Atmospheric turbulence filter functions derived from high‐fidelity measurements

Abstract

Efforts have been underway to develop filter functions suitable for adding turbulent atmospheric effects to theoretical low‐boom waveforms. Filter functions have been created based on a measured input‐output relationship. The input is a relatively clean sonic boom waveform measured at altitude by a glider, and the outputs are turbulized’ waveforms measured on the ground. One input waveform and multiple output waveforms are used to represent multiple realizations of the atmosphere. Work presented in 2005 [Locey and Sparrow, Innovations in Nonlinear Acoustics, 17th International Symposium on Nonlinear Acoustics (American Institute of Physics, Melville, NY, 2006)] yielded an initial set of filter functions using one particular algorithm and data collected during the Shaped Sonic Boom Experiment (SSBE) in January of 2004. In this talk new results will be presented based on high‐fidelity measurements made at NASA Dryden Flight Research Center in June of 2006 [T. Gabrielson et al., Proc. Internoise (2006)]. Time permitting, additional methods for obtaining filter functions will be discussed, including the use of existing sonic boom propagation codes modified to include atmospheric turbulence. [Work supported by the FAA/NASA/Transport‐Canada PARTNER Center of Excellence for Aircraft Noise and Aviation Emissions Mitigation.]