S1 E1: Ocean Acoustics with Shima Abadi and Rachel Aronson

Shima Abadi is Director of the Ocean Data Lab and an associate professor at the UW School of Oceanography. She also holds a joint appointment as an associate professor in the Mechanical Engineering Program at UW Bothell's School of Science, Technology, Engineering & Math (STEM).

Abadi’s intricate research primarily focuses on ocean acoustical signal processing, noise propagation in the ocean, machine learning in analyzing ocean ambient noise, and developing algorithms for analyzing large data sets collected by underwater networks.

In this episode, Abadi discusses ocean acoustics and analyzing data to understand the soundscape of underwater environments.

Rachel Aronson holds an M.M.A. from the University of Washington’s School of Marine and Environmental Affairs and leads the Quiet Sound program. As a student, Aronson received support from the Linda J. Maxson Endowment in Marine Policy and the School of Marine and Environmental Affairs Graduate Student Fellowship Fund.

In this episode, Aronson shares about the collaborative program dedicated to reducing noise impacts to Southern Resident Killer Whales from large commercial vessels in Puget Sound.

Orca recordings courtesy of nps.gov.

https://environment.uw.edu/podcast

Chapters

• 0:30 Shima Abadi
• 9:29 Rachel Aronson

Transcript

00;00;00;07 - 00;00;11;07
Shima Abadi
So by long, long term ocean ambient noise analysis, we can understand the whole seasonal pattern. And also the long term trend is the ocean getting noisier or not?

00;00;12;19 - 00;00;34;27
Sarah Smith
From the University of Washington College of the Environment, this is FieldSound. 

00;00;35;21 - 00;01;00;09
Shima Abadi
My name is Shima Abadi. I'm an associate professor in the School of Oceanography. I work in ocean acoustics, underwater acoustics. So anything that relates to sound and how sound interacts with the ocean boundaries, like the ocean's surface, ocean bottom and how it propagates... and what can we learn about it? What can we learn about the ocean environment just by listening to the ambient noise?

00;01;01;11 - 00;01;38;09
Shima Abadi
So that's that's what I do. Sound propagation underwater is is complex because the speed of sound is not constant in air. Speed of sound is almost constant, and sound travels in a straight lines, but underwater, because it's a stratified environment, speed of sound is a function of depth is a function of location. It's a function of time. Imagine that you are in a jungle or forest or some unknown area that you don't know anything about the environment.

00;01;38;19 - 00;02;08;12
Shima Abadi
You're just there and just listen. You just listen and just try to understand where you are based on the sound that you hear. Like if you are in a jungle, you can hear monkeys, for example, you can hear goats, you can hear birds, you can hear rain, you can hear wind. And just by processing these different sound that you can hear and you can classify, technically, you have an idea about where you are and you can navigate.

00;02;08;12 - 00;02;18;06
Shima Abadi
So it's exactly like that in the ocean. And we just have a hydrophone and we just listen.

00;02;18;06 - 00;02;34;14
Sarah Smith
Shima Abadi is conducting long term studies of ocean ambient noise alongside researchers from the UW School of Oceanography. As director of the Ocean Data Lab, the team records ambient ocean sound for data analysis using hydrophones and a fiber optic cables.

00;02;35;12 - 00;02;58;01
Shima Abadi
So in traditional ocean acoustics, we measure data by hydrophones, and that's a single point measurement. We deploy a hydrophone, which is technically a microphone that is able to record audio signals underwater and we deploy at any location that we want. We can collect data for a long time and it can be cabled. We can get data in real time or we can get the data wants to retrieve things from it.

00;02;58;10 - 00;03;25;15
Shima Abadi
But it's a single point measurement. And if we need more data points, we need to add more hydrophones, hydrophones, convert pressure, pressure change to signal that we can see by fiber optic cables they measure straight or stream rate along the cables. So it's a little bit different terms of the physics that we use, but both of them are capable of showing any pressure disturbance like sound.

00;03;25;15 - 00;03;50;20
Shima Abadi
It's important to measure the speed of sound, to understand how sound propagates in the ocean. Sound is not doesn't propagate in the straight lines. It's more like a curvature. So technically you can imagine if you have a sound source in the middle of the water column, the energy that goes up toward the surface bends away from the surface, and the energy that goes toward the sea floor, bends away from the seafloor and comes back up.

