The source level data from offshore drilling activities specify the amount of sound 

 energy radiated by a projector measured 1 m from the source. 



The anatomy and function of the auditory and audio-neural structure of several 

 species of small cetaceans have been reviewed (ref 1 1-16). Electrophysiological recordings 

 and cochlear microphonic measurements (ref 13) support the hypothesis that sound is 

 received via bone conduction through the fat layer of the lower jaw (ref 16) for small toothed 

 whales. 



The anatomical structure of the mysticete (large whales) auditory structure has been 

 reviewed (ref 17-19). Mysticete cochlea are structurally sensitive to low frequency sounds; 

 however, these animals may be capable of hearing higher frequencies (ref 20). Anecdotes 

 suggest that large whales respond to ship noise, sonar pings and low flying aircraft (ref 21). 



The pinniped external ear accommodates in-air and underwater hearing. Underwater, 

 the pinniped head may conduct sound directly to the organ of Corti, whereas aerial sound 

 transmission apparently is typically mammalian (ref 22). 



' ' Morgane, JP and NS Jacobs, Comparative Anatomy of the Cetacean Nervous System, In; Functional 

 Anatomy of Marine Mammals, Vol 1 , RJ Harrison, ed, p 117-244, Academic Press, New York, NY, 1972. 



'•^ Bullock, TH, AD Grinnel. E Ikezono, K Kameda, Y Katsuki, M Nomoto, N Sato and K Yanagisawa. 

 Electrophysiological Studies of the Central Auditory Mechanism in Cetaceans, Z VergI Physiol 59, p 1 17- 

 156, 1968. 



^^ McCormick, JG, EG Wever, J Palin and SH Ridgway, Sound Conduction in the Dolphin Ear, J Acous Soc 

 Amer, 48(6), p 1418-1428, 1970. 



''^ Wever, EG, JG Mc Cormick, J Palin and SH Ridgway, The Cochlea of the Dolphin, Tursiops tnincatus: 

 General Morphology, Proc Nat Acad Sci, 68(10), p 2381-2385, 1971. 



^^ Eraser, EC and PE Purves, Hearing in Cetaceans, Bull of Brit Mus, 7, p 1-140, 1960. 



"Norris, KS, The Echolocation of Marine Mammals, In: The Biology of Marine Mammals, HT Harrison, ed, 

 p 391-423, Academic Press. New York, 1969. 



Reysenback de Haan, FW, Hearing in Whales, Acta Otolaryngal, 134, p l-1 14, 1957. 



'^ Dudok van Heel, WH, Sound and Cetacea, Neth J Sea Res, 1(4), p 407-507. 



Purves, PE, Anatomy and Physiology of the Outer and Middle Ear in Cetacea, In: Whales, Dolphin and 

 Porpoise, KS Norris, ed, Univ of Calif Press, p 320-380, 1966. 



'• Fleischer. G, Hearing in Extinct Cetaceans as Determined by Cochlear Structure, J Paleontol, 50(1), 



p 133-152, 1976. 



-^ Norris, KS and RR Reeves, eds. Report on a Workshop on Problems Related to Humpback Whales 

 (Megaptera novaeangliae ) in Hawaii, US Dept Comm, NTIS PB-280-794, p 90, 1978. 



"" Reppening, CA, Underwater Hearing in Seals, In: Functional Anatomy of Marine Mammals, RJ Harrison, 

 ed, p 307-331, Academic Press, New York. 1972. 



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