today we concentrate on output. See sound or speech mapping in dB. The SPLogram, the audiogram is displayed right side up. In-situ, real ear aided response becomes the main focus. Everything in terms of dB SPL now. Aided speech can be shown. Aided speech is placed on a dynamic range and it's compared to unaided speech. It's a fantastic tool for counseling. Here's speech or sound mapping. You've got normal hearing on the bottom, the dotted line. The red zeros or O's are the thresholds. Must be a fairly flat loss then. And look at the target for soft speech, the target for average speech, the target for loud speech. Make sure you keep it below loudness discomfort levels, the asterisks. And now you've done three different real ear aided response measures. In reality, the average speech should not be placed in the center of the dynamic range. It really should be closer to the bottom third, but this is just for illustration. It's all about LTAS, Long Term Average Speech Spectrum. You can see here that speech has most energy, most loudness in the low frequencies on the left, the vowels, and less energy in the high frequencies. You can see that speech, the dotted lines are showing you the dynamic range of speech. Speech has peaks and valleys. My flapping gums to you are that some of the sound is louder, some of the sound is softer. Unlike noise like a fan or an air conditioner that's steady in intensity over time, that's different because that noise is steady in intensity over time, whereas speech is rapidly changes in intensity over time. Look at these two examples. The top is showing you a pure tone, but think of an air conditioner. Look at the bottom here. Speech. The pope ordered his cutlery too late. It's going up and down, fluctuating madly. That difference, by the way, explains why the average of speech, the solid red line here, is not in the center of the dynamic range of speech. See, speech has a dynamic range too. It's its decibel distance from its softest to its loudest. So that's what dynamic range always means. Anyway, this is how hearing aids with digital noise reduction work. They determine if the sound coming in is more like the top wave, steady in intensity, oh, then it must be noise. Reduce the gain. Look at the bottom. Oh, it's changing rapidly in intensity over time. Must be speech. Amplify. That's basic digital noise reduction, by the way. It uses the acoustic characteristics of the sound coming in. Nonetheless, back to the game here. Speech mapping on an SP elegram. You can see the normal hearing on the bottom, client thresholds in blue. You can see the ceiling, the asterisks, and you can see where you'd want input average speech to be placed. Targets for amplified speech in the lower third of the dynamic range of the listener. Look at unaided speech. L-TAS with a U behind it. You can see how this listener can hear the low frequencies, but he can't hear the highs. And it's a fantastic tool for counseling because you can say you want to lift those highs up to where they belong. We don't need to touch the lows. We've just got to lift up those trebles, and that way we can describe to the caregiver or loved one or the client, him or herself, what the hearing aid is doing, what its benefits are. Unaided speech. You can see it on the left. It's a different real ear system. They don't all have to be the audio scan. There's all kinds of them. Anyway, on the left, you'll see the dynamic range again. The floor on the bottom, the ceiling on the top, and it's showing you where average speech inputs would be. On the right, you can see aided, where the aided speech is. You can see the hearing loss is now elevated on the right graph. You can see the dynamic range. The floor has risen. The ceiling hasn't changed. And you can see where you'd want target speech to be, average input speech. In this case, I'm amplifying a bit too much. The output is over top. It's too much. I've got to reduce it a bit. Interpreting the response curve. Here's another system, a unity system. It, too, is look at the right-hand graph. It's showing you the gray area. That would be the target for amplified speech. And you'd want to make sure that your output is situated nicely in that target, your output for average speech inputs. Here's another example, unaided speech in green on the bottom. You can see it. If I can bring my cursor there, you can see the hearing loss going across. You can see that this person with the hearing loss cannot hear average unaided speech. And with the hearing aid, you're amplifying it so it now is in the listener's dynamic range. Again, this is a little bit too much. I'm amplifying so that the aided output is halfway in the dynamic range. That's a bit much. It should be reduced. Real ear-to-coupler difference is another term. You know why we use it? It's what changes DBHL thresholds into DBSPL thresholds on the SPLogram. When you're testing with insert headphones, RECD is used to achieve this purpose, to change HL into SPL. It's the difference between a sound in a closed 2cc coupler, because that's how insert headphones are calibrated on a 2cc coupler. And it's the difference between the sound in a closed 2cc coupler versus the sound in a closed ear canal. Well, 2cc couplers are a little bit of an over-exaggeration of the actual air space in a closed human ear canal. In a closed human ear canal, the volume is closer to 1.5 cubic centimeters. So