Audiogram of the California sea lion in air (Zalophus californianus)
Data from:
Schusterman, R.J. (1974) Auditory sensitivity ofthe California sea lion to airborne sound. Journal of the Acoustical Society of America, 56, 1248-1251. one animal (values below 24 kHz notlisted as they were affected by noise)
Schusterman, R.J. (1981) Behavioral capabilities of seals and sea lions: A review of their hearing, visual, learning and diving skills.Psychological Record, 31, 125-143. one animal
Kastak, D., and Schusterman, R.J. (1998)Low-frequency amphibious hearing in pinnipeds: Methods, measurements, noise,and ecology. Journal of the Acoustical Society of America, 103,2216-2228. one animal, headphones
Absolute thresholds (in dB re 20 µN/m2) for three California sea lions (designated A through C as indicated above)
|
Frequency (in kHz) |
Individual Thresholds (in dB) |
Average |
||
|
Schusterman 1974 |
Schusterman 1981 |
Kastak & Schusterman |
||
|
.100 |
— |
— |
77.5 |
78 |
|
.200 |
— |
— |
57.5 |
58 |
|
.400 |
— |
— |
59.2 |
59 |
|
.800 |
— |
— |
63.1 |
63 |
|
1 |
— |
41 |
— |
41 |
|
1.6 |
— |
— |
56.9 |
57 |
|
2 |
— |
19 |
— |
19 |
|
3.2 |
— |
— |
48.1 |
48 |
|
4 |
— |
26 |
— |
26 |
|
6.4 |
— |
— |
31.4 |
31 |
|
8 |
— |
16 |
— |
16 |
|
16 |
— |
28 |
— |
28 |
|
24 |
37 |
37 |
— |
37 |
|
28 |
41 |
— |
— |
41 |
|
32 |
52 |
61 |
— |
57 |
Lowest and highest frequencies audible at sound pressure levels (SPL) ranging from 30 to 70 dB SPL
|
SPL (in dB) |
Lowest audible frequency (in kHz) |
Highest audible frequency (in kHz) |
|
70 |
.130 |
— |
|
60 |
.180 |
33 |
|
50 |
.420 |
30 |
|
40 |
1 |
28 |
|
30 |
1.4 |
17.5 |
Additional Parameters:
Body weight = 160 kg
Functional interaural distance= 392 µs
(Time required for sound to travel around the head from one auditory meatus to the other.)
Comments: Threshold values taken from Schusterman, 1974,1981, and Kastak and Schusterman 1998.
See Kastak and Schusterman, 1998 for a good discussion of the difficulties associated with measuring low-frequency hearing in amphibious species