Responses were noted throughout those frequencies with maximum sensitivities 

 found at approximately 45 dB at 8 and 32 kHz. High sensitivity was noted from 

 4-64 kHz. Below 4 kHz the thresholds decreased to 85 dB at 1 kHz (15 

 dB/octave). Above 40 kHz thresholds decreased to 70 dB at 150 kHz (15 

 dB/octave) and to at least 150 dB at 150 kHz (700 dB/octave). 



Sukhoruchenko (1973) used a respondent (Francis, 1975) or Pavlovian 

 conditioning training technique. This was the only behavioral measurement 

 technique not to use operant conditioning. Twenty Phocoena phocoena were 

 preconditioned with a mild shock to the presentation of a tone. An 

 electromyogram (EMG) was produced from skin-mounted electrodes monitoring the 

 muscle twitch in the skin resulting from the shock. The shock was faded out 

 of the experiment after the muscular action was conditioned to the tone. By 

 monitoring the EMG to the onset of tones with varying frequency and 

 intensities, an audiogram was obtained from 3 - 190 kHz. Maximum sensitivity 

 was at 60 dB at 64 kHz. High sensitivity was from 10 - 90 kHz. The results 

 reported are averages of the twenty test subjects. 



The auditory studies of Delphinus delphis report only frequency 

 thresholds (Bel'kovich and Solntseva, 1970). Correct responses to the signal 

 were indicated by the animal swimming towards a lever and vocalizing. Four 

 series of test frequencies were run. The first series contained frequencies 

 from 660 Hz - 206.6 kHz. Responses up to 119.2 kHz were noted. Frequencies 

 from 120 - 206 kHz elicited a negative response (tail slaps and fast 

 swimming). The authors reported this was due to the animal's dislike of the 

 signal. They felt this warranted inclusion in the threshold report. The 

 third series of tests were run from 16 Hz - 3.73 kHz and elicited responses in 

 eyery case. In the final series, frequencies from 200 - 400 kHz were used. 

 Above 290 kHz responses were inconsistent. The authors reported responses to 

 frequencies as high as 320 kHz. They concluded that the auditory perception 

 of Delphinus delphis ranges from 18 Hz - 280 kHz. These tests were repeated 

 on another animal with the same results. 



In 1970 auditory threshold research on Orcinus orca was conducted by 

 Hall and Johnson (1972) at Sea World of San Diego. The young male test 

 subject responded from 500 Hz, the lowest frequency presented, to 31 kHz. 



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