00;03;50;29 - 00;04;19;09
Shima Abadi
And this trend continues for very long distances. And that's why sound is the only way that we can use to probe the ocean in long distances. The ocean is a noisy environment because it's it's it's an environment that is technically confined by the ocean surface and ocean. It so sound echoes, stays in the water column for a long time of world resources.

00;04;19;24 - 00;04;41;03
Shima Abadi
So we have a hydrophone. And if we listen, we can hear rain, we can we can understand if it's heavy rain or light rain. Just just by listening to that, just by the sound analysis where we can hear wind at the surface, we can hear marine mammals. So are they close to coming close or they're getting away from us?

00;04;41;03 - 00;04;58;27
Shima Abadi
They can hear ships, we can hear earthquakes. If they are close to a volcano, we can hear volcano eruption. So by long, long term ocean ambient noise analysis, we can understand the whole seasonal pattern. And also the long term trend. Is the ocean getting noisier or.

00;05;03;11 - 00;05;19;10
Sarah Smith
The patterns identified in the ocean. Acoustic data helps inform a variety of ocean research disciplines. The ocean is an area of unknowns. Only 5% of the ocean has been explored and charted by humans.

00;05;20;02 - 00;05;45;28
Shima Abadi
Well, most of the time we collect data, long term data, and then we come back when we start processing and we don't know where it's coming from. There are some so we know. We know something about some specific sources of sound in the ocean, but we don't know everything. So a lot of times we collect something and we have no idea where it's coming from or what is causing that noise.

00;05;46;05 - 00;06;04;24
Shima Abadi
So under there, fully understand ocean, ocean ambient noise is something that requires a lot of a lot of studies and a lot of research and a lot of new techniques. We are not there like you're physically not there to know or to hear. Even if we were there, there are some frequencies that we cannot hear. So we don't know.

00;06;05;02 - 00;06;14;11
Shima Abadi
We don't know everything and useful. So there are some times that I look at the data I see. I don't know.

00;06;14;11 - 00;06;29;23
Sarah Smith
"I don't know" is a powerful statement for science. It can often spur more questions and in turn more answers, often with unexpected results. A multitude of possibilities.

00;06;30;29 - 00;06;58;07
Shima Abadi
Well, when I started working with fiber optic cable, so the technique is called distributed acoustic sensing. Or in short, we say that when I started looking at the data, it was a vital moment because we were able to record a single vocalization for over 60 kilometer of the cable. So it's it's it's a huge amount of data, and it's the first time that we can record in this scale.

00;06;58;26 - 00;07;08;27
Shima Abadi
So there are so many things that we can do. And this technology is very early stage. So we are trying to understand the limitations, trying to understand the capabilities.

00;07;10;02 - 00;07;15;25
Sarah Smith
One area where the data from ocean acoustics is being applied is the effects of noise on marine mammals.

00;07;16;15 - 00;07;39;23
Shima Abadi
We can easily see when animals are coming close, they're vocalizing or this is the this is the mating season, this is this is the feeding season because they have different types of calls. We successfully showed that fiber optic cables can record low frequency species like fin whales and blue whales. They show up in off the coast of Washington and Oregon.

00;07;39;29 - 00;08;07;05
Shima Abadi
They late fall and they vocalize continuously until winter, maybe early spring. So the whole band that they vocalize is getting noisier. And there's a seasonal pattern associated to their vocalization and just trying to understand this contribution as a function of location. So how how it changes from hydrophones that we have closer to the shore compared to the hydrophones that we have?

00;08;07;05 - 00;08;36;19
Shima Abadi
Offshore orcas are higher frequency species. They generate higher frequency seas and boats and ships can generate broadband signals. So they have low frequency, high frequencies too. When when we have ships in the area, one thing that happens is that because the ship is generating sound this so that that part of the ocean gets a little bit, it gets noisier, the noise level goes above the average and it masks their vocalization.

00;08;36;27 - 00;08;58;11
Shima Abadi
So if they are trying to send a signal maybe to another orca or to find food or something, they cannot do that. Recently, I conducted a test in Puget Sound to see if we can measure higher frequency sound and it shows that successfully we can measure higher frequency sound. But now it's time to explore higher frequencies. Species can be locate them.

