Frederick Hendrick Fisher, an ingenious experimentalist in ocean acoustics, died unexpectedly on 4 May 2005 in San Diego, California, following a stroke. From laboratory studies of sound absorption to at-sea observations of the details of sound propagation, Fred had made notable contributions to our understanding of underwater acoustics.
Fred was born in Aberdeen, Washington, on 30 December 1926. After graduating from high school, he joined the US Naval Reserve and was admitted to the US Naval Academy in 1945. In 1946 he transferred to the University of Washington, where he received his AB in physics in 1949. Continuing as a graduate student at UW, he became interested in physical acoustics, which had become an active field of research after World War II. During the war, the absorption of sound in seawater was found to be considerably greater than expected; in the late 1940s, physicists at UCLA and at the university’s Marine Physical Laboratory (MPL, now part of the Scripps Institution of Oceanography) in San Diego had isolated the presence of magnesium sulfate as the cause. Eager to understand the details of this phenomenon, Fred joined Leonard Liebermann’s research group at MPL in 1955. Fred devised methods for studying the properties of magnesium sulfate solutions at high pressure and completed his University of Washington PhD in physics in 1957 under Liebermann’s supervision.
Following a year as a research fellow with Frederick (Ted) Hunt’s underwater acoustics group at Harvard University and chemist Benton Owen at Yale University, Fred joined the MPL research staff. In addition to continuing his laboratory research on magnesium sulfate, he began investigating sound propagation at sea—in particular, the accuracy with which sound could be used to determine the direction to a distant target. After conducting initial experiments using a US Navy submarine, he realized that a special platform would be required to support this work. Discussions of how best to make the necessary measurements led Fred and one of us (Spiess), stimulated by a comment by Woods Hole Oceanographic Institution’s Allyn Vine about turning a submarine on end, to the concept of the floating instrument platform (FLIP)—a manned craft 110 meters long that could easily be towed to an open ocean research site where tanks could be flooded and the ship upended to provide a research platform with 90-meter draft. The platform is not only very stable relative to ocean surface waves, but its underwater structure allows hydrophones and other sensors to be mounted at positions accurately known in relation to the exposed, above-water laboratory structure.
Bringing the FLIP concept to reality involved a number of challenges; two in particular resulted in new approaches. First was the concept of shaping the hull to minimize heave response. Philip Rudnick did the theoretical design and Fred, in parallel, did tank experiments with models. The more challenging aspect was understanding the dynamics of flipping from horizontal to vertical and back again. Fred took this on and, with the MPL shop, built a variety of 10-meter-long models and flipped them in San Diego Bay. This fun learning period had the eventual payoff of translating the models, with the help of naval architect Lawrence Glosten, into the full-size version, which flipped for the first time in Puget Sound in 1962.
In addition to supporting Fred’s research for more than three decades, FLIP was and is still used today by other acousticians, physical oceanographers, and atmospheric scientists. After carrying out the bearing-accuracy experiments that were the original goal (and that motivated the US Navy to fund the construction), Fred devised vertical hydrophone arrays that capitalized on FLIP’s stability and could be deployed below to study the vertical directionality of ambient noise and to sample the entire water column for studying sound transmission.
For Fred and others, FLIP’s stability at sea provided a personal advantage. Fred’s seasickness was substantially mitigated once FLIP was vertical and it was time to deploy equipment and collect data.
Fred was not only an ingenious experimentalist in the laboratory and at sea, but he also enjoyed being with people and helping them work together. He was an outstanding tennis competitor, and shared the NCAA doubles championship in 1949 while at the University of Washington.
A central figure in the underwater acoustics community, Fred served in many roles, including president of the Acoustical Society of America (ASA) in 1983–84. Most recently, Fred was involved in a rather complex effort to declassify and ultimately publish scientific documents produced during the cold war that were related to the US Navy’s fundamental efforts in undersea warfare.
We will all recall his many contributions to our understanding of ocean acoustics but, even more, his cheerful, friendly approach to life—embodied in his ever-present garish aloha shirts. Fittingly, ASA will honor his memory at its 2006 meeting in Hawaii where all his friends and colleagues can pay tribute and say, “Aloha, Fred.”
