1 Wow, after all these years of reading about your measurements, I feel a bit honored to be sitting here with you, KEMAR… oh, excuse me, is it okay if I simply call you KEMAR?
Oh yes, the whole Knowles Electronics Manikin thing gets to be a bit drawn out and cumbersome. To be grammatically correct, however, I think it should be “the KEMAR.” You've probably also heard me referred to as the “KEMAR manikin,” which makes me a manikin-manikin, except that the KEMAR name became a registered trademark, so it really is no longer an acronym. You then need the manikin designator to describe what I am.
And, I guess if we go by the trademark version of my name, then you don't really need the “the.” It's all so confusing to me. But, by the way, if you check out a good dictionary you'll see there is a difference between a manikin and a mannequin. I'm definitely the former, although some people insist on calling me the latter. I can assure you, I'm not that great at modeling clothes—especially pants!
2 So, tell me, how did you get the name KEMAR?
Well, that's an interesting story. As you may know, I grew up in the Chicago area. At first I was just called “the manikin,” but as I started to take shape, people starting calling me “IRPI.” That was because the work on me was being conducted at Industrial Research Products, Inc., a research and development company that pre-dated and was later absorbed into Knowles Electronics. My name was later modified to the more pronounceable and descriptive acronym IRMAR. But then, Knowles Electronics became an important part of my promotion, so KEMAR was the logical choice. That was okay with me, as I never really felt like an “IRMAR” anyway.
3 Before we go any further—the buzz on the street is that you've moved to Europe. What's the deal with that?
I certainly did, and I'm enjoying every minute of it! Denmark is wonderful! Great pastries, and did you know it's okay to drink beer at lunch here? The tone of your question makes it sound as if moving from the U.S. to Europe in your 30s is an unusual thing. Seems to have been okay for the likes of Madonna, George Clooney, Johnny Depp, and a host of NBA players.
To fill you in on the details, I'm now part of the research team at Gunnar Rasmussen's Acoustic Systems—we call ourselves G.R.A.S. I'm living in the city of Holte, which is about 15 miles north of Copenhagen. It's a high-tech area, which gives me a youthful spirit (not that I'm old). The company produces a lot of front-end acoustic products such as microphones, pre-amplifiers, and signal conditioning devices, so I fit in pretty well. They even have an artificial mouth (don't ask!). My new boss worked in product development at Bruel & Kjær back in the 1970s when I was birthed, and he did some work with me then, so we have a long history together.
4 Glad to hear that things are going well. Let's reminisce a bit. Do you remember your development?
Well, I was told that it really started before I was born. Hugh Knowles, the president of Knowles Electronics, had long believed that we needed to express hearing aid performance differently from how it is displayed in a 2-cc coupler. In fact, he presented papers on this topic in the 1960s at AHSA conventions, which in general fell on deaf ears.
As I recall, my development got started seriously around 1970 when Hugh returned from an IEC standards meeting in Europe. Much discussion at this meeting had centered on the fact that most hearing aids were now head-worn instruments, and so there was a real need to have hearing aid performance measured under more realistic conditions than inside a test box. Recall, it was also about this time that CROS-type eyeglass instruments were fairly popular, and directional-microphone technology was just being introduced—two more products that certainly needed to be tested on a head.
Finally, it was about this time that there finally began to be a convergence of interest in producing a mechanical structure that replicated the acoustic performance of a human ear. Hugh and the folks working with him simply decided to do it, and that was when efforts began to collect average human values so that I could be built.
As you probably know, I certainly was not the first manikin to be built for the purpose of acoustic measures. For example, not too many years before I was born, Benjamin Bauer developed a manikin somewhat like me, although I can't remember its name. It had a head and torso, and an open-ear transfer function that was fairly similar to my response. Among other things, Bauer was conducting research on developing “spatial earphones,” including earphones that could be used underwater. This manikin was larger than me, as it matched the average dimensions of the original seven male astronauts of the NASA Mercury program. To be honest, I sort of wish I had been modeled after famous people, but, oh well…
5 So, were you actually built in Chicago?
The folks at IRPI just outside Chicago designed me, and then the Richard Rush Studios in Chicago did the sculpting, providing a clay model from which molds were ultimately made for my production. In case you're unfamiliar with this studio, it was known worldwide for its work on dioramas and full-size environment simulation installations, such as the ones at Sea World. For many years after my initial construction, the people at this studio continued to provide my parts, including my molded fiberglass torso and head, neck adjustment rings, and my molded “rubber” pinnae.
6 Since we're talking about your appearance, I recall that in your early JASA article you were wearing a wig. Is that what you prefer?
