SOUND PRODUCTION BY MARINE ANIMALS 



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Fig. 9. Sound spectrogram of call of Euhalaena glacialis (right whale). 



they exhibit a preponderance of energy in the lower middle part of the spectrum, 

 often between about 4 and 12 kc/s, but this appearance is largely due to the 

 uneven response of the recording system (hydrophone — amplifier — recorder), 

 and is not necessarily true of the sound made by the whale. Fig. 10 shows such 

 a spectrogram of Physeter (sperm whale) clicks. This whale uses clicks ap- 

 parently exclusively and with greater intensity than other odontocetes ; 

 although we have listened to many sperm whales during the last three years, 

 we have never heard a squeal, only these powerful clicks. Fig. 4 includes clicks 

 of Delphinus delphis, the familiar oceanic porpoise (or "common dolphin"). 



The odontocete squeals are quite different in character, being sharply 

 limited in frequency and considerably extended in time. Fig. 4 is a spectrogram 

 of a squeal of Delphinus delphis. This sound is sufficiently intense to be heard 

 in favorable circumstances by the unaided human ear in air (McBride, 1940; 

 Kullenberg, 1947; Fraser, 1947), and is what led arctic seafarers to call Del- 

 phinapterus (white whale) the "sea canary". 



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Fig. 10. Sound spectrogram of clicks of Physeter catodon (sperm whale). 



