1. Test audio/video

2. Acoustics and Biology Acoustics
loudness (intensity) and pitch (frequency)
How to read a spectrogram
Use of sound by marine animals
Predation and defense
Echolocation
Communication and social interaction
Signal-to-noise ratio
Man-made sounds and their effects on animals

3. Anatomy of a sound wave a T T = period of wave a = amplitude of wave
f = frequency = 1/T
λ = wavelength (= cT = c/f, where c is sound speed)

4. Amplitude determines sound level pressure, this determines loudness
a = amplitude a a
These waves have the same frequency and wavelength but different amplitude

5. Loudness
(Amplitude, sound level)
SL(dB)=20 log10(P/Pref)
SL(dB)=10 log10(I/Iref)
Chart shows loudness in dB of some familiar sounds
Sound levels in air and water have different reference levels, so
0 dB (air) ≈ 26 dB (water)

6. Frequency determines “pitch”
Frequency f = 1/T, wavelength λ= c/f T T
These waves have the same amplitude but different period, frequency, and wavelength

7. Pitch (frequency) Larger instruments produce lower frequencies
Instrument Range measured in dB
Bass drum
Cymbal
Organ
Piano
Trumpet
Violin
Larger instruments produce lower frequencies
Instrument dB
Bass drum
Piano
Trumpet 55-95
Violin
Voice

8. Marine animal sounds are made up of multiple frequencies
The sound spectrum gives the pressure level at each frequency
Intensity pressure2
SL [dB] = 10 Log10(I/I0)
SL [dB] = 20 Log10(P/P0)

9. Spectrogram shows how sound spectrum changes over time
Worcester & Spindel 2005

10. A fish example of sound use: Atlantic Croaker
Some fish use sound for courting and as a fright response

11. An invertebrate example: snapping shrimp
claw crab
Snapping shrimp make noise to stun their prey.
They create a cavitation bubble that “snaps” as it collapses.

12. Toothed (odonticete) whales
Smaller (1.5 to 17 m long)
Social
Most are not migratory
Chase and capture individual fish, squid, crabs
Echolocate, communicate
Baleen (mysticete) whales
Larger (15 to 30 m long)
Often solitary
Long annual migrations
Feed on aggregations of krill, copepods, small fish
Communicate long-distance

13. Baleen
(mysticete)
whales
Toothed
(odonticete)
whales

14. Baleen whales
Toothed whales
 Toothed whales
 Baleen whales

15. Social calls - sound for communication
Frequency (Hz)
Dolphins live in social groups that stay together 5-10 years. They have “signature whistles” that can be used to recognize individuals at distances of >500 m.
Time (s)

16. Echolocation using echoes from sound pulses or clicks
Whale can determine distance, angle, size, shape, etc. from sound echoes

17. Echolocation frequencies
Toothed whales
Sperm whales form smaller social groups than many toothed whales because their prey (large squid) are more solitary. So they may have to communicate over long distances. Low frequency clicks are for communication, higher frequency clicks (up to 15,000 Hz) for echolocating.
Baleen whales do not echolocate. Why not?
Mellinger 2007

18. 1. They don’t produce high enough frequencies
Baleen whales produce low-frequency sounds with long
wavelengths. Wavelength determines the minimum
echo detection distance.
Frequency f (Hz)
Wavelength λ (m) 10
150
100 15
1,000
1.5
10,000
0.15
100,000
0.015
Food too far away OK
Minimum
echolocation
frequency

19. 2. Baleen whale prey (krill, copepods) are poor acoustic targets
Toothed whale prey:
Squid and large fish
More likely to be solitary
Good acoustic targets
(squid pens and fish swim bladders have density different from water)
Baleen whale prey:
Plankton and small fish
More likely to aggregate
Poorer acoustic targets
(density similar to water)
Toothed whale
prey
Baleen whale
prey

