Karl Uno Ingard

Karl Uno Ingard (known generally as K. Uno Ingard), a physicist who worked extensively in the field of acoustics, but who also worked in plasma physics, fluid mechanics, and magnetohydrodynamics, passed away, at the age of 93, on 21 August 2014 in Kittery Point, Maine. He was a member of the Physics Department at MIT from 1952 to 1991.

Ingard was born in Gothenburg, Sweden, on February 24, 1921, of parents Karl Oscar Ingard and Anna Elisabeth Ingard. He graduated from the Tekniska Gymnasiet in Gothenburg, entered Chalmers Institute of Technology in 1940, and graduated as Electrical Engineer in 1944, receiving Chalmer’s John Ericsson Medal (presented annually to the graduate with the highest academic achievement). Following his graduation, he continued at Chalmers, working toward the degree of Technologie Licentiate (a postgraduate degree that may be regarded as an academic step halfway between a master’s degree and a doctorate) .

Throughout his undergraduate and graduate years at Chalmers, Ingard held a succession of part-time positions, including work with an electrical consulting firm in Gothenburg, teaching electrical engineering at the Tekniska Gymnasiet, serving at Chalmers as a research assistant, teaching fellow, and as a lecturer. His principal mentor was Olof Rydbeck, who had a doctorate in applied physics from Harvard and who later achieved considerable renown for work in radar astronomy. Although having acquired considerable experimentally-relevant skills from his father (who was a machinist), Ingard was inclined toward theory, but through Rydbeck, he was put on experimental projects as well, and his interests broadened to a combination of both experiments and theory. During the time of Ingard’s studies at Chalmers, Per Bruel (who had come to Sweden from Denmark during WWII ) was employed by Chalmers and tasked with setting up an acoustics laboratory. With the encouragement of Rydbeck, Ingard was engaged to work within this laboratory, and it was this assignment and the work he did in the acoustics laboratory that initiated Ingard’s life-long interest in acoustics.

Ingard’s graduate studies were interrupted briefly in 1945-1946 with service with the Swedish military, this being spent at the National Electronics Laboratory in Stockholm. Not too long after Ingard’s return to Chalmers, Per Bruel returned to Denmark (where he co-founded the firm of Bruel and Kjaer), and Ingard became Director of the Chalmer’s Acoustics Laboratory. (One outcome of Ingard’s work in acoustics at Chalmers during this period was his invention of the graphic level recorder, which was later commercially produced by Bruel and Kjaer.) Ingard continued on with his studies toward the Licentiate, which he received in 1948.

Igard’s position as Director of the Chalmer’s Acoustics Laboratory was an important position and entailed a long -term commitment to Chalmers. However, he was desirous to receive a high-quality advanced-graduate-level education and decided to try to pursue a doctorate at MIT. He was attracted to MIT partly because of two books by Philip McCord Morse and partly because, as an aftermath of WWII research activities, MIT had established a relatively large research laboratory in acoustics. One of the books by Morse was his Vibration and Sound, and Ingard had actually solved all of the many problems in the book during his time at Chalmers and with the National Electronics Laboratory. (Solving problems was one of Ingard’s life-long “hobbies,” and he later recounted that he regularly worked through all of the problems in the textbooks that he used during his gymnasium and college studies.)

Consequently, Ingard enlisted a colleague (Stig Ingemansson) from Stockholm to take over the Acoustics Laboratory, received a two-year leave of absence from Chalmers, and began graduate studies in the Department of Physics at MIT in the fall of 1948, traveling to the United States on the Queen Mary with his recent bride Doris. His first year at MIT was very stressful because of a long illness caused by a head-injury a few weeks before his departure. Nevertheless, with a characteristic determination and fortitude, Ingard performed spectacularly during the next two years. Although Morse had moved on to interests other than acoustics, Ingard struck up what was to be a life-long close acquaintance with Morse -- this was probably initiated by his pointing out to Morse various errors in Vibration and Sound. Morse was so impressed that he enlisted Ingard to go through and critique the extensive notes and manuscripts of what was eventually to become the two-volume treatise, Methods of Theoretical Physics, which Morse coauthored with Herman Feshbach. (An acknowledgment to Ingard appears in the preface of the fist volume.)

Ingard’s doctoral thesis, “Scattering and absorption by acoustics resonators,” was primarily devoted to experiment and was done under the supervision of Richard H. Bolt, who was then the director of the MIT Acoustics Laboratory. However, there are extensive references to theory throughout the thesis and a strong acknowledgement to Morse. The thesis also acknowledged Leo Beranek for “inspiring discussions.”

At the end of his doctorate work, Ingard was offered a position as an Assistant Proressor at MIT. He asked that the offer be deferred for a year, as he had an obligation to return to Chalmers and teach there. This he did, and he worked at Chalmers for another year, but then returned to MIT in the fall of 1952 as an Assistant Professor of Physics. Except for two sabbatical stints, in Stockholm and Berlin, he remained on the MIT faculty for 39 years until he retired in 1991, at the age of 70. He rose rapidly through the academic ranks, becoming an Associate Professor in 1956 and a Professor in 1966. Although acoustics was strong in the Physics Department during Ingard’s initial years at MIT, Bolt and Beranek left in the later fifties to organize their own consulting firm, and Ingard became the only member of the MIT Physics Department active in acoustics. The MIT Acoustics Laboratory dwindled down to become a shadow of its former self. Acoustics was nevertheless a popular topic among physics students, so Ingard attracted a large number of students over the years. In 1971, Ingard began a joint appointment with the MIT Department of Aeronautics and Astronautics with the additional title of Professor of Aeronautics and Astronautics, and this association gave new vigor to Ingard’s research activities in acoustics.

