Abstract

Noise fields generated by high-performance military jets are known to contain acoustic structures that differ from their simulated and lab-scale counterparts. These differences may limit current noise control efforts, which are designed and tested at scale before being considered for full-scale aircraft. One such noise structure is the presence of spatiospectral lobes, which appear as multiple spectral peaks at single microphone locations and multiple radiation lobes in field reconstructions. This dissertation uses data collected from the T-7A jet noise measurement to characterize the spatial behavior of the spatiospectral lobes as well as their first time-domain description. A multiple wavepacket decomposition of the T-7A equivalent source model is used to reduce the model complexity and identify underlying partial sources connected to the lobes. Beyond the spatiospectral lobe analysis, this dissertation also addresses theoretical gaps in acoustic radiation surrounding partially coherent sources, such as those produced by a military jet. The first investigates how coherence impacts a jet's radiated sound power and under what conditions partial coherence is important. The second presents an analytic framework for determining the diffracted pressure field from an extended, partially coherent source in the presence of a barrier with arbitrary acoustic impedance. The contributions of this dissertation are relevant for future full-scale military jet noise reduction efforts in terms of accurate noise modeling and field radiation beyond a freefield environment.

Degree

PhD

College and Department

Computational, Mathematical, and Physical Sciences; Physics and Astronomy

Rights

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