Remember, my job is to provide measurements that are similar to the “median adult human.” What I prefer, therefore, doesn't always coincide with what I'm paid to do.
To be honest, in the early days, I really thought I looked better with a wig—not a dopey mop like most audiologists put on my head, but a good looking rug like Sean Connery wears. I've changed my thinking lately, however, and bald is just fine. Because of my 30-year Chicago connection, I got to know Michael Jordan, who you have to admit is a pretty cool-looking bald guy.
I know, you're here for the science, so let me tell you, unless you're concerned with the frequencies of 10,000 Hz or above, it really doesn't matter if I have a wig on or not.
7 One more thing about the JASA wig photo. It was a curious looking wig. It didn't really identify you as a man or a woman. I have to ask, what is your gender?
That's rather personal, but I've spent so much of my life sitting around naked, I don't have too many secrets. You weren't listening carefully, however, when I said earlier that I am the “median adult human.” The primary measurements that went into my head and face dimensions were taken from a 1950 U.S. Air Force survey of 4000 males (mean age 28) and 852 females (mean age 20). The people who designed me were careful that all of my critical facial dimensions were correct. When compared to both the male and female measurements, all of my measurements were within 4% of the median. So, as I said before, I'm pretty much a median kind of guy (or gal)!
And back to the naked part for a moment—my acoustic measurements don't change significantly whether or not I wear clothes. They even put stuffed bras on me in some of the tests, and that didn't matter either. But, you do need to know that you can gender me a little by changing my neck rings, which change my shoulder to tragion distance. The median male distance is 18.8 cm, the median female distance is 16.3 cm. So I have two removable neck rings, each 1.27 cm. It's a not a big deal, but because of torso reflections, it does change the frequency response measured on me a little in the 1200 to 1500-Hz range. So, if you put in two neck rings I'm a guy; no neck rings I'm a girl. Many people use one ring when they do testing with me. Maybe I should go by “PAT.”
8 Okay, I'll try not to genderize you too much. But let's talk about your head for a moment. It seems rather hard and unnatural to me. Is this okay?
Good question. I know where you're going with this. You're wondering if the surface impedance of my head makes me less real-ear for hearing aid measurements. And you're right, I'm supposed to be the median human, yet my head is a little harder than average. For those of you who haven't touched me, I'm made of a hard polyester-fiberglass material.
I'm pleased to tell you, however, that back in my development stage, the folks at IRPI looked at this factor. In fact, they made a replica of my head and had a duplicate made using General Electric silicone rubber foam. The acoustic impedance of this replica was about the same as soft human tissue. When they tested me in their laboratory, they found that the differences between this replica's soft head and my hard head were all within 1 dB! So, acoustically, hard heads can be okay!
9 And what about your pinna? Or should I say pinnae?
Well, as anyone who has worked with me knows, they are removable and made of a softer rubber. My first pair was fabricated by taking complete impressions of the ears of 24 subjects (12 males and 12 females, available from the staff of the IRPI company). Extensive measurements were taken to obtain a “standardized” pinna that was both dimensionally and acoustically average. Again, the goal was to determine the “median ear.”
All those data were published by Mahlon Burkhard and Rich Sachs in the 1975 JASA article you mentioned earlier. Oh, by the way, the ear that best fit the median values belonged to Sheila Sachs, the wife of Rich Sachs, one of my developers.
As time went on, there seemed to be a concern among people using my first pair of ears; they thought they were too small. So, the folks at IRPI went back to the original impressions and selected a second pair of ears that were two standard deviations larger than the original median values, although acoustical performance was still the main controlling requirement. These were called the “two-sigma ears” and these larger pinnae are most commonly used today.
Over the years, my pinnae have been manufactured in different colors, and I've heard there are at least four different colors out there. I'm not sure, however, that there is a clear color-coding system for small versus large.
10 Obviously, your fame is related to your head and torso, and pinnae, but don't you think the Zwislocki coupler contributed to your success?
Most definitely. It's true that before my time, pretty much all hearing aid measurements were conducted using the 2-cc coupler. You're probably aware of Romanow's 1942 article about the 2-cc coupler, considered the seminal reference on that topic. Don't forget, though, even then he talked about the importance of including “real ear” factors. But you're right, when I appeared we brought two new things to the table, two good things I think: testing on a manikin and using a coupler that was more representative of the real ear.
In the late 1960s there was considerable interest in developing a mechanical structure that replicated the acoustic performance of a human ear. At the same time I was in the planning stages, Josef Zwislocki developed the Zwislocki Coupler at Syracuse University. He had conducted considerable research with this device and had good supporting data. The folks at IRPI took a look at his coupler, and liked what they saw. They made some minor changes to make sure it was stable and reproducible, and the coupler, called the DB-100, became part of my design.
