CUMMINGS ET AL.: SOUND FROM BRYDE AND FINBACK WHALES 



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TIME SCALE I 1 



1 SECOND 



Figure 7— Spectrograms of whale blow series recorded in air. Running time in seconds relative to the first blow is indicated on the abscissa. 

 Whales II and III (second series) can be distinguished throughout the first 105 min by the unique physical characteristics of their alter- 

 nating blows. Just before a long dive, the whales produced a low-frequency whistlelike sound at inhalation Oast spectrogram, first row; 

 last spectrogram, last row) which was not apparent during earlier blows of a series. In the second series, two low-level blow sounds at 

 110 and 132 min are not shown. The effective analyzing filter bandwidth was 20 Hz. 



DISCUSSION 



The moans recorded on this cruise from visually 

 unidentified or unseen whales were very similar to 

 those found to be from finbacks, except for Contact 

 3 involving Bryde whale sounds. Thus we believe the 

 former also were from finback whales. 



Some of the moans recorded in this study only 

 slightly resembled short "20-Hz signals" described 

 by several investigators (Walker 1963; Patterson and 

 Hamilton 1964; Schevill et al. 1964; Weston and 

 Black 1965; Cummings and Thompson 1966 [fn. 4]; 

 Northrop et al. 1968; Watkins 1981). However, none 

 of the presently described signals could be categ- 

 orized as short "20-Hz signals" noted in other 



studies, because of differences in frequency (Hz) of 

 major sound energy, signal repetition, and inter- 

 vals between repetitions. Typical short "20-Hz 

 signals" are narrowband pulses with principal sound 

 energy near 20 Hz. They are repeated at remark- 

 ably constant intervals. Only about 3% of the 

 sounds reported here had components as low as 20 

 Hz. 



The miscellaneous moans that were recorded from 

 finbacks mainly resemble the category that Watkins 

 (1981) called "higher frequency sounds". However, 

 most of his recordings of these sounds were down- 

 ward-sweeping pulses, eg., 75-40 Hz, with emphasis 

 around 40 Hz. We did not record sounds similar to 

 Watkins' low-frequency rumble or ragged pulse 



367 