20. A cool invention for listening to whales:
acoustic whale tag
Hydrophones and 3D accelerometers in a waterproof, pressure-resistant case with suction cups
Sneak up on whale, attach D-Tag
Record audio, pitch, roll, heading, depth
Tag pops off, floats to surface 18 h later
Mark Johnson with D-Tag

21. Toothed whale foraging: Beaked whales dive deep to find prey
Natacha Aguilar de Soto
Whales have special adaptations to avoid getting the bends at depth. Bends occur when nitrogen in air in lungs dissolves into blood at increased pressure, then bubbles out in blood when resurfacing. Whales can collapse their lungs during dives to keep air away from lungs so N2 doesn’t dissolve into blood.
Yellow indicates echolocation
Peter Tyack et al.

22. Baleen whale foraging: Right whales dive to bottom of the mixed layer where plankton are most concentrated
Colors: copepod concentration (#/m3)
—: whale trajectory
--: bottom of mixed layer
: Times of visual contacts
: Times of CTD+OPC cast
(OPC = Optical Plankton Counter)
Baumgartner and Mate 2003

23. Blue whales migrate and need to communicate over long distances

24. High-frequency sounds are absorbed more quickly Absorption of sound in SOFAR channel
Because baleen whales have long, solitary migrations, they need to use low frequencies to stay in communication.
Because toothed whales move in groups, they can use high frequencies without losing communication.

25. Transmission loss: Sound signal loss of intensity due to cylindrical spreading, spherical spreading, and absorption
Blue
whale
Dolphins

26. Signal-to-noise ratio (SNR)
SNR in decibels indicates how much of the signal can actually be heard over the background noise level.
For communication, need a minimum SNR of 3 to 5 dB.
A good SNR is 20 to 30 dB.
A negative SNR(dB) indicates no signal gets through.

27. Marine mammal sound levels are generally between 100 and 200 dB
Baleen whales
Toothed whales
Seals, sea lions, and walruses
Manatees and dugongs
Echolocation (toothed whales)
earthquake
rainfall

28. Man-made noise in the ocean
These add constant background noise
Outboard engine
6,300 Hz
Commercial Ship
10 to 20,000 Hz
Airgun
10 to 500 Hz
Up to 232 dB
Low-Frequency Active Sonar
100 to 500 Hz
230 to 240 dB
These are loud enough to damage tissues and cause hearing loss

29. Since the invention of propeller-driven motors (~150 years ago),
Background noise level in the ocean has increased by ~45 dB
Lowest background noise f has dropped from ~100 Hz to ~7 Hz
After motors
~7 Hz
Before motors
~100 Hz
After motors
~75 dB
Before motors
~30 dB

30. Can use transmission-loss curves to calculate the effective communication range
Blue whale song
20 Hz, ~155 dB
Pre-motor noise level
30 dB
Whale song stays
above ambient noise
level for ~2,000 km
e.g. San Diego to Seattle
(area ≈10,000,000 km2 )
Current noise level
75 dB
level for ~60 km
e.g. New Brunswick to NYC
(area ≈10,000 km2)
Blue
whale

31. Range of effective communication for blue whale
singing at 20 Hz and 155 dB
Range before
mid-1800s
Current range
(yes, that tiny speck)

32. Potential effects of man-made sounds on marine mammals
Disruption of feeding, breeding, nursing, acoustic communication and sensing
Psychological and physiological stress
Temporary or permanent hearing loss or impairment
Death from lung hemorrhage or other tissue trauma

33. Noise-induced mass strandings
Mass strandings associated with Navy sonar activity
The Bahamas (2000):
14 beaked whales, 1 spotted dolphin, 2 minke whales
Bleeding in ears
The Canary Islands (2002):
14 beaked whales
Gas bubbles and bleeding in multiple organs
Mass strandings associated with air guns
Tasmania and New Zealand (2004):
208 whales and dolphins
Senegal and Madagascar (2008):
> 200 pilot whales and melon-head whales

34. Captive beluga imitates human voice!
Humans use acoustics to understand whales. Are the whales doing the same to us?
Captive beluga imitates human voice!

35. A great source of information on sound in the ocean: