Upcoming Colloquia

Wednesday, January 24

4:00 PM, Provo

Tracianne Neilsen

Brigham Young University

Self-similarity in supersonic jet noise

Self-similarity appears in many physical systems, from phase transitions to plants to musical instruments. Self-similar behavior appears the same on different scales, and is a component of critical phenomena.  The turbulent flow and resulting noise from high-speed air jets exhibit self-similarity when scaled by the jet nozzle diameter and velocity. Examples of this behavior are found in laboratory-scale air jets, military aircraft engines, rocket motors, and explosive volcanoes. In particular, the spatial variation in the noise spectrum is self-similar and can be fit with empirically determined similarity spectra. This self-similarity can be used to develop a broadband equivalent source model that adequately predicts the sound radiation over a large spatial aperture, with only a few exceptions.  The resulting level-based equivalent source models can lead to improved sound level estimates for community noise exposure and aircraft maintainer’s noise dosage limitations.


Dr. Tracianne B. Neilsen, currently a part-time professor at Brigham Young University, earned her doctorate from the University of Texas at Austin, and completed a postdoctoral appointment at the associated Applied Research Laboratories.  Her research areas include management and analysis of large acoustic data sets, numerical modeling of acoustic fields, and application of multi-dimensional inversion techniques to measured data for source characterization and sound field imaging.  Her initial research activities centered on the estimation of source locations and seabed parameters from shallow-water acoustic data via adaptive inversions.  Since coming to BYU, she has shifted from underwater sound to studying high-amplitude aero-acoustics, including military aircraft noise. Her current research on the analysis of military jet aircraft noise includes examining near-field propagation effects, equivalent jet noise sources, including wave packets, and inverse methods such as near-field acoustical holography and beamforming. She has recently constructed a broadband, level-based equivalent source model for jet noise that shows promise for noise exposure estimation and environmental noise modeling.

We welcome anyone who wish to attend, and typically serve refreshments ten minutes before the colloquium begins. Speakers generally keep their presentation accessible to undergraduate physics students.