Semin Hear 2004; 25(1): 7-16
DOI: 10.1055/s-2004-823043
Copyright © 2004 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York,
NY 10001, USA.The “Missing 6 dB” of Tillman, Johnson, and Olsen Was Found - 30 Years Ago
Michael G. Block1
, Mead C. Killion2
, Tom W. Tillman3
- 1Director of Technical Services, Qualitone, St Louis Park, Minnesota
- 2Etymotic Research, Inc., Elk Grove Village, Illinois; Visiting Professor of Audiology,
Rush University, Chicago, Illinois; Adjunct Professor of Audiology, City University
of New York Graduate School, New York, New York
- 3deceased; former Associate Dean, School of Speech, Northwestern University, Evanston,
Illinois
To Tom Tillman, with Gratitude
When I arrived at Northwestern University as a new doctoral student in the fall of
1971, I was in awe of the fact that I was going to be in what most people then considered
to be the center of audiology. The people I would work with were those who wrote most
of the texts and research I had read. Little did I realize that I would also be in
the midst of a period of transition.The old Speech Annex was being replaced with the new Frances Searle Building to house
the School of Speech. The Northwestern way of connecting pieces of equipment using
coax cable with banana plugs routed at right angles along the edges of the equipment
was giving way to MAC Panel plug boards and plug wires. The use of calculators to
run statistical analyses was giving way to computer punch cards and the SPSS software
package. The system of storing subject information on McBee keysort cards was being
replaced with newly developed computer database systems. The use of transformers to
match different signal sources was being replaced by a new semiconductor called an
operational amplifier. A newly developed pressure pump was changing the way we understood
middle-ear function.I was caught between the tradition of the Northwestern way of doing things and the
emerging technology of computers, new facilities, new electronics, and new diagnostic
tools. Naturally, I was nervous. I had so much to learn but confused about the right
path to follow. Tom Tillman was a source of direction and inspiration for me. He helped
me to see the value in both the traditional and the modern. He taught me to embrace
change without disregarding the past. Tom helped me to understand that to move into
the future we must not lose sight of our past. I will always to be grateful to Tom
for his insight, his ability to analyze a problem and see a solution, and the help
he gave me in finding the path to my eventual graduation in the summer of 1975.Michael G. Block, Ph.D.
Missing Tom Tillman
I've missed Tom; really missed having him answer the phone when I had a knotty academic
or research problem. And I miss the reminder that one of my idols had become one of
my friends.I had called only a few weeks before Tom died when a Ph.D. student discovered that
the way she set the gain on the digital hearing aid she was using could arguably have
been set a better way. She had originally checked it three ways, including the old-fashioned
oscillator-voltmeter method, but its high-frequency gain for dynamic speech sounds
was higher than expected (and higher than might have been optimum). Tom listened to
the account, to her willingness to redo half of her data collection, and said “As
you go along in every research project, you encounter ways that you could have done
it better. But the time comes when you need to stop improving and complete what you
started. I think that is where you are here.” You can imagine her relief (and mine).
The answer was all the more welcome because of Tom's absolute integrity; he would
never have given such an answer to make a student (or advisor) feel better at the
expense of good research.Tom genuinely liked and cared for students. Tom is almost the sole reason I have a
Ph.D. Over 30 years ago, I called Tom about an article he had written with R.M. Johnson
and Wayne Olsen on the “Missing 6 dB.”1 I thought the experimental findings were correct,
but didn't think anything was “missing.” Tom not only wasn't defensive, but invited
me to Northwestern to discuss the article. At the end of that discussion, he enlisted
a graduate student, Michael Block, to carry out the additional experiments we devised
to settle the question. Some eight years later, I decided that my preconceptions about
the type of people who obtain Ph.D.s couldn't be entirely correct, and-with Tom's
encouragement-enrolled at Northwestern where Tom became my Ph.D. advisor.The next time I saw Tom under pressure was when a check on the levels of the recorded
stimuli used in some perceptual masking experiments indicated that the reported “8
dB of perceptual masking” was an artifact of a complicated calibration procedure (not
Tom's). To explain, it turned out that the real-speech masker was ∼8 dB more intense
than the speech-envelope-modulated speech-spectrum noise masker. Tom had been associated
with many of the early perceptual masking findings, and might have been expected to
be defensive. I watched Tom during the meeting as the new findings and calibration
checks were described. He listened intently and at the end said, “We should check
this new finding and, if it holds up, report it so that no one else will make the
same mistake.” Other colleagues expressed concern for their reputations and for that
of Northwestern. Tom always focused on the search for truth; I never saw him flinch
in light of possible personal consequences.After my own dissertation committee had listened to my third Ph.D. proposal and rejected
it as “not interesting” and worse, I wrote a blistering three-page retort, explaining
the committee's abysmal lack of insight. I sent all five copies to Tom to distribute,
gave up on my Ph.D., and went back to work full time. Tom waited quietly for six months,
then invited me over for a visit whereupon he confessed that he had never distributed
my diatribe and wondered if finishing my research (and Ph.D.) wasn't more important
than being right? Tom could be just as gentle when necessary as he could be rigid
as iron when facing poor science or questionable ethics. As a scientist, a writer,
a teacher, and a mentor, Tom had few peers. But mostly I will miss him as a trusted
friend.Mead C. Killion, Ph.D.
