Phase evaluation in hypothetical receivers simulating ranging in bats.

Echo delay discrimination by the bat Eptesicus fuscus had been investigated in an experiment with simulated targets jittering in range (Simmons 1979). The dip in the resulting psychometric curve was used by Simmons to suggest the neuronal implementation of a coherent cross-correlation receiver in the auditory system of bats. By computer simulation it is shown here that the dip may be even more pronounced and less susceptible to noise with alternative receiver configurations which not necessarily evaluate signal phase information coherently, e.g., a bank of neuronal filters with envelope-processing. New behavioral experiments are suggested to critically test such model hypotheses.