11 Weren't those early years pretty exciting for you?
Well, sort of, but some of it wasn't so much fun. You would think the world of hearing aid measurement would have been delighted to have someone like me. But, when I first appeared in 1972, a few “scientists” were a little apprehensive about my measurements, so in the next couple years I had to put up with a lot of poking, prodding, and measuring. There probably was not one body part that was not subjected to some criticism.
By far the best part of my life in the 1970s was the people I met. Do you know where I went when I left Knowles? They drove me over to the auditory research laboratory at Northwestern University to work with Raymond Carhart! Once I got there, they put me on a specially designed rotating stand. How cool is that? Rotating in the same room as the father of audiology.
The connection here of course, other than the proximity, was that Dr. Carhart was friends with Hugh Knowles, and over the years both of them had been very involved in hearing aid standards, and served on numerous committees together.
12 Where to next after your visit with Carhart?
As you might have heard, the VA was very interested in me. They routinely conducted a formalized electroacoustic evaluation of commercially available hearing aids, and they were one of the first groups to encourage and promote more realistic hearing aid testing. In particular, they were interested in predicting “real-ear” gain.
Another area of interest was that back in the early 1970s the military and the VA were doing many “open fittings.” The traditional 2-cc coupler measures simply don't tell the whole story (or at least not the correct story). I know, some of you younger readers think that open fittings are something new, but, trust me, people were sticking open earmolds (or #13 tubing only) in my ears and making measurements over 30 years ago!
I remember being at a couple of VA facilities, but the one where I had the most fun was Don Causey's Biocommunications Laboratory at the University of Maryland, which was affiliated with the Washington DC VA. They tended to do a lot of clinically relevant research, which I liked because that went back to the fundamental reason that Hugh Knowles thought I should be developed in the first place. Do you know that at his opening speech at my 1976 “coming out” party in Washington, Hugh spent as much time talking about helping the hearing-impaired as talking about me?
13 What conference was that?
Sorry, I got a bit carried away there for a moment. Let me get back to my VA experience. The hands-down highlight was meeting a woman named Lucille Beck, who goes by the name of “Lu,” I think. At the time she was PhD student, but I've heard that since then she has become quite famous. Consider that up until that time, I had spent most of my life with male engineers, so hanging out with Lu was quite a treat. I regret to say that I don't see her much anymore, but, I still have the University of Maryland t-shirt she gave me. She did some great studies with me; in fact, one of them is published in my book.
14 Your book!?
Hmm. I thought you all knew about this book. It was published in 1978 by Knowles, and edited by Mahlon Burkhard. My picture takes up most of the front cover, and I'd like to say that not many in our profession can make that claim! I've heard that some of you simply call it “The Green Book,” although I'd like to go on record as saying that I had nothing to do with picking out that shade of green!
Well anyway, the story of the book goes back to your earlier question about the Washington, DC, conference, because the book really is a proceeding of a couple of conferences. There are about 20 chapters in the book, taken from talks at these conferences.
That year, 1976, was a crazy one for me. In addition to being subjected to all kinds of research at numerous sites, there was a conference in my honor in Zurich in March, and another for me in Washington in April. Most all the biggies in hearing aid electroacoustic assessment were at one or both of these conferences. In fact, here's something interesting. At the Washington conference, attended by about 40 people, I met a bunch of audiologists in their 20s who were basically nobodies at the time: Jeff Danhauer, David Wark, Robyn Cox, Chris Schweitzer, and Jerry Punch, for example. And you think I don't have influence?
15 No, I never said that. I'd be the first to admit you've hung around with classy people? But what about this Mead Killion guy?
Wow. What can I say about Mead? For starters, let me say that few people have given me as much respect as he has. There were times when he defended me even when others said I was wrong. And, as most of you know, Mead and I have spent a lot of time together. Some say we have even started to look alike, but that of course would depend on my neck rings.
Mead was pretty much there from the beginning, so here's an interesting story about him you may never had heard before. When the folks at Knowles starting doing all these hearing aid measures on me, there was a lot of discussion concerning what my measurements of gain should be called. They needed a term that would clearly differentiate my measures from those of a 2-cc coupler. While they were indeed in situ, that term wasn't appropriate to describe my gain measures, as you could do several in situ measures with me other than gain.
So, they first considered referring to my gain measures as orthotelephonic. This was a term first used in the 1930s in telephone communication research. However, it wasn't quite right for me, as it didn't include the effects of head and torso diffraction—my specialty! Another term suggested was “insertion gain,” which was a term commonly used in communications engineering and was already contained in an IEEE standard. The term “functional gain” was also being tossed around, although it seemed best to reserve that for behavioral measures.
