In Memory of Mead C. Killion

We usually only fully appreciate someone we've lost when they're gone. I have followed Mead Killion's many significant contributions to our field of hearing science and their direct benefits to clinical practice, hearing aids and hearing protection that have emerged over the years. This made me acutely aware of his loss, even before he died, following the sale of the company he founded, Etymotic Research, Inc., and saw so many of the innovative products developed by Mead and his first-class team of product development engineers gradually disappear from the scene, leaving an enormous gap. Though there are some companies that are trying to fill the gap, researchers and clinicians who use Etymotic products are trying to restore their ability to do ground-breaking work from other manufacturers.

I first met Mead in the fall of 1981, the year I joined the NU faculty in what is now the Department of Communication Sciences and Disorders. I was in the machine shop in the basement of Frances Searle, busily building sound sources for hearing research in chinchillas. After introducing himself as a student who worked with his graduate advisor Tom Tillman and Peter Dallos, Mead offered some great suggestions on how to improve the design of my sound sources. Mead had considerable experience in acoustics, having worked for Knowles Electronics for more than twenty years. He played a major role in designing the miniature microphones and sound sources and high-quality amplifiers incorporated into hearing aids. He had developed a strong relationship with Hugh Knowles, who supported Mead when he decided to leave Knowles Electronics to found his own company (Etymotic) in 1983, taking with him several innovations that Mead had been developing at Knowles. Our Audiology founder, Dr. Raymond Carhart, was also a friend of Knowles, so it is no wonder that the strong connection with Northwestern led to the decision by the Knowles family to endow our department in what is now the Knowles Hearing Center. The benefits of this endowment to our department have been priceless, fostering ground-breaking research, clinical practice and the support of Audiology students. He supported both PhD and AuD student committees over many years and supplied small equipment items such as noise dosimeters for free.

I saw him give a masterful presentation of hearing conservation to students in the NU Music school, but was also concerned with preserving hearing in extreme noise levels including soldiers in combat and those serving on the flight deck of an aircraft carrier where sound levels can exceed 160 dB SPL. Both of those situations require that personnel not only preserve hearing from noise, but are also able to maintain good communications, including simply understanding commands.

One only needed to pay a visit to Etymotic Research in Elk Grove Village to get a sense of why the company became so incredibly productive. Mead's office had doors that opened into the reception area on one side and into a large common room on the other. Mead's office was smaller than most faculty offices in Frances Searle, not exactly what one would expect for the founder of an important company. In addition to the design and product development engineering team, many of the company's products were built on site and sold, packaged and shipped from the same building. The large, central meeting area had a kitchen and was filled with tables and seats for lunch and informal meetings between anyone working on any aspect of Etymotic products. If a problem was detected, the people directly able to solve it were there in the building and were encouraged to collaborate to find a solution. It was a tightly woven community and the positive result was readily apparent. Mead had confidence in people he employed and placed great trust in them. More than once did I think about what it would be like to work there, with a fantastic array of highly creative people and the machines to build miniature pieces of instrumentation, with abundant expertise in practically anything relating to hearing.

My most intensive interaction with Mead and the Etymotic engineering staff was the development of the ER-10X research probe system. This was by far the most complex piece of equipment Etymotic ever produced. It could deliver more than 90 dB SPL of low-distortion sound over the entire human hearing range, but could also make measurements at ultrasonic frequencies that was well suited to research in small animals. It has been used in many of the top acoustics labs in the world. The probe inserted in the ear canal could be precisely calibrated to allow in-the-ear compensation of eardrum sound levels and also made it possible to present complex acoustic stimuli to the ear. It also had a very low noise microphone that could be used not only to compensate acoustic stimuli, but reliably and repeatedly measure low-level otoacoustic emissions generated by the inner ear hair cells. But there was no limit to the range of applications, including advanced assessments of wide-band middle ear function and measurement of the acoustic reflex at threshold levels around 60 dB SPL. My lab has recently discovered that the strength of the reflex can be more than tripled by prior moderate-intensity sounds, suggesting that the reflex serves primarily to adapt hearing to differing levels of environmental noise.

