Sound transmission in the spermaceti complex of a recently expired sperm whale calf

Abstract

Sound pulses were projected into the forehead of a neonate, female sperm whale that died following a stranding and attempts to revive it. Two hydrophones, held against the skin, recorded the sound pulses and their reflections. A consistent reflection was found about 0.8 ms after sound projection. This time corresponded to the expected two-way travel time back and forth within the spermaceti organ. Reflections were also detected at the frontal surface of the junk from sounds projected into the distal sac area. These signals must have traversed rearward along the axis of the spermaceti organ to the frontal sac where they were likely reflected and directed forward to the front of the junk, demonstrating an acoustic continuum between the spermaceti organ and the junk. These results support the basic Norris and Harvey (1972) theory of sound generation in sperm whales and later amendments to that theory (Mohl and Amundin (1991), Mohl (2001)).