The mammalian auditory system is a highly evolved acoustic signal-processing system that performs well even in highly reverberant and cluttered acoustic environments. In echolocating species, the auditory system is even more highly evolved and is generally more important than vision for navigation and foraging. Since invasive physiological experiments using echolocating species is challenging at best and is illegal for protected species, other methods must be sought if we are to understand how biosonar systems function. Biophysically based computer models provide a method by which we can extrapolate from physiological experiments performed on species that can be used for invasive experiments to those species that cannot be used. Results will be presented for simulations of physiological responses in the auditory nerve and brainstem to biosonar signals for several species. The simulations were done using the EARLAB (http://earlab.bu.edu) desktop simulation environment. Model parameters for species of interest were estimated from behavioral audiograms and from other available data. The models can be used to predict how different types of biosonar signals are represented in neural firing patterns and how the neural representation degrades in the presence of anthropogenic noise. [Work supported by ONR and NSF through the NOPP program.]