The ER-10X was partly supported by a contract from the Office of Naval Research in large part to support research in hearing conservation. I served as P.I. with Sumit Dhar, Mead and lead engineer Steve Iseberg as co-investigators. It was a great team. Sumit and I contributed insights gained from our work in humans, while I brought experience from work in laboratory animals. Steve is an incredibly creative engineer who routinely came up with clever solutions to difficult practical problems, including how to miniaturize high performance sound sources and microphones into a small package that would comfortably fit inside an ear-muff hearing protector to make laboratory quality measurements without needing a sound booth. It really was the beginning of the emergence of the next generation of hearing test instruments. During one of our discussions of advanced features that might be incorporated into the probe, Mead interrupted with the question: "Is this going to do anybody any good?". He remained consistent to the meaning of Etymotic – "true to the ear". If a feature wasn't going to contribute in that spirit, then it wasn't needed in a product.

Mead also contributed greatly to the design of the ER-10X from his wealth of knowledge and experience, but among his most important contributions was to consistently support the very expensive development costs. There was never any expectation that Etymotic would make a large profit from making and selling the ER-10X. It was not intended to be mass-produced and sold widely to hearing clinics. It was primarily intended as a powerful tool that researchers could use to extend the state of the art. When I began my career, I never thought that it would ever be possible to do precisely calibrated acoustic experiments in humans as we could do routinely in laboratory animals, but the ER-10X allows us to do exactly that. But following the sale of the research development division of Etymotic Research to Interacoustics, Inc, further development of the ER-10X was cancelled and the probe system was taken off of the market. Support for existing users was also discontinued. The ER-7C probe tube microphone and the ER-10C and ER-10B+ otoacoustic emission probes were also discontinued.

Although Etymotic did not sell integrated measurement systems, several manufacturers used their microphones and probes in their own integrated systems. It also meant that individuals like Steve Neely of Boys Town NRH could develop freeware software that could measure system responses and otoacoustic emissions, only needing a computer with a suitable high quality digital audio interface. It also led others to develop applications in Matlab that could be shared among members of the research community. This represents the perfect balance of the availability of open-source software with relatively inexpensive microphones and probes including the ER-10X made by Etymotic. This is no longer possible, but a few companies are trying to fill the enormous hole left by the loss of Etymotic products. The ER-10X has been available long enough (the one in my lab still works!) for us to learn some of the aspects of equipment performance that were needed to achieve the high point in the state of the art that will be needed in future instruments that will hopefully become standard features of future research labs and clinics.

Sadly, the most significant loss was the driving force provided by Mead Killion, whose knowledge, compassion and advocacy for hearing health will be extremely hard to replace. Looking back over his career, I'm not confident that we ever will.

Jon Siegel

I wrote to Mead when I was an undergraduate looking for master's programs. Although at the time I wasn't planning a PhD, I was already working in a research lab, so I wrote to people whose research interested me. (I didn't, at the time, understand the distinctions between someone employed full-time at Northwestern and someone who had an affiliation.) I wrote to a number of researchers at different institutions. Most of them didn't reply (why would they? I was an unknown undergraduate). But Mead did. I still remember that he wrote me a long encouraging letter and told me that if I came to Northwestern, I should get back in touch with him. I didn't go to Northwestern then, but I did get to meet him many years later as a Northwestern faculty member myself. And I took (sat in on) his hearing aid class and learned more! Even the last few years and long after he retired he would occasionally call my cell phone to share some project idea he'd just thought of, calls I appreciated and enjoyed. I learned from him before I knew him, after I knew him, and still today. He and his creativity and enthusiasm to learn will be terribly missed.

Pam Souza

I will share two memories. But first, Mead was always kind to me and answered all my questions however irrational they were. He told me one time that he would always answer my calls because I was Jon's friend and therefore I must "be OK!"

In one of the many many meetings we had with the Etymotic team during the development of the ER10x, we were locked up in a meeting room for hours trying to decide the location and size of a vent hole that would allow the pressure in a calibration tube to equalize without affecting the acoustics. Mead was not in the room. After a while, he poked his head in and asked what we were doing. Once he heard about the problem we were trying to solve, he simply said "point six mm" and left. I believe the final diameter of the vent hole was pretty close to the number. I may be remembering the number incorrectly.

When I was department chair, I asked Mead to teach a seminar on translating science to commercial products for our PhD students. He invited a series of top notch entrepreneurs from the field including Rodney Perkins. They all came. Rodney flew out from California to spend two hours with the students. On the last day of class, each student pitched a start up based on the science they were pursuing. At the end of the class Mead declared that he had opened a new bank account and already put an initial $10k to support any of these ideas. He told the students that if any one was serious about commercialization he was ready to listen and would fund the startup to a reasonable amount.

Sumit Dhar