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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)

Ìý Frequency (in kHz)	Individual Thresholds (in dB)			Ìý 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