Engineers at the University of Cincinnati are turning down the volume on jet engines. In a bid to tackle the chronic issue of jet noise, which not only impairs the hearing of military service members but can also damage the aircraft, they’re coming up with new engine nozzle designs. The research, backed by the U.S. Office of Naval Research, is seeking a balance between quieting those deafening roars and keeping engine performance unhindered.
Kaurab Gautam, a researcher in the university’s Gas Dynamics and Propulsion Laboratory overseen by UC Distinguished Research Professor Ephraim Gutmark, is at the forefront of this acoustic conundrum. "Jet noise is a big problem," Gautam told the University of Cincinnati. With more than 3.6 million veterans affected by hearing loss and tinnitus because of noise exposure, the stakes are high for finding a solution.
Within the unique confines of anechoic chambers lined with sound-absorbing foam, Gautam conducts experiments on various jet engine nozzle shapes, measuring the cacophony they produce. These chambers are so effective at dampening noise that working in them can be disorienting, a challenge that Gautam seems unfazed by. The research also involves capturing high-speed videos of airflow through the nozzles, which visually demonstrate the turbulence and noise created by different designs. "We have to understand how the nozzle reduces the noise," Gautam explained in a statement obtained by UC News, combining quantitative and qualitative approaches to solve the puzzle.
Gautam’s experimentation has led to exploring over a dozen trapezoidal nozzle designs, resembling those used in advanced fighter jets like the F-22 Raptor. Despite their importance, these shapes can't be too square, or they'll increase a jet’s heat signature — making it an easier target for missiles. "We're measuring the jet flow and capturing the sound," said Gautam in a statement obtained by UC News, who is also recognized by the American Institute of Aeronautics and Astronautics with a 2025 graduate award for his work in propulsion. His prototypes, at the moment constructed from 3D-printed materials suitable for cold air tests, may eventually be printed in metal for high-temperature engine tests.
There's a world of science behind quieting the roar of jets. From signal processing to rapid prototyping, the team at UC is pushing the envelope to ensure the skies become a little friendlier to both service members’ ears and the structural integrity of the aircraft they operate. As for the results of these studies, only time, and perhaps less noise, will tell if these quieter nozzles will take flight in the real world.
