Hallowell Davis was born in New York City on August 31, 1896. He studied at Harvard University, receiving a B.A. there in 1918 and an M.D. in 1922. Davis's interest in electrophysiology developed while doing post-graduate research in England under Lord Adrian. In 1923, Hallowell Davis joined the Department of Physiology at the Harvard Medical School. His research concentrated on the electrophysiology of nerves. He became associated with the informal group of scientists known as "axonologists," which also included Joseph Erlanger, Herbert Gasser, and others of WUSM. In the 1930s Davis began concentrating on problems relating to hearing, but was also active in research on electrical activity in the brain. He contributed to the development of one of the first ink-writing electroencephalographs. During World War II he did vital war-related research on human tolerance to loud sounds and on the development of hearing aids.
Hearing aid research brought Davis into frequent contact with Central Institute for the Deaf, which was a subcontractor to a Harvard project. In 1946 he accepted an offer to establish a Research Department at CID and also to join the WUSM Departments of Physiology and Otolaryngology.
Among his first major projects in St. Louis was measurement of effectiveness of fenestration operations pioneered by Theodore Walsh. Davis's use of speech in these hearing tests was the beginning of speech audiometry. He became a leading figure in the development of the first American standards for audiometers and the adoption of the international zero reference level as part of that standard. He continued research under several contracts with the U.S. Armed Forces, contributing to work in ultrasonics, mechanical shock, and other areas. In the 1960s he was a member of the National Research Council's Committee on SST (super-sonic transport) and Sonic Boom.
Hallowell Davis retired officially in 1965, but remained active as CID Director of Research Emeritus and Professor Emeritus of Otolaryngology. In 1976 he was awarded the National Medal of Science by President Gerald R. Ford. Davis died in 1992.