Sound pressure levels, frequency spectrum, and jet velocity pro-files are presented for an engine-afterburner combination at various values of afterburner fuel-air ratio. At the high fuel-air ratios, severe low-frequency resonance was encountered which represented more than half the total energy in the sound spectrum. At similar thrust con¬ditions, lower sound pressure levels were obtained from a current fighter aircraft with a different afterburner configuration. The lower sound pressure levels are attributed to resonance-free afterburner operation and thereby indicate the importance of acoustic considerations in after¬burner design.
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