Acoustics of excited jets—a historical perspective

The idea that a jet may be excited by an external forcing is not new. The first demonstration of a jet responding to external pressure waves occurred in the late 1800s. It was not, however, until the 1950s, with the advent of commercial jet aircraft, that interest in the subject greatly increased. Researchers first used excited jets to study the structure of the jet and attempt to determine the nature of the noise sources. The jet actuators of the time limited the range (size and Mach number) of jets could be excited. As the actuators improved, more realistic jets could be studied. This has led to a better understanding of how jet excitation may be used not only as a research tool, but also as a method to reduce jet noise.