ABSTRACT
The pressure gradient microphone, also known as the velocity microphone, senses sound
pressure at two very closely spaced points corresponding to the front and back of the
diaphragm. The diaphragm is thus driven by the difference, or gradient, between the
two pressures. Its most common form, the dynamic ribbon (diaphragm) microphone, was
developed to a high degree of technical and commercial success by Harry Olson of RCA
during the 1930s and 1940s and dominated the fields of broadcasting and recording in the
United States through the mid-1950s. The BBC Engineering Division in the United
Kingdom was also responsible for significant development of the ribbon, extending its
useful response to 15 kHz at the advent of FM radio transmission in the mid-1950s.