there is a difference between the SPL in a 2cc coupler versus the SPL with inserts inside of an ear canal, or a hearing aid inside an ear canal. And the 2cc coupler values are constant, but since real ear unaided responses vary considerably, real ear-to-coupler differences will vary as well. When you're plugging up the ear canal, different strokes will occur for different folks. Real ear-to-coupler differences are especially important for fitting children who have smaller yet ear canals, because smaller canals result in even more sound pressure level in a closed ear canal, and higher resonant frequencies. So real ear-to-coupler differences are always measured in children when you're doing fittings. In adults, run-of-the-mill, you can often rely on average real ear-to-coupler differences. But maybe you have a small person, or maybe you have a person with a mastoidectomy, or maybe you have a person with a large ear canal. Better measure the RECD. But your equipment, and by the way, it takes about five seconds, it's easy-peasy, Japanesey, everybody does it, so hey, everyone's doing it. Real ear-to-coupler difference, RECD, what is it on the average person? About 5 dB in the lows. Look at the top here, you'll see the coupler response, I'm tracing with my cursor, and you can see the real ear closed response. Same sound coming in, the difference between the sound in a 2cc coupler versus the sound in a closed human ear canal, about 5 dB in the lows, below 1,000 Hz, and about 10 dB in the highs, above 1,000 Hz. The bottom is showing you average RECD, look, we're on tracing here, and it's about 10 dB in the highs, and about 5 dB in the lows. Your equipment automatically puts this in, if you've elected for it to do so. Anyway, visualizing aided speech, three general rules, soft inputs, average inputs, loud inputs. Soft inputs, 55, you want to keep the outputs just above the thresholds, because normal hearing people don't hear all of soft speech, neither should hearing-impaired people wearing hearing aids. In the blue here, average input speech, make sure that it is all within the dynamic range, especially for Matthew, Mark, Luke, and John, 5, 1, 2, and 4. Make sure you are at the targets there. Generally, targets for NAL versus DSL-5 are going to be very close for adults, barely a man on a flying horse would be hard-pressed to notice the difference between NAL, NL, 2 targets, and DSL-5 targets. Basically, targets for average speech input will be about a third above the threshold in the dynamic range. Loud inputs, make sure the outputs are kept well below loudness discomfort levels. Here is an example, outputs for soft input speech. You can see that the outputs are hugging the thresholds. That's normal. That means the person hears about half of soft aided speech. Here are the outputs for average input speech. You can see that they are in the bottom third of the dynamic range. Actually, they could even be lowered down a tinge more from this, it wouldn't do too much harm. What's wrong here, aided speech for average inputs, look at the bottom right, 65 inputs. The outputs are a little high, they are sitting in the middle of the dynamic range, that's a bit much. We can complete this one here talking about real ear measurements versus manufacturer software. Here is the rub, manufacturer software prediction often paints with rose colored glasses. It doesn't mean they are not nice people. Manufacturers are not there to fit your hearing aids, they are there to help you fit your hearing aids. You are the bottom line. Notice the left is showing you a pretty picture, three target aided outputs, and the hearing aid response is all really close to those. Look at the middle one. See how the targets are fairly close to the requested outputs? Look at the right screen now. The plus signs are the targets for average speech inputs. They are a little high, it's old DSL, it's DSL 4, but nonetheless, look at what the hearing aid is doing on the right, it's way shy of targets. Now again, I'm going to say that the idea is not that you necessarily have to hit those targets, because maybe the client is going to wind up and punch you in the head. It's too loud in the highs, that may be true. The point is, real ear shows you this, rightly, wrongly, or indifferently, it gives you the tools as a clinician to make up your mind with the client about what you want to do. I loved having students at Conestoga College, because I could use them as slaves to give me desired results that I could use in PowerPoints to do on webinars. This student looked at NALR, the old fitting method on an old real ear system, and you can see the purple here on the left is real ear unaided response, and when fitting according to manufacturer software, here's where they said to put it. When she chose NAL2, or I should say NALR, as a fitting method, the software programmed the hearing aid with the hearing loss, the audiogram binked in as well, and this is the output she actually got. And so this would be the gain she got on the bottom. Look at the insertion gain, how shy it is of target. Look at how much adjustment was required in order to get a greater real ear aided response, and consequently a greater real ear insertion gain. Same on the right with the SPLogram, when programmed to fit with DSL, the aided outputs were way below these dots being the target. The output had to be adjusted significantly in