A hearing evaluation and hearing aid fitting system provides a fully immersive three-dimensional acoustic environment to evaluate unaided, simulated aided, and aided hearing function of an individual. Digital filtering of one or more signal sources representing speech and other audiologically significant stimuli according to selected models and digitally controlled signal processing parameters, including audio sources, spatializing coordinates, acoustic boundaries, signals representing one or more simulated hearing aids, and individualized body/external ear transfer functions synthesizes a simulated acoustic condition for presentation to a hearing-impaired person for objective and subjective hearing evaluation via an intra-canal prosthesis that is positioned in the ear canal, and that incorporates a microphone probe to measure in-the-ear-canal responses at a common reference point near the tympanic membrane during unaided, simulated aided, and aided hearing evaluation, thus providing measurements that are directly correlated across all phases of hearing assessment during the fitting process of a hearing aid. A virtual electroacoustic audiometer computes the electroacoustic parameters of a hearing aid based on the results of unaided audiometric evaluation and reference measurements that include the individual's acoustic responses near the tympanic membrane to acoustic stimuli in three-dimensional acoustic space. The system then synthesizes acoustic signals reflecting the combined selection of audio signal model, spatialization model, acoustic boundaries model, as well as computed hearing aid model in the case of simulated aided condition.