Underwater hearing sensitivity of harbor seals (Phoca vitulina) for narrow noise bands between 0.2 and 80 kHz.
The underwater hearing sensitivities of two 1.5-year-old female harbor seals were quantified in a quiet pool built specifically for acoustic research, by using a behavioral psychoacoustic technique. The animals were trained to respond when they detected an acoustic signal and not to respond when they did not ("go/no-go" response). Fourteen narrowband noise signals (1/3-octave bands but with some energy in adjacent bands), at 1/3-octave center frequencies of 0.2-80 kHz, and of 900 ms duration, were tested. Thresholds at each frequency were measured using the up-down staircase method and defined as the stimulus level resulting in a 50% detection rate. Between 0.5 and 40 kHz, the thresholds corresponded to a 1/3-octave band noise level of approximately 60 dB re 1 microPa (SD+/-3.0 dB). At lower frequencies, the thresholds increased to 66 dB re 1 microPa and at 80 kHz the thresholds rose to 114 dB re 1 microPa. The 1/3-octave noise band thresholds of the two seals did not differ from each other, or from the narrowband frequency-modulated tone thresholds at the same frequencies obtained a few months before for the same animals. These hearing threshold values can be used to calculate detection ranges of underwater calls and anthropogenic noises by harbor seals.
Kastelein
Ronald A
RA
Sea Mammal Research Company (SEAMARCO), Harderwijk, The Netherlands. researchteam@zonnet.nl
Wensveen
Paul
P
Hoek
Lean
L
Terhune
John M
JM
D000161:Acoustic Stimulation; D000818:Animals; D001309:Auditory Threshold; D005260:Female; D006309:Hearing; D009483:Neuropsychological Tests; D046049:Phoca; D011571:Psychoacoustics; D014867:Water
D014867:Water