A computional model is developed for prediction of noise emission from na existing or new turbofan engine. This model allows the simulation of noise generation from high bypass ratio turbofan engines, appropriate for use with computational programs for gas turbine performance developed at ITA. Analytical and empirical methods are used for spectrum shape, spectrum level, overall noise and free-field directivity noise. The most significant noise sources in turbofan engines are modeled: fan, compressor, combustion chamber, turbine, jet (separate streams or mixed jet), with corrections for forward speed, atmospheric attenuation, ground reflection, and nacelle acoustic treatment (perforate liners). The procedures for component noise prediction are combined to yield total turbofan engine noise emission, as a funtion of engine operation condition and of observer (distance and directivity angle).