Alan Selfridge performed pioneering work on ultrasonic array design and optimization at the E. L. Ginzton Laboratory at Stanford under the supervision of Prof. G. S. Kino. Shortly after completing his Ph.D. Alan collected an immense and valuable set of acoustic material parameters that was later published in the IEEE Trans. Sonics and Ultrasonics (later Trans. UFFC). The data in this article was developed over successive years to become the single most valuable collection of material parameter information for the ultrasonic transducer design community. Alan’s table of acoustic material parameters forms the foundation of the table of acoustic material parameters to be published on the UFFC website. Alan Robert Selfridge was born Feb. 27, 1954 in Midland, Michigan, just twenty minutes after his fraternal twin brother Rohn. In 1958 the family moved to Citrus Heights, Calif. where Alan’s father Robert worked on solid fuel rocket propellants for Aerojet General. Alan graduated from San Juan High School in 1972, and subsequently from UC Davis with an emphasis on pre-med subjects. In 1976 Alan began his doctoral studies in electrical engineering at Stanford, with an emphasis on ultrasonic physics. He received a Ph.D. in 1983 and began his consulting business, Ultrasonic Devices Inc., from his home in Palo Alto. In 1983, Alan bought a beautiful piece of land in the redwoods of the Santa Cruz mountains, with an old house and barn on the property. He also purchased Specialty Engineering Associates (SEA,) then located in Milpitas, Calif. to complement and expand his consulting business. In 1988, Alan and Peggy Johnson began their loving relationship, and their daughter Julia Maria Selfridge was born on May 9, 1989. Alan and family moved to the mountain land shortly before the birth of Aaron Rohn Selfridge on June 8, 1993. Alan and Peggy were married on August 24, 1996 at the Skyland Church. Peter Goetz, his good friend, joined SEA as Alan’s business partner in 1995. In the summer of 1996, Alan bought a large warehouse in Soquel, Calif., into which the company moved late in 1996. Alan was a man of incredible energy. His perfect workday began with a morning spent in his mountain studio programming, consulting, developing, and testing acoustic devices for medical and other industrial applications. He held a number of patents on various ultrasonic concepts, and his work has impacted people throughout the world. Professionally he was widely noted for his brililance and his technical achievements in the physics of ultrasonic transducer design and measurement, as well as his folksy nature and his ability to make the difficult seem easy.
He loved to spend afternoons working on the property, putting in trails, managing his extensive water system, building a spiral staircase up a redwood tree, and running with Peggy. Alan loved the mountain and seldom had a desire to leave it. Because he worked primarily at home, he was present and supportive to Peggy, Julia, and Aaron to an extraordinary extent. We will miss him.