The Fechner-Weber law states that for a sensation’s intensity to increase in an arithmetic progression, the stimulus must increase in a geometric progression. This relation describes sensory perceptions and physical stimuli for hearing. Human hearing can detect noise so quiet that the eardrum moves less than an atom’s width, and noise 10 trillion times more …
Category Archives: Acoustics
Linear to Nonlinear Relations in Wave Science (Acoustics)
In the realm of acoustics or wave science, the transition from linear to nonlinear physics marks a significant evolution in the understanding of tones and their generation. The foundation of this understanding dates back to Pythagoras, who established a linear relationship between the length of a plucked string and the resultant musical tone. This principle …
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Analytical Closed-Form Solution of the Navier-Stokes Equations for the Aerodynamic Near-field and Sonic Boom from Axisymmetric Bodies
I completed my Acoustical Society work and returned to the United States. Abstract: An analytical closed-form solution is presented for the aerodynamic near-field and ground signature from an axisymmetric body with a low thickness ratio. The Navier-Stokes equations are formulated as a boundary value problem that incorporates the incoming ambient flow-field and the aerodynamic properties …
Aeroacoustic and Aerodynamic Interaction Effects Between eVTOL Rotors
My student presented his MS thesis on the aerodynamics and aeroacoustics of rotors. Abstract: Electric vertical take-off and landing (eVTOL) aircraft are characterized by their unconventional wing and electric rotor configurations, which involve both side-by-side and tandem rotor configurations. These configurations create unique aerodynamic and aeroacoustic flow-fields. We numerically investigate the interaction effects between rotor …
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A simplified semi-empirical model for long-range low-frequency noise propagation in the turbulent atmosphere
My student, Dr. Tianshu Zhang, and myself recently published a modified long range acoustic propagation model that handles turbulence in the atmosphere. The abstract is We present a semi-empirical long-range low-frequency acoustic propagation model, which accounts for atmospheric turbulence. Ostashev and Wilson’s scattering model is combined with a ray-theory based refraction model to account for …
AIAA SciTech 2023
This year, some of my students and collaborators are going to the AIAA SciTech conference in the DC area in the National Harbor, MD. We are presenting two particular papers. The first involves hypersonic flow-fields and the second involves acoustics and aerodynamic experiments. The citations, papers, and presentations are:
Acoustical Society of America – December 2022
This year my research group had a good showing at the Acoustical Society of America, Dec. 2022. I was happy to give a 20 minute talk myself on jet and rocket coherence and loading. My student, Dr. Alex Carr, who is now a Research Aerospace Engineering at NASA reported on his sonic boom predictions. My …
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Mach Experiment
Thomas D. Norum
My good friend Thomas D. Norum recently passed away. He worked as a researcher at NASA Langley over most of his career. I knew him starting in 2009 through 2016 while I was working there. He worked as an experimentalist in the jet noise lab of NASA Langley. As an experimentalist, he worked to understand …
Numerical prediction of loudness metrics for N-waves and shaped sonic booms in kinematic turbulence
Abstract, “The effects of a kinematic field of velocity fluctuations on the loudness metrics of two waveforms are examined with a three-dimensional one-way propagation solver. The waveforms consist of an N-wave and a simulated low-boom from NASA’s X-59 QueSST aircraft. The kinematic turbulence is generated using a von Karman composite spectrum, which is dependent on …