Transcript Sounds in the sea - Ocean Mixing Group

Underwater hearing
(of vertebrates)
Human ear
The inner ear
Fish ears
Odontocete receiving system
“Acoustic fat” found
ONLY here & melon
CT scan from
Darlene Ketten
How do we test hearing?
• Behavioral methods
– Animal trained
– Responds
• Go/no-go
• 2 alternative choice
• Auditory brainstem response
– No training required
– Record firing of auditory cortex
• Usually test pure tones
• Occasionally test pulses
– Thresholds much lower for pulsed sounds than pure
tones
Up-down staircase procedure
50% ‘catch trials’ (no signal present)
Envelope
following
response
Supin et al.
Envelope following response ABR
ABR threshold calculation
Magnitude
ABR
Behavioral vs. ABR
Yuen et al. 2005
Behavioral vs. ABR
• Behavioral
– Requires months to train, months to test
– Usually only 1 subject
• ABR
– Requires no training, rapid testing
• Can be used to test for transient effects
– Can be done on more species e.g. stranded animals,
catch and release animals
• Both require placement of a threshold that varies
with conditions
Fish hearing
Tuna
Damselfish
Salmon
Carp (goldfish)
Cod
Popper et al.
3 types of fish ears
• General fish
– No hearing specialization
– 100-1,000 Hz
– Best hearing 100-400 Hz
• Specialized hearing
– Goldfish, catfish, etc.
– 100-3,000 Hz
– Best hearing 300-1,000 Hz
• High frequency adaptations
– Clupeids (herring, shad, menhaden, sardine, anchovy)
– Swimbladder morphology facilitates broad frequency hearing
range
– 1-200,000+ Hz
Cetacean hearing
Human
From: Au, 1993
Pinniped external ears
Elephant seal
Harbor seal
Sea lion
Kastak et al. 1999
Pinniped in-air hearing
Kastak et al. 1999
Pinniped underwater hearing
Kastak et al. 1999
Fur seal
Harbor seal
In air vs.
underwater –
pressure or
intensity?
Pressure – assumes hearing mechanism
Intensity – corrects for acoustic
properties of media. Energy flow measure
Does not require knowledge of stimulus
mechanism
Elephant seal
Phocids (true seals) generally hear
equally well in air and underwater –
amphibious
Elephant seal – a deep diver hears
better underwater (bone conduction in
air)
Fur seals hear better in air – primarily
terrestrial socialization and mating
Hearing curves combined
Sea lion
Bottlenose dolphin
Cod
Catfish
Harbor porpoise
Project “Deep EAR”
• Human hearing attenuates with increasing
pressure (chamber experiments)
• Beluga whales (a dolphin species)
experience large pressure increases with
diving
• Effects on whistling and hearing in freeswimming animals
Ridgway, S. H. et al. J Exp Biol 2001;204:3829-3841
Up to 40 tones were presented to the whale during a dive
Ridgway, S. H. et al. J Exp Biol 2001;204:3829-3841
Depth effects – Beluga whales
“Deep EAR” results
• Increasing pressure
(up to 300 m dives)
• Did not affect hearing
• Changed whistle
spectra and intensity
• One whale only
clicked at 300 m
depth
Diving and elephant seal hearing
Kastak et al. 2001
Temporary threshold shifts
• Aural fatigue
• Hearing threshold increased
• Recovery follows with varying time course
(minutes – weeks)
• Experiments in chinchillas and humans
have shown the relationship between TTS
and PTS (permanent threshold shifts)
• Good predictor of auditory damage
TTS
Finneran et al 2005
Temporary threshold shifts
• Longer exposures to quieter sounds have
the same effect as shorter exposures to
louder sounds
• Exposure intensity usually relative to
hearing threshold except for impulsive
sounds
• The total exposure energy of the sound to
which an animal is exposed important
Signal effects on hearing
• Received intensity (source level + range +
environmental conditions)
• Frequency
• Duration
• Timing (spacing between sounds)