1 of 45

How noise pollution impacts communication in whales and dolphins

Laela Sayigh

Woods Hole Oceanographic Institution

Hampshire College

Mary Carla Curran

Savannah State University

1

29 August 2023

2 of 45

Purpose

This presentation was created as part of an Ocean Communication Fellowship in 2021-2022 awarded to Dr. Laela Sayigh at the Woods Hole Oceanographic Institution.
It is designed to be a stand-alone presentation that teachers can use to instruct students about impacts of noise pollution on cetaceans.
This activity is suitable for the visually impaired as students can learn about vocalizations of marine mammals using the sense of sound.
Mention of certain equipment or software programming is not an endorsement of any products.

2

29 August 2023

3 of 45

Purpose

Dr. Laela Sayigh is a Research Specialist in the Biology Department at the Woods Hole Oceanographic Institution, and an Associate Professor at Hampshire College. Her research focuses on communication in whales and dolphins.

Dr. Mary Carla Curran is a Retired Professor Emerita in the Department of Marine and Environmental Sciences at Savannah State University and manager of Broader Impacts, LLC. She has extensive experience translating scientific research into peer-reviewed K-12 activities that often include modifications for the visually impaired. Her areas of research include fish biology, parasite-host interactions, and estuarine ecology.

About the authors

3

29 August 2023

4 of 45

CETACEANS

Sound is their primary mode of communication

5 of 45

Almost all sunlight is absorbed within 200 m of the ocean’s surface

ILLUSTRATION BY STEVE SKELTON FOR TIME FOR KIDS

5

29 August 2023

6 of 45

But sound travels faster and farther in water than in air

A fin or blue whale near Newfoundland, Canada could potentially hear a whale singing in Bermuda (about 2500 km)!

6

29 August 2023

7 of 45

Useful words for describing sound:

Amplitude = loudness

Frequency = pitch

High-frequency = Shorter Wavelength

Low-frequency = Longer Wavelength

7

29 August 2023

8 of 45

Cetacean Vocal Ranges

Fin whale

20 Hz Pulses

Dolphins

Whistles & clicks

Harbor porpoise

Ultrasonic clicks

Frequency (Hz)

Infrasonic

Ultrasonic

1

10

100

1000

10,000

100,000

1000,000

Human Hearing

Sperm whale

Clicks

Graphics courtesy of R. Swift

Cetaceans are most sensitive to sounds within their vocal range.

Different species have very different vocal ranges with the largest whales producing very low frequency sound and the smaller dolphins and porpoises producing higher frequency whistles and clicks.

Frequency is analogous to pitch. Humans can hear sounds in the middle frequency range, from about 20 Hz to 20,000 Hz, depending on our age (hearing range decreases as you get older).

Some marine mammal sounds are below human hearing range, or “infrasonic”, like the sounds made by fin and blue whales. Others are “ultrasonic” or above human hearing range, like the clicks of harbor porpoises. The only way we can listen to recordings of infrasonic or ultrasonic sounds is by speeding up or slowing down the recordings, which changes the pitch as well.

9 of 45

Noise pollution is a major problem for cetaceans!

What are some of the sources of this pollution?

9

29 August 2023

10 of 45

Commercial Fishing Vessels

Whale-watching Vessels

Recreational Boaters

Tankers

Industrial: Oil, natural gas, wind farms, sonar

Ocean noise has increased at least a hundredfold since 1960

Noise pollution is a major problem for cetaceans!

What are some of the sources of this pollution?

10

29 August 2023

11 of 45

Sources of noise in the ocean

11

29 August 2023

12 of 45

How do we record cetacean sounds?

Bottom mounted recorders
Real-time buoys
Towed arrays/ hydrophones
Acoustic tags on animals (DTAG)
Autonomous gliders

Bottom mounted recorder

Towed arrays/hydrophones

Real-time buoys

DTAGs

Autonomous gliders

Bottom-mounted recorders

12

29 August 2023

13 of 45

How do we analyze cetacean sounds?�Spectrograms

Like musical notation

Spectrograms allow us to see sounds that we can’t hear

Normal speed

Slowed down 4 times

13

29 August 2023

So once we’ve recorded cetacean sounds, how do we analyze them? We usually analyze them visually, using plots called spectrograms. These are very similar to musical notation, with frequency on the y axis and time on the x axis. Spectrograms allow us to see sounds that we can’t hear, including subtle inflections in sounds like you can see in the spectrogram of a dolphin whistle in the upper right. That whistle is so high frequency that none of us would be able to hear it if I played it (Remember that human hearing ranges from about 20Hz to 20kHz). But, we lose our high frequency hearing as we get older, so even this lower frequency whistle shown in the lower left can be very hard for people to hear, depending on your age! For example, I can’t hear it at all played at normal speed.

Teachers, you can play this sound and ask students to raise their hands if they hear it. Most if not all will. Then you can play it slowed down 4 times so it will be audible to everyone (including teachers). Before moving onto the next slide, you can point out that 440 Hz, which is the note the orchestra tunes at, is way down almost on the x axis of these images (since they are in kilohertz, or thousands of Hertz). The next slide shows a blue whale sound, which is much lower frequency, and 440Hz is visible on the y axis.

14 of 45

Blue whale sound (sped up 4x)

14

29 August 2023

15 of 45

Figures: B. Southall, US NOAA & C. Clark, Cornell University

Frequency overlap

between marine

animal communication

and shipping noise

Different marine species are impacted by different types of noise

15

29 August 2023

16 of 45

Blue whale sound with ship noise

Sped up 4 times

Mixed with ship noise

16

29 August 2023

17 of 45

Acoustic masking of right whale sounds

Michael Thompson

Acoustic masking – when noise covers or “masks” animal signals

Ship tracks for one month

17

29 August 2023

18 of 45

Typically studies of masking focus only on whether a signal is detectable or not
Communication masking is when signals are audible but not “understandable”
The focus of our activity is on communication masking, using dolphin signature whistles as examples

Acoustic masking – when noise covers or “masks” animal signals

18

29 August 2023

19 of 45

Dolphin signature whistles –”name” like sounds!

19

29 August 2023

20 of 45

20

29 August 2023

21 of 45

Figures: B. Southall, US NOAA & C. Clark, Cornell University

Frequency overlap

between marine

animal communication

and shipping noise

We talked about how baleen whales are particularly affected by shipping noise

21

29 August 2023

22 of 45

Recreational boats cover a greater range of frequencies than do ships

Thus, recreational boat noise can mask dolphin signature whistles

Recreational boat

Commercial ship

22

29 August 2023

However, recreational boats, which are ubiquitous in the Sarasota Bay area (and many other areas where coastal dolphins live), cover a greater range of frequencies than do ships. The upper left image shows the wide range of frequencies covered by a recreational boat, whereas the bottom image shows a commercial ship (notice that the blackness, which is related to the intensity of sound, covers most of the upper image but mostly the lower portion (meaning lower frequencies) in the lower image). Although some of this is related to distance, that is, if you were right next to a commercial ship you would hear more high frequencies, and if you were further away from a recreational boat, you would hear less of the high frequencies, we do know that dolphins in the Sarasota bay area are exposed to many recreational boats at close proximity every day. Note: no sounds are included on this slide, these are visual representations of how much of the frequency range is affected by noise.

23 of 45

CZS-SDRP NMFS Permit #20455.

Dolphin sounds courtesy of Frants Jensen, WHOI

Example of whistles being masked by recreational boating noise

23

29 August 2023

24 of 45

We will explore features of dolphin signature whistles that might make them more identifiable in noise (not just detectable)
We will first experiment with sonic versions of names!

Communication masking

24

29 August 2023

25 of 45

Student names were sonified with the program LoggerPro, which allowed us to assign one of 26 unique notes to each of the 26 letters of the alphabet
The following three slides each contain spectrograms and sounds of example names; you can view all or some, and some can be played as a “quiz”

Sonifying student names

25

29 August 2023

26 of 45

Sonic versions of names

Amelia

Amy

Quiz! 1) 2) 3) 4) 5)

Reagan

Abigail

Wassila

Alexander

Alison

Amanda

Ashley

Emily

Evan

Hailey

Isabelle

Anna

Caitlin

Claire

Genevieve

26

29 August 2023

27 of 45

Sonic versions of names

James

Jessica

Morgan

Quiz! 1) 2) 3) 4)

Jack

Jake

Jonathan

Jack

Jordan

Justin

Kaitlyn

Lauren

Maggie

Melanie

Michael

Nadia

27

29 August 2023

28 of 45

Sonic versions of names

Quiz! 1) 2) 3) 4)

Stephanie

Nancy

Timothy

Tommy

Nora

Ruby

Nancy

Sophia

Thomas

Timothy

Tommy

William

28

29 August 2023

29 of 45

Were any of them easier to tell apart?�If so, why?

