UC, Navy design could muffle roar of fighter jets

https://www.uc.edu/news/articles/2021/09/uc-engineers-quieter-jet-engines-for-fighter-planes.html

"interior of the nozzles features triangular fins like rows of shark teeth... change the behavior of the flow coming out of the engine with minimal effect on its performance... could reduce engine noise by between 5 and 8 decibels... decibels are measured in a logarithmic scale... By suppressing the noise, you are helping the crew but also helping the longevity of the airplane itself"

Related:

A New Material Can Block Out 94% of Noise. Even in a Jet Engine

https://interestingengineering.com/new-material-can-block-out-94-of-noise-even-in-a-jet-engine

Making the World a Lot Quieter

https://www.bu.edu/articles/2019/making-the-world-a-lot-quieter/