< 



0. 



a. 



• HARBOR SEAL 



o HARP SEAL 



A RINGED SEAL 



V CALIFORNIA SEA LION 



1000 



FREQUENCY (kHz) 



Figure 9. Behavioral underwater audiograms (smoothed curves) for the California 

 sea lion, the harp seal, the ringed seal and the harbor seal. 



SOUND PRODUCTION AND HEARING OF LARGE WHALES 



The hearing sensitivities of large whales have not been measured. It is assumed that 

 most animals can hear the sounds they produce; however, we cannot determine the limit of 

 the receiving bandwidth of large whales without direct measurements. Source level and fre- 

 quency data for cetaceans are summarized in table 2. These reported values are peak energy 

 levels in relatively narrow bands. Broadband source level measurements are presented in 

 reference 39 for four species of small toothed whales (the common dolphin, the northern 

 right whale dolphin, the Pacific pilot whale and the Pacific bottlenosed dolphin). The values 

 shown in table 2 suggest that sounds produced by large whales are restricted in frequency; 

 however, these values probably reflect the manner in which source level data normally are 

 presented as narrow band measurements. 



Reference 58 classifies mysticete sounds into four categories. Group I includes low 

 frequency moans with fundamental frequencies from 12 to 500 Hz. The moans generally 

 contain harmonically structured pure tones. Except for the sei and minke whales, all 

 mysticetes make these sounds. Group II sounds include grunt-like thumps and knocks of 

 short duration. The humpback, right, bowhead, grey, fin and minke whales produce these 

 sounds. Major energy in Group II sounds is between 40 and 200 Hz. Group III sounds con- 

 tain chirps, cries and whistles above 1.0 kHz. Chirps generally are pulses of short, discrete. 



r5Q 



Naval Undersea Center TP 547, Acoustic Source Levels of Four Species of Small Whales, by JF Fish and 

 CWTurl, p 14, 1976. 



^^ Thompson, TJ, HE Winn and PJ Perkins, Mysticete Sounds. In: Behavior of Marine Mammals. Vol 3, 

 Cetaceans, HE Winn and BL OUa, eds, p 403-431, Plenum Press, 1979. 



H-18 



