Dr. William L. Siegmann

Siegmann, Dr. William L.
EAST GREENBUSH - Dr. William L. Siegmann, 82, passed away peacefully on Friday, December 5, 2025, at St. Peter's Hospital after a protracted illness.
Born in Pittsburgh, Bill was the only son of the late William A. and Lois (Marloff) Siegmann. A gifted scholar, he earned his B.S., M.S., and Ph.D. in Mathematics from the Massachusetts Institute of Technology (MIT). His doctoral thesis, Time Dependent Motions in Rotating Stratified Fluids, became the foundation for his prolific research career in the field of acoustic vibrations and underwater sound propagations largely with the United States's Office of Naval Research (ONR) but also with the NSF, NASA Langley Research Center and the Army Atmospheric Sciences Laboratory. Bill joined the Rensselaer Polytechnic Institute (RPI) faculty in 1970, marking the beginning of a distinguished career in teaching and academic leadership. Over his 55-year career at RPI, he served as Professor of Applied Mathematics (Emeritus) and Associate Dean of Science. Following retirement, he continued to support RPI students as Ombudsman for the Office of Graduate Education. He taught thousands of RPI students and was known affectionately as the "candy man" for his penchant of tossing candy to students who answered correctly. He mentored nearly 40 doctoral students and many more master's candidates; his students recalled him as a gentleman scholar, more than a technical advisor. Supporting his family members and students to achieve their goals and dreams was his life's work.
Over his career, Bill authored more than 132 publications. He was an Associate Editor for the Journal of the Acoustical Society of America. Bill valued his lifelong friendships with colleagues; and if asked, he counted his numerous graduate students as his "mathematical children," and took great pride in their achievements.
Beyond academia, Bill's civic responsibility encompassed serving on both the Town of East Greenbush Planning Board and the Board of Assessment. He was a member of the Greenbush Reformed Church.
Bill's intellectual passion for underwater acoustics carried into his family life, where annual vacations to Long Beach Island became cherished traditions. The family fondly remembers drives to New Jersey with Bruce Springsteen playing, his sonorous voice reading aloud Tolkien and The Night Before Christmas, his enthusiasm for discussing WWII history, his competitive spirit in the group Solitarie and 500 card games, and how joyfully he called out Bingo numbers. He was endlessly curious. Every conversation with him invariably included a line of questioning, and often with the exhortation to "Let's look it up!" Bill is survived by his beloved wife of 60 years, Nancy Siegmann; his seven children and their spouses, of whom he was immensely proud,: Lisa Siegmann, Sara (Bob) Schuman, Lora (Matt) Werner, Kate (Rick) Robertson, Jonathan (Cassandra) Siegmann, Ruthann (Brian) Rapp, and Andrew (Lindsey) Siegmann; and his 18 adored grandchildren, who lovingly called him "Pops," Heidi (Freddie), Eric, Holly, Will, Ben, Elizabeth, John, Sam, Emma, Sloane, Colin, Morgan, Audrey, Catherine, Ryan, Adeline, Jake, and Natalie.
Relatives and friends are invited to attend calling hours on Friday, December 12, from 4 to 7 p.m., at Rockefeller Funeral Home, 165 Columbia Turnpike, East Greenbush. A public service will be held Saturday, at 10 a.m., at the funeral home, followed by private interment. His family is working with RPI to plan a celebration of Bill's life on campus this spring. The family suggests honoring Bill's memory with a donation supporting his lifelong passion for education at RPI. You may do so by visiting https://giving.rpi.edu/supportscience, selecting Mathematical Sciences Excellence Fund,"; selecting "This is a memorial or tribute gift"; and filling in "Bill Siegmann."