Preliminary similarity spectra analysis of noise from a high-performance trainer aircraft

Because the noise source mechanisms and radiation properties associated with high-thrust, tactical jet engines are not fully understood, analysis of full-scale measurements can shed significant insight on such characteristics. One method for examining spectral data is to compare them to empirical models for jet noise spectra. This paper compares measured near-field spectra from a T-7A-installed GE F404-103 engine with analytical similarity spectra for fine-scale mixing noise, large-scale mixing noise, and broadband shock-associated noise. This initial similarity spectra analysis enables the determination of spatial trends in overall level and peak frequency and the relative importance of each type of noise radiation as a function of location. This approach can be used to gain insights on spatial and frequency trends of noise source mechanisms for different engine conditions and for rapid comparisons to other aircraft and jets of other scales and conditions.