29

29 August 2023

30 of 45

The following 3 slides show the same spectrograms of student names as before, but they have now been combined with boat noise

Combining sonified names with noise

30

29 August 2023

31 of 45

Names combined with boat noise

Amelia

Amy

Quiz! 1) 2) 3) 4) 5)

Reagan

Abigail

Wassila

Alexander

Alison

Amanda

Ashley

Emily

Evan

Hailey

Isabelle

Anna

Caitlin

Claire

Genevieve

31

29 August 2023

32 of 45

Names combined with boat noise

James

Jessica

Morgan

Quiz! 1) 2) 3) 4)

Jack

Jake

Jonathan

Jack

Jordan

Justin

Kaitlyn

Lauren

Maggie

Melanie

Michael

Nadia

32

29 August 2023

33 of 45

Names combined with boat noise

Quiz! 1) 2) 3) 4)

Stephanie

Nancy

Timothy

Tommy

Nora

Ruby

Nancy

Sophia

Thomas

Timothy

Tommy

William

33

29 August 2023

34 of 45

What are some features of the sounds that could make them easier to distinguish?

34

29 August 2023

35 of 45

What are some features of the sounds that could make them easier to distinguish?

Louder
Longer/shorter
Larger frequency range
Higher frequencies that extend out of the boat noise
Features that might be audible through noise, such as a lot of ups and downs

In some cases, maybe you knew there was a sound, but couldn’t identify which one
This is communication masking – sound is detectible but not understandable

35

29 August 2023

36 of 45

Let’s explore some dolphin whistle features. Which do you think could be heard better over noise? Why?

36

29 August 2023

37 of 45

Now I will play them with boat noise and you tell me which is which

37

29 August 2023

38 of 45

Look at these images of dolphin whistles with boat noise. Which do you think a dolphin could hear better? Why?

38

29 August 2023

39 of 45

Examples of unusual features that could increase audibility in noise

Steps

Concurrent pulses

39

29 August 2023

40 of 45

What might be some strategies dolphins can use to make their signature whistles heard by other dolphins?�

40

29 August 2023

41 of 45

What might be some strategies dolphins can use to make their signature whistles heard by other dolphins?�

Whistle more loudly
Make longer whistles
Make more repetitions of their whistle
Produce whistles that have a large frequency range
Produce whistles that contain frequencies higher than boat noise
Produce unusual features that might be audible through noise

41

29 August 2023

42 of 45

Different types of noise impact whistles differently – for example pile driving

42

29 August 2023

43 of 45

Pulsed sounds vs. whistles – with and without pile drive sounds

43

29 August 2023

44 of 45

Summary

Noise is a pollutant that has major impacts on whales and dolphins, since they rely on sound for communication
When noise prevents animals from hearing sounds, it is called masking
Communication masking is when the function of the sound is lost, even if the sound is still detectable
Some dolphin whistles have features that make them more identifiable in noise
Different types of noise vary in how they impact different dolphin sound types

44

29 August 2023

45 of 45

This work was supported by an Ocean Communications Fellowship Award (27994.01) from the Woods Hole Oceanographic Institution. We would like to specifically acknowledge The Supporters of the Ocean Communications Initiative and the Coastal Kealy Family Foundation.

Some of the content and slides were provided by Genevieve Davis at NOAA’s Northeast Fisheries Science Center and Grace Simpkins at Woods Hole Sea Grant. Most cetacean images in this presentation were created by Uko Gorter, and were used with his permission. These images were acquired with prior funding from Woods Hole Sea Grant.

A number of teachers allowed us to test the prototype of this activity and obtain feedback before finalizing the presentation. We would like to thank Kate Fraser and Kris Bayne at the Perkins School for the Blind, John Lee at Norfolk County Agricultural High School, and Nancy Young at Acton Boxborough Regional High School. Thanks also to Massachusetts Marine Educators for allowing us to present this activity during a workshop in April 2022 at their annual meeting.

Acknowledgments

45

29 August 2023