Prof. Mihailo Jovanovic and his collaborators from the Department of Aerospace Engineering and Mechanics, Prof. Joseph Nichols and PhD student Jinah Jeun, have developed a new approach to studying how noise is produced by turbulence in aircraft engine exhausts. The paper titled Input-output analysis of high-speed axisymmetric isothermal jet noise uses techniques from electrical engineering and control theory to discover new coherent modes – parts of the fluid that flow in predictable patterns – associated with the dynamics of high-speed jets. The findings reported in Physics of Fluids (vol. 28, no. 4, April 2016) help explain why jets are so loud and could lead to new approaches to bringing down the noise levels produced by jet engines.