Acoustic reflectivity of a dolphin

Backscatter measurements were made on a stationary Atlantic bottlenosed dolphin under controlled conditions. Three sets of measurements were made: (1) broadside aspect target strength as a function of frequency from 23 to 80 kHz; (2) relative target strength as a function of the polar angle about the animal using a short click signal having:apeak frequency of 67 kHz; and (3) relative reflective strength of different portions of the animal's body. The mean target strength at the broadside aspect decreased from -11 to -24 dB as the frequency increased from the frequency increased from 45 kKz, the target strength ruse to a local maximum of - 18 dB at 66 kHz and then decreased to -23dB at 79 kHz. Maximum target strength was measured at the broadside aspect and exceeded the minimum (tail aspect) target strength by 21 dB. The target strength at the head aspect was 5 dB below that of the broadside aspect. Most acoustic energy was reflected from the area between the dorsal and pectoral fins. corresponding to the location of the dolphin's lungs.