Overview of Combustion Noise

Combustion noise was discussed as early as 1802 in a technical note on singing flames. Occasional papers followed this early work up to about 1950, when jet propulsion spurred interest. Since then there has been a continual broadening of the areas of interest: Now the phenomena related to combustion noise are considered in a host of specific uses of combustion. This review is based on the authors' observations of nonpropulsive combustion in the residential, commercial, and industrial fields, although it is realized that there are many parallels to specific propulsive applications. Three specific areas of combustion noise are discussed in some detail, namely, combustion roar, combustion-driven oscillations, and pulse combustion. Combustion roar, in the absence of acoustic distortion effects, is characterized by a smooth noise spectrum related to the reacting chemistry of the flame and the turbulence level of the combustion region. Combustion-driven oscillations are characterized by a discrete frequency and a feedback cycle to maintain the oscillation. Pulse combustion is the positive application of combustiondriven oscillations. In addition, some other combustion noise phenomena are discussed, such as the interaction with vortex shedding and the combustion amplification of flow phenomena.