The cetaceans appear to have a 20-30 dB superiority over the pinnipeds 

 in their respective regions of greatest sensitivity, and except for the killer 

 whale, their audition extends one to two octaves beyond that of the pinnipeds. 



Sound Production of Marine Mammals 



Although little information is currently available on the sounds 

 perceived by large whales, it is generally assumed that most animals can hear 

 sounds similar to those that they produce. A major portion of the regions of 

 peak sensitivity fits well the animals' own signal characteristics (Diercks, 

 Trochta and Evans, 1973). These similarities correlate with those noted for 

 some species of fish and other animals for which similar data are available. 

 Marine mammals have a broad repertoire of sounds, the echolocation pulses of 

 the dolphin being the best documented. The high-frequency character of the 

 echolocation clicks is reflected in the high-frequency sensitivity of these 

 animals. 



Caution should be exercised in limiting the received bandwidth of sounds 

 based solely on those that a large whale produces. Tables 4 and 5 summarize 

 source level data for cetaceans with corresponding peak frequency bands or 

 sound characters. These values are typically based on peak energy levels in 

 relatively narrow bandwidths. 



Broadband (1 kHz - 40 kHz) recordings for four species of toothed whales 

 were presented by Fish and Turl (1976). These included the northern right 

 whale dolphin, Lissodelphis boreal is ; the Pacific bottlenose dolphin, Tursiops 

 truncatus; the Pacific pilot whale, Globicephala macrorhynchus ; and the common 

 dolphin, Delphinus delphis . The data for these species showed that source 

 levels were not confined to narrow bandwidths, as presented in Tables 4 and 5, 

 but can cover a broad frequency range. 



Thompson, Winn and Perkins (1979) classified mysticete sounds into four 

 groups. Group I includes low frequency moans from 0.4 to 36 seconds long, 

 with the fundamental frequencies from 12 to 500 Hz. Moans may contain strong 

 harmonic structures or pure tones. All but the sei whale, Balaenoptera 

 borealis , and the minke whale, Balaenoptera acutorostrata , are known to make 

 these sounds. Group II includes grunt-like thumps and knocks of short 



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