Chevrons Bring Quiet to Jet Engines at 0.5% Thrust Penalty

A NASA-developed technology called chevrons has been used by Boeing to reduce jet engine noise, but not Airbus. The distinctive sawtooth edges on some Boeing engine nacelles are a result of this innovation.

The technology was developed through research into how hot exhaust from a jet engine mixes with surrounding air. This mixing process creates turbulent structures that contribute to noise.

NASA's laboratory work showed that chevrons could reduce thrust by only 0.25 percent, which was considered negligible compared to the acoustic benefit. The technology was later tested on a modified Learjet 25 and confirmed to produce meaningful noise reductions.