Ingard’s extensive research achievements are extremely varied and difficult to summarize in a short account, but many of his numerous papers have been extensively cited through the years and have influenced the research of many others. It is perhaps fair to say that Ingard achieved an insight in engineering acoustics and physics-related acoustics greater than any of his contemporaries.

At MIT, his classroom teaching was at first that of teaching basic undergraduate courses in physics – he, for example, taught for many years the basic first course in physics, a full-year sequence that was taught to all MIT undergraduates. Ingard brought a new vigor to the course and illustrated his lectures with many provocative demonstrations. This culminated in a textbook, Introduction to Mechanics, Matter, and Waves (Addison-Wesley, 1960), which was co-authored by his colleague William Kraushaar.

An undergraduate thesis was required of all physics students at MIT and the intrinsic appeal and breadth of Ingard’s research interests, along with the high regard for his teaching, led to Ingard’s directing a large number of undergraduate theses. (The MIT libraries site lists a total of 98 theses supervised by Ingard, but the list is demonstrably incomplete – apparently, the archiving of theses was not done as copiously during Ingard’s earlier years on the faculty. In his encomium written on the occasion of Ingard’s receiving the ASA Gold Medal, George Maling, who was one of Ingard’s earlier students, estimated the total number to be of the order of 150.) Many of the students who wrote bachelor’s theses with Ingard went on to become prominent in acoustics: examples include Peter Rogers and Emmanuel Papadakis, both of whom won the ASA’s Biennial Award (now the R. Bruce Lindsay Award).

The list of names of persons who wrote doctoral theses under Ingard’s supervision is long and includes many eminent names; a possibly incomplete list (36 names) includes James F. Abbott (1991), John M. Andres (1953), L. Wallace Dean, III (1960), Ira Dyer (1954), Paul A. Fleury (1965), Peter A. Franken (1956), Anthony G. Galaitsis (1972), Kenneth W. Gentle (1966), Peter Gottlieb (1959), Hisayuki Handa (1974), Robert H. Katyl (1968), Charles Krischer (1969), George L. Lamb (1956), Ping Lee (1976), Richard H. Lyon (1955), Augustine A. Maduemezia (1965), George C. Maling, Jr. (1963), Wallace M. Manheimer (1967), Charles F. McMillan (1983), Michael A. Martinelli (1965), Gene Mazenko (1971), Paul A. Montgomery (1971), David H. Munro (1980), William P. Patrick (1979), David C. Pridmore-Brown (1954) , James A, Ross (1966), Helmuth M. Schulz (1967), Vijay K. Singhal (1976), George P. Succi (1977), Alfred A. Thiele (1965), James H. Turner (1964), Stephen D. Weiner (1965), Richard C. Williamson (1965), Helbert L. Willke (1963), James M. Witting (1964), and Jeffrey A Zimmer (1983). Those who went on to achieve special eminence in the Acoustical Society include Ira Dyer (President, 1997-87; Gold Medal, 1996), Richard H. Lyon (President, 1993-94 ; Gold Medal, 2003, and George Maling (Silver Medal in Noise, 1992).

Partly because of his many research accomplishments, Uno Ingard received many awards over the years; these included the ASA Biennial Award (1954), Gold Medal (1998), Rayleigh Medal of the UK Institute of Acoustics (1981), ASME Per Bruel Gold Medal for Noise Control and Acoustics (1989), Honorary Doctorate of Engineering, Chalmers University of Technology (1979), John Ericsson Medal of the American Society of Swedish Engineers (1972), election to the US National Academy of Engineering (1980), and the INCE Education Award (1995). Ingard served on the ASA Executive Council (1970-1973) and was President of the Institute of Noise Control Engineering (1973).

Ingard is widely known to the acoustics community because of his co-authorship, with P. M. Morse, of the treatise Theoretical Acoustics (McGraw-Hill, 1968). The first 600 pages of this book are for the most part a revision of Vibration and Sound, but the last 300 pages are quite different and are believed to be largely written by Ingard; the subject matter of the last five chapters contains topics on which, over the years, Ingard had studied in depth and on which he had done research.

In addition to his research, Ingard carried out extensive consulting activities in noise control, the projects generally being quite intensive. Dupont, Pratt and Whitney, United Technologies, Industrial Acoustics Company, Stahl Laval Turbine AB, and Mitco Corporation are among the companies that engaged his services.

In his later years, especially after his retirement, Ingard spent considerable time writing books dealing with topics on which he had worked over the years, with an expressed desire to pass on what he had learned to others. These include Fundamentals of Waves and Oscillations (Cambridge, 1988), Notes on Acoustics (Infinity Science Press, 2008), and Notes on Sound Absorption Technology (Noise Control Foundation, 1994).

Ingard’s legacy in acoustics is huge. His many papers and books will long continue to be consulted and cited, and those who knew him will long cherish their memories of conversations they had with him and of the excellent lectures they heard him give. [The portrait accompanying this account was painted by Doris Ingard, Uno’s wife.]

Allan