order to really get closer to targets. Here's another example. Normal hearing on the bottom, your patient's threshold shown in red, the discomfort levels the blue Xs, the targets are the plus signs, again, pay no mind that they're halfway in the dynamic range. It's an old, it's just an example. The fact is that when these things were binked into the software, the audiogram, the fitting formula, everything else, here's where the output was in brown, way below target. Look at how much it needed to be adjusted. Look at another example here. DSL programming with the software, here's what you ended up getting with readjustments. And on the right again, so DSL here is on the left, NAL, NL1, the old NAL formula shown on the right. These examples are a few years old, but in every case, the manufacturer software did not accurately place aided outputs to where they really needed to be, especially for the seasoned listener, the experienced listener. So I mean, for the new listener, you're not going to want to hit major targets anyway. You're going to deliberately wean them in, but the point is RealEar shows you. Here on the left again, another example, programmed gain and readjusted gain on the bottom on the left. And again, showing on an SPLogram, initial programmed output and readjusted output in order to really hit the targets. So references for this talk, I thank you all for listening and for putting up with the technical difficulties halfway, but actually we had it all planned that way, didn't we? References are me, myself, and I. I had a lot of clinical experience over the past year and got reacquainted with the new advancements in hearing aids. It's been my pleasure to talk to you. I really thank you all for listening today. Ciao, and have a good one, and feel free to ask questions. I'm going to ask the audio scan for many of the pictures that they lent to me. Please feel free to enter questions that you'd like, and I'll do my best to answer them. All righty then. Here we go. Great. Thank you, Ted. Thank you. Ted, we're so excited that over 370 of your fellow colleagues have joined us today on this webinar. We do have some time for just a few questions. If you do have a question, please enter it in the question box on your webinar dashboard. Ted, our first question comes from Constantine, and Constantine wants to know, are there any recommendations for setting the MPO on a hearing aid? Are there any recommendations for setting the MPO on a hearing aid? Any specific ones? Connie, how are you doing? Anyway, what I can say to you is I generally, I'm kind of old-fashioned, I use speech to get my UCLs and DBHL, and then I tend to add about 15 to that to get an MPO of a hearing aid. I mean, that's the rough way to do it, and I do that simply because overall the average decibel difference between DBHL and DBSPL across the frequencies is around 15, 10-ish to 15-ish. So that's why I tend to add 10-15 to my UCLs in order to set my MPO on the hearing aid. Great. Thanks, Ted. Ted, our next question is from Jay, and Jay says, if we are measuring OSPL in the eardrum, does it mean we need to have different values of outputs for different ear canal volumes in order to ensure that the right amount of OSPL is processed at the TM? I'm trying to digest that question. Let me first say we don't measure, oh yeah, OSPL, now I know what you mean by that. We're measuring the output at the drum. Now read the question to me again, I'm just trying to process this one. Do it again. Thanks, Ted. Okay, I'm going to read it again. I'm going to read it again, Ted. If we are measuring OSPL at the eardrum, does it mean we need to have different values of outputs for different ear canal volumes in order to ensure the right amount of OSPL is processed at the TM? No. In a word, no. The equipment is measuring the OSPL, period, and it's measuring it in any different size of ear canal. So the size of the ear canal is automatically factored in to show what OSPL you're getting with that particular hearing aid. So basically, you know, because you've estimated what the loudness discomfort level should be, and now on your resultant SPLogram, you're able to visualize what OSPL you're getting at the eardrum and make sure that stays below the loudness discomfort levels as you've indicated on your SPLogram. That's all you really need to do. The size of the ear canal is automatically factored in. Thanks for asking. It's a good question. Great. Thanks, Ted. Ted, our next question comes from John. John wants to know approximately how many audiologists and or HIPs use real ear today? Oh, you know what, I'll bet you half. And I'll bet you that number doesn't really differ between audiologists and HIPs. Bet you, bet you dollars to donuts. It's really a shame to see people working in a clinic not using real ear. We've entered this decade, and it's time to walk with the developments that have taken place. We are no longer selling hearing aids out of the trunks of cars or motel rooms. We're no longer relying on, how does that sound, how does that sound? And we need to, we are clinicians with education. We've gotten our board certified and HIS certification. We've got our degrees, our college diplomas, what have you. Let's walk with it and show that we have both an art and a science. It's time. Good question. Thank you. Thanks, Ted. Ted, our next question is from Michelle. Michelle wants to know why does real