Acting Citizen: Fletcher-Munson Curves

By James Knudsen

I imagine it is the experience of most that there are people we get to know when we are children and they are nearing the end of their lives. Our memories of them are formed in a child’s mind and the span of time we get to know them is shorter than most of our other relationships. And when they die, what we are able to learn about them after they’re gone is usually limited. And sometimes, we get a second or third chance to learn more about them.
    When I was born in 1965, all of my great-grandparents had passed way years earlier. And only three of my biological grandparents remained, my maternal grandmother having passed away 15 years earlier at the age of 47. The remaining three ranged in age from 65, my mother’s father, L.D. Cotta, to 71, my father’s father, Vern O. Knudsen. My paternal grandmother split the difference at 67. Nine years later, “Grandpere” Vern would pass away five months after his 80^th birthday. There would be a burial in Provo, Utah, shortly afterwards, which I did not attend. Some weeks later a memorial service followed at the University of California, Los Angeles, and a reception at the family home in Brentwood, of which I have a few memories. And prior to that, my recollections are few and those of a child who knew that his grandfather was a doctor, but not the kind that helps sick people.
    I was 30 years old when I first learned of the significance of Dr. Vern O. Knudsen in the world of physics, and in particular the field of acoustics. A theater assignment required me to learn about and report on The Drottningholm Palace, an 18^th century theater in Stockholm, Sweden. It had been closed following the assassination of King Gustaf III in 1792, and remained closed until 1922. The library at California State University, at Dominguez Hills had in its collection Theater Design, by George Izenour, with contribution by Dr. Vern O. Knudsen. What? As I examined the pages of the eight-pound tome (which can be yours via Amazon for just $624), I found line drawings of theaters with the notation, “design by George Izenour, acoustical consultation, Dr. Vern O. Knudsen.” This was my first exposure to Vern’s influence in the field of acoustics. Izenour and Knudsen collaborated on such well-known spaces as the Grady Gammage Auditorium at Arizona State University, The Marin Veterans’ Memorial Auditorium, and their final joint project, the E.J. Thomas Performing Arts Hall, located on the campus of The University of Akron.
    A decade later, I happened upon some boxes of Vern’s papers at the family home. I contacted the local office of the Acoustical Society of America (ASA), which Vern had helped found in 1929, and arranged to have them picked up by the president of the local chapter. In the course of doing this, I learned of the importance of one Harvey Fletcher. I had met Dr. Fletcher as a child in the 1970’s, and when I mentioned this to my ASA contact during a phone call, the response was, “You met Harvey Fletcher?!!?!?” Imagine meeting a Star Trek fan and telling them you sat in Capt. Kirk’s chair; it was like that. And Dr. Harvey Fletcher provides the bridge to my most recent discovery about my grandfather’s life and work.

Three years ago, while teaching at the College of the Sequoias, in Visalia, California, I took advantage of their policy that allows faculty to attend classes free of charge. I chose Recording Arts I, an introductory course that covers the use of music recording software, microphones, and other devices that allow mere mortals to record music – entire albums in some cases – at home with a computer and a couple of electronic instruments. The textbook for the course is Modern Recording Techniques, by David Miles Huber and Robert E. Runstein. It covers two or three courses on the subject and is used by many departments. It occurred to me that Vern might be mentioned. A quick check of the index revealed no “Knudsen” under “K.” Then I remembered Dr. Fletcher. Harvey Fletcher, like Vern O. Knudsen, was a native of Provo, Utah. He had been Vern’s physics professor at Brigham Young University, having been the first student to receive a doctorate in physics, summa cum laude from the University of Chicago. He is credited with inventing stereophonic sound, the first functional hearing aid, a posthumous technical Grammy Award, and I was told by someone in the know that the telephone would not sound as good as does (did) were it not for the work of Dr. Harvey Fletcher. So, I turned to the letter “F” in my copy of Modern Recording Techniques, and sure enough, “Fletcher-Munson curves” greeted my eyes.
    The Fletcher-Munson curve, also known as the equal-loudness contours, are found on the box of just about any piece of audio equipment one might purchase. What Fletcher and his assistant, Wilden Munson, sought to address is the non-linear fashion in which the human ear perceives sound. Their findings influenced the development of sound recording and reproduction equipment for years to come.
    Wait! You’re thinking, it’s Fletcher-Munson, not Fletcher-Knudsen – where’s the link? Around the same time I was learning about equal-loudness contours, I came across a pair of interviews conducted in 1964 at UCLA. In the first interview, Dr. Vern O. Knudsen interviews his old professor, Dr. Harvey Fletcher. In the second, Dr. Leo Delsasso interviews his old professor, Dr. Vern O. Knudsen. During this second interview, Delsasso recounts watching his brother Lewis “calculate the frequencies and the conditions which are necessary for oscillation with the different types of oscillator circuits.” Lewis Delsasso’s partner in this endeavor, which required yards of butcher paper, was Wilden Munson. You might say Vern is the hyphen in Fletcher-Munson. After learning of my grandfather’s connection to this element of recording technology, I sent my instructor an email with the following photo attached.

Vern O. Knudsen (on the left) & his old professor, Harvey Fletcher

    This would have been the end of the story, but in the process of gathering the information, I learned yet another piece of trivia. As mentioned before, George Izenour was a frequent collaborator of Vern’s. What I did not know of until recently was Izenour’s work with the U.S. Navy during World War II. That Vern had been involved in anti-submarine research was well known in our family. My father, Morris Knudsen, remarked that he “didn’t have a father” during the war years owing to Vern’s long absences conducting research for the U.S. Navy. It is reasonable to assume that the earliest Izenour-Knudsen collaboration occurred while trying figure out how stop the German submarines prowling the North Atlantic.

Copyright © 2022 by James Knudsen