Early years of the parametric array—An anecdotal history

This review covers the period from 1960 to about the mid‐1970s. Westervelt presented his theory of the parametric array at the June 1960 Acoustical Society Meeting, held at Brown Univ. In the same session, Bellin and Beyer reported experimental confirmation, primarily for the array in water. Despite the tantalizing properties of the parametric array—narrow low‐frequency beam produced with a small source, absence of sidelobes, and potentially broadband operation—the acoustical community at first paid little attention. Berktay woke us up with a series of papers in the mid‐to‐late 1960s on possible applications. Interest in underwater parametric arrays then exploded, including attempts to make parametric receiving arrays practical. Definitive experimental confirmation of the parametric array in air was finally reported in 1973. However, practical applications of the airborne array did not appear until many years later.