Morell, M., Degollada, E., van der Schaar, M., Delory, E., Alonso, J.M., López, A., André, M. CT Scan 3D reconstruction of the ear related with the Acoustic sensitivity in harbour porpoise (Phocoena phocoena) 20th Conference of the European Cetacean Society, Gdynia, Poland, Apr 2006 Résumé: Understanding the acoustic capacity of harbour porpoises to detect fishing nets is a key conservation issue to prevent their entanglement. Although the maximum auditory sensitivity of the species corresponds with the peak frequency of echolocation pulses produced by harbour porpoises (~120-130kHz), results from standard psycho-acoustic techniques suggest that this species is also sensitive to lower frequencies (below 20kHz). Here, we investigate the acoustic response through 3D reconstruction and measurements of the tympano-periotic complex (including cochlea lengths and volumes) and relate them with the reported auditory sensitivity. We further compare these measurements with the results (3D reconstructions and audiograms) from other echolocating species. A constant periotic-tympanic volume ratio is showed, that may indicate the functionality and the possible role of the middle ear during target acoustic detection Projet: Noise pollution effects on cetaceans