This work presents a biologically motivated neuronal model for detecting the elevation of unfamiliar natural sound sources using monoaural cues, based on head-related-transfer functions. This model can determine the elevation of an unfamiliar sound source to within less than 43 with no error using very small number of training samples. In addition, we suggest that the approximate logarithmic response of the cells in the cochlea is bene"cial for localizing unfamiliar sound sources. 2000 Elsevier Science B.V. All rights reserved.