00;08;58;11 - 00;09;16;11
Shima Abadi
Can we learn about their behavior, especially in an area that has a lot of ship traffic knowing because we can do that in real time with fiber optic cables. We have access to the data in real time. So it's important to know their location in response to ship noise or other than.

00;09;16;15 - 00;09;36;13
Rachel Aronson
Of course, we know from scientific research that when a vessel is nearby they will stop foraging.

00;09;37;00 - 00;09;43;02
Sarah Smith
Rachel Aronson a UW School of Marine and Environmental Affairs alum leads the Quiet Sound program.

00;09;43;23 - 00;10;17;13
Rachel Aronson
And part of why that is, is that large vessels actually most vessels emit underwater noise in the same frequencies that the Southern resident killer whales use to hunt and to communicate. And so when they hunt those fish, they use a process called echolocation. They they send out a squeak that your house bounces back off of fish. And then they do it with fishers, because when you're underwater, life becomes useless pretty quickly as a way to find out what your players, They also need to communicate with each other.

00;10;17;13 - 00;10;27;01
Rachel Aronson
They have a close knit social structure. They spend their whole lives with their pods, their family, and so they need to know where the other whales are. And sometimes they hunt collaboratively.

00;10;27;01 - 00;10;35;05
Sarah Smith
Quiet Sound is a collaborative program to reduce noise impacts to Southern resident killer whales from large commercial vessels.

00;10;35;24 - 00;11;03;21
Rachel Aronson
We put forward scientific data driven recommendations on how ships can behave on the water to mitigate the impact on orcas. We build the relationships to support those actions and provide all the knowledge and tools that mariners need. And then the Mariners go out and ship better among the orcas. So we're not a state agency. We can't set regulations, but we can help people take action much more quickly than if we relying on a regulatory process.

00;11;04;08 - 00;11;13;21
Sarah Smith
Human impacts in the ocean aren't limited to boats and ocean vessels. Earth's changing climate and warming waters create complex challenges in the ocean environment.

00;11;14;06 - 00;11;40;05
Shima Abadi
There is a channel, there is a depth, there's a layer in the ocean that's sound, can travel really long distances without any interaction with the ocean surface. At ocean bottom, that layer is called the sound channel or so forth channel and animals, they know about that. They know about the depth, the optimum depth that they can vocalize and their vocalization can go longer distances in the ocean.

00;11;40;05 - 00;12;06;20
Shima Abadi
Temperature impacts the speed of sound and the speed of sounds is very important for underwater acoustics. If the speed of sound changes, this optimum depth will change and in higher latitude, this optimum depth is coming closer to the surface. And this change is happening so fast it's even faster than the life cycle of one generation. So they cannot adapt to that change.

00;12;06;29 - 00;12;28;21
Shima Abadi
This is going to have serious impact on their feeding behavior and mating and all the other functions that they do.

00;12;28;21 - 00;12;41;29
Sarah Smith
Scientists can't always be there in the ocean looking for patterns in the ocean. Soundscape creates opportunity for understanding and connection to the world around us.

00;12;41;29 - 00;13;09;24
Shima Abadi
I believe the ocean science is is changing in a way, in a way that the way we look at the way we look at the problem, because these days we have access to high computations like high power computers and cloud computing. So a combination of ocean science and data science can help us discover a lot of things about the ocean.

00;13;09;24 - 00;13;24;12
Shima Abadi
So in ocean acoustics, we have people from different backgrounds. And that's the beauty of this field, because we can work with each other and we can learn from each other and we can add our skills, will add power to how we process the data and how we learn about the ocean.

00;13;25;20 - 00;13;50;22
Sarah Smith
A special thanks to our guests, Shima Abadi and Rachel Aronson. You can learn more about Abadi's research and the University of Washington College of the Environment by clicking the link in this episode description or by visiting our website environment.uw.edu. To learn more about Aaronson's work at Quiet Sound, visit quietsound.org

00;13;50;22 - 00;13;58;09
Sarah Smith
From all of us at Field Sound. Thanks for listening.