Well, about this time Mead talked to a linguist friend, and they came up with this new ancient Greek word “etymotic.” It combines, etym, meaning true or real in Greek, and otic meaning ear. Well as you know, the term “insertion gain” is the most widely used today, but my buddy Mead has done okay with the term Etymotic!
16 Are you satisfied with the contributions you've made over the years?
Let's see. Thirty-five years ago, before I was born, you all were using 2-cc coupler measures to describe hearing aid performance, even though everyone agreed this was not a good indication of real-ear performance. And what measurements are most commonly used today? Sometimes I wonder if I have had any impact at all.
17 Maybe your measurements aren't mainstream, but what about your contributions to R&D?
You probably should ask the people who have worked with me, but, yes, I'd like to think I've contributed significantly to hearing aid design over the years.
As you know, in the past 10 years there has been a lot of interest in directional technology. Probably without me, today's directional products wouldn't be designed as well as they are. And I guess, indirectly, my measurements are reaching the masses, as some manufacturers use me to determine the CORFIGs they use in their software to simulate real-ear gain.
And, in the last couple years I've been pretty busy helping with the development and design of open fittings. So, to answer your question, I'm not really satisfied, but I do think I've made a difference, maybe even a difference that can be appreciated by the hearing aid user.
18 One of your developers, Mahlon Burkhard, published an article about you titled “Non-hearing aid uses of the KEMAR manikin.” Care to comment on that?
19 So getting back to your new home in Denmark. Is anything about you going to change?
Well, as far as I know, I'm keeping my same name. The most noticeable change is that I'm going to have a new coupler.
Gunnar Rasmussen of G.R.A.S. was responsible for developing the IEC 711 coupler, so it's only logical that I'll be wearing an IEC coupler from now on. It's a good fit. I certainly enjoyed my time with the Zwislocki coupler, but the IEC seemed better for me now that I'm a European.
20 Well, my friend, the KEMAR, enjoy yourself in Europe. Any thoughts on how you'd like to be remembered for all those years in the States?
As you know, I'm primarily a lab rat, and I spent most of my time in the U.S. engaged in research or product development (or just…sitting). I guess I'd like all you Americans to remember me for my even temper, my objectivity, and my integrity. I can honestly say that while working with over 100 research audiologists in the past 35 years, I never got upset, never once leaned forward to improve a HINT score, turned my head to enhance a DI measure, or inflated a COSI or APHAB rating just because I liked the researcher.
I hope you all remember me for this, and I'm looking forward to seeing you all soon. And don't forget about me when you conduct those cocktail party noise recordings!
One nice thing about working with hearing aids is that, relatively speaking, there aren't too many of us, and most of us stay with the profession for a career. That means if you stick around long enough, eventually you'll have quite a few “old friends” or, at the least, “old acquaintances.” If you become immersed in all this, you just might find that your hearing aid friends outnumber your social friends—or they become your social friends.
While The Hearing Journal certainly does not discourage advertising, my lead-in paragraph was not a “Dr. Phil” advertorial; just my way of introducing one of my oldest audiologic friends, who just happens to be the guest author of this month's Page Ten. I'm talking about our colleague who goes by the most famous acronym in audiology. We call him KEMAR, which is derived from his full moniker, the Knowles Electronics Manikin for Acoustic Research.
I first met the KEMAR in the fall of 1974 when I traveled from the University of Denver to the Vicon Hearing Aid Laboratories in Colorado Springs, to have my first listening experience in an anechoic chamber, thanks to a tour arranged by Jim Nunley. As usual, KEMAR was reserved, sat on his stand almost motionless, and quietly ignored the rowdy bunch of PhD students who made jokes about him.
It was a year later when we met again that I really started to get to know the KEMAR, and appreciate KEMAR's contributions to our profession. Directional hearing aids were a hot topic in 1975, and I was back spending many days and nights in that same anechoic chamber in Colorado Springs to make some measurements. No jokes this time. I knew that without KEMAR, my directional hearing aid research wouldn't hold water, and the ASHA paper I was submitting for presentation would be rejected. KEMAR (of course) cooperated, and we've been friends ever since.
As with many close friends, I don't spend as much time with KEMAR as I should, or would like to, and sometimes we go months without seeing each other. We often joke that I sometimes don't visit when KEMAR is down the hall, yet we then run into each other in Europe, Asia, or Australia. I'm pleased that the KEMAR has agreed to write this Page Ten, and I hope that all of you will appreciate the contributions that our colleague has made over the past 35 years. Remember, sometimes your hearing aid colleagues become your social friends!