Westley Farnsworth Curtis, 77, a retired Navy Department physicist who specialized in underwater sound research and who helped develop sonar during World War II, died Jan. 4 at Suburban Hospital after a heart attack. He lived in Bethesda.

Mr. Curtis began his career at the Naval Research Laboratory here in 1928 doing research in radio measurement. He later worked in microwave production and reception. From 1939 to 1953, he headed the underwater sound research section at the David Taylor Model Basin, now the David Taylor Naval Research and Development Center, in Carderock. During that time, he helped in the research and development of sonar, or sound navigation and ranging, which came into practical use during World War II.

Before retiring in 1969, Mr. Curtis served as acting head of the Acoustical Vibration Laboratory at the David Taylor Model Basin.

He received the Navy Department's Superior Civilian Service Award in 1964.

Born in Greeley, Colo., he graduated with a bachelor's degree in physics from Colorado College in 1928. He earned masters' degrees from George Washington University in 1932 and the University of Maryland in 1945.

After his government retirement, Mr. Curtis was an energy consultant.

He was a cofounder of the D.C. Energy Task Force and a former president of the Cabin John Park Volunteer Fire Board.

Mr. Curtis wrote numerous scientific publications in his field and held patents on several inventions. His memberships included the American Physical Society, the Federation of American Scientists and the Washington Philosophical Society. He was a fellow of the Acoustical Society of America and an associate member of the Naval Institute.

Survivors include his wife, Thelma B., of Bethesda; a son, Richard F., of Tucson, Ariz.; a sister, Frances Pond of Lemon Grove, Calif., and two grandchildren.

The family suggests that expressions of sympathy be in the form of contributions in his name to All Souls Unitarian Church in Washington.