  Large-scale turbulent structures in the form of coherent wavepackets play a
significant role in the generation of prominent shallow angle noise radiation
of jets. Economical prediction tools often model these wavepackets in the
frequency-domain using stability modes of the mean flow. The use of simplifying
choices, such as parabolized equations and azimuthal decomposition, provide
efficient methods but can impose constraints on rate of streamwise variation of
the mean state or geometric complexity. The current investigation develops a
time-domain linearized Navier-Stokes-based approach predicated on the mean
basic state for two goals: i) to obtain the radiated shallow-angle noise field,
including that from imperfectly expanded jets containing shock trains, and ii)
to estimate noise control trends with actuator frequency. A previously
developed implicit linearization technique repurposing native non-linear
Navier-Stokes code capabilities avoids any additional constraints on nozzle
geometry, while its time-domain nature facilitates control analysis through
transient pulse response. Two other integral components of the method are the
sifting of linearized perturbations to isolate the acoustic component with
Doak's Momentum Potential Theory, and subsequently Dynamic Mode Decomposition
to analyze the response in different spectral ranges. Comparisons with
well-validated LES databases show accurate model predictions for
super-radiative shallow angle noise, including for hot jets from military-style
nozzles. For a specific jet with extensive published experimental data using
plasma actuators, it is shown that the method correctly predicts noise
amplification at lower frequencies and reduction at higher values, at the
observed crossover location. Considerations on the costs associated with the
approach, which exploits linearity to extract multiple frequencies with each
simulation, are outlined.
