Aircraft flyover noise prediction

A review is conducted of the prediction techniques for CTOL aircraft noise sources which are presently implemented in the NASA Aircraft Noise Prediction Program (ANOPP). The sources considered include jet noise, fan noise, combination noise, and airframe noise. Questions related to propagation prediction methods, source shielding, atmospheric attenuation, and ground attenuation are also described. It is pointed out that ANOPP is designed to make predictions of varying degrees of complexity, or amounts of detail, depending on the needs of the user. These different degrees of complexity are called levels of prediction. The prediction methods being used imply a similarity law for aircraft noise. Propulsion noise is proportional to mass flow for a selected engine cycle and, since thrust is also proportional to mass flow, aircraft with a fixed thrust-to-weight ratio will have their propulsion noise proportional to weight.