ear show different results from manufacturer fitting software predictions? That is, why the difference, why is there a difference in the first place? Manufacturers are doing their best to estimate. They're adding up the audiogram degree of loss, then plus the gain you're going to need or the output required by some specific formula, and then they're factoring in, is the hearing aid a CIC, is it a receiver in canal, is it a BTE, and they're factoring in all these things like 1 plus 2 plus 3, whereas when you're doing real ear, all of these things are being measured together in real time. Therein lies a difference. A second reason why is manufacturers, the last thing they want to do is overfit. So they tend to err on providing less than you'd think. And they do that especially for HIS. Now, I'm a little cynical about that because it makes the hearing aid sound less sharp and it makes the hearing aid sound just barely audible, but at any rate, I don't blame them really. I just think that the onus lies on the clinician to use the software to get you in the ballpark and then verify with real ear. That's where our role comes in, and it's not the manufacturer's responsibility to complete the fitting of a hearing aid, it's ours. Great. Thanks, Ted. Ted, our next question is from Peter. Peter wants to know, how do we insert probe consistently? Well, a lot of that was at the beginning of the talk where I was talking about where to put that little black ring on the tube. You want to make sure that the end of the tube, the probe tube, is within about 5 millimeters of the eardrum. That's about a half a centimeter. That's about a quarter of an inch. I mean, you're talking small here, okay? And the reason they have the box on the probe module, the little black box or whatever, is usually the length that you should put that little black ring from the end tip of the probe tube. And then, with that having been done, when you're putting the probe tube in the ear canal, if you place the black ring right at the tragus, you will be fairly comfortable in knowing that in the average adult, the end of the probe tube will automatically be within the requested distance of the eardrum. Good question, though. Great. Thanks, Ted. Ted, our next question is from Delmar. You're welcome. Delmar would like to know, he would like you to explain how RECD is performed. Ah, RECD is performed usually by taking the 2cc coupler response, which is usually a fixed value, and then immediately you take the tube, the probe tube, and you hang it on the guy's ear, you insert it properly, and then you take an insert headphone, and you plug that on top, an insert phone on top of the tube, and you run the same sound that way as you did through the 2cc coupler. The difference, then, is the RECD. Now, that's if you've decided you want to measure the RECD. Many people with the average adult and an average canal elect to use the already stored average real ear-to-coupler difference, which is about 5 dB below 1,000 Hz, and it's about 10 dB above 1,000 Hz, roughly speaking. Average RECD is used, again, in order to change dBHL values into dBSPL values. So if you've got thresholds of X and Y and Z, or Zed in Canada, on the audiogram, RECD is used in order to plug those thresholds onto the SPLogram. Great. Thanks, Ted. Ted, we have time for one more question. Our last question is from Sarah. Sarah would like to know, what's the best fitting method to use with real ear? The answer is, there is none. Fitting methods are philosophies. Philosophies are like faith, like religion. What's it best to be, a Catholic or a Protestant? Basically, the fitting methods evolved because people didn't have the visualization of an SPLogram. All they had was functional gain. So they were trying to come up with rules so that you would accurately place aided speech nicely into a client's dynamic range. Right now, both DSL-5, the latest version, and NAL-NL-2, the latest version of now, they're very close to each other in terms of targets. You can hardly tell the difference. Both of those fitting formulas place average aided speech well within the lower third of a client's dynamic range. But they both ensure that aided speech is audible at 5, 1, 2, and 4. Both of them place soft aided speech barely above the threshold. So really, the answer is, none of them are better. Pick one and stick with it. Great. Thanks, Ted. Ted, thank you very much for an excellent presentation. And thank you to everyone for joining us for the IHS webinar, Real Ear Measures, Yesterday and Today. If you'd like to get in contact with Ted, you may email him directly at tvenema at shaw.ca. For more information about receiving CE credit on this webinar, please visit the IHS website at ihsinfo.org. Click on the webinar banner or find more information on the webinar tab under professional development. IHS members receive a substantial discount on CE credits. So if you're not an IHS member already, you will find membership information at ihsinfo.org. Please keep an eye out for the feedback survey you will receive tomorrow via email. We ask that you take a moment to answer a few questions about the quality of today's presentation. Thank you again for being with us today, and we will see you at the next IHS webinar.

real ear measurement

fitting hearing aids

objective measures

verification

history

evolution

components

calibration

ear canal

performance