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Sound Bytes: Why We Look at Sound, and How You Can Help!

September 23, 2022

…When listening isn’t the only option

Cory Hom-Weaver looking up and to the side while holding her finger to her headphones over her head. In the background there is a framed poster of whales of the world Cory Hom-Weaver listens to whale songs while at SWFSC. Credit: NOAA Fisheries / Cory Hom-Weaver

 

Sound is fundamentally important for exploring our environment. And as you have learned from this blog series, sound is crucial if you are a whale or dolphin and you live in the ocean (which often has poor visibility). But as you have also seen throughout this blog, we as bio-acousticians, often transform sound into visual representations called spectrograms or wave forms. But why?

 

Well, humans have evolved to depend very heavily on sight as a primary sensory input. A large part of our brain is dedicated to processing visual information, so naturally we are better at interpreting images than sounds. In fact, the average human can only detect sounds that fall between 20Hz and 20kHz. Very few of us have good enough hearing to cover that entire range. If you want to see how well you hear, check out this link. It plays all of the frequencies in the audible human range. How well do your ears measure up?

 

An infographic of the sound frequency vs the electromagnetic spectrum. On the x axis is sound frequency and on the y axis is light frequency. The middle of the graphic depicts the tiny portion that humans can see and hear on the frequency scale.
“The Sliver of Perception.” by Abstruse Goose is licensed under CC BY-NC 3.0 US
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Many sounds that whales and dolphins make are out of our hearing range. Let's take an echolocation click as an example. These signals are short in duration, and broadband in nature (meaning they span a large frequency range). While the frequency range of an echolocation click varies by species, many clicks are ultrasonic and well above 20 kHz, meaning that we cannot hear them. But when we turn that sound into an image, we sure can see the echolocation clicks. Check out the example of beaked whale echolocation clicks below.

 

Spectrogram of beaked whale echolocation clicks. The x-axis represents time and the y axis represents frequency. You can see that the energy of the click spans from approximately 40kHz to 90kHz, which is out of our hearing range.
Spectrogram of beaked whale echolocation clicks. The x-axis represents time and the y axis represents frequency. You can see that the energy of the click spans from approximately 40kHz to 90kHz, which is out of our hearing range. Credit: NOAA Fisheries / Jay Barlow and Cory Hom-Weaver.

 

What about a blue whale? Yep, you guessed it, we can’t hear them either—well, most of us can’t. They are one of the loudest animals on the planet, but they vocalize in the infrasonic frequency range (too low for humans to hear). But the cool thing about blue whales is that recorders can pick them up hundreds of miles away from where the animal is vocalizing. And we can still see their sounds even though we cannot hear them.

 

A blue whale coming to the surface to breathe. Here you can just see the back breaking the water's surface.
A blue whale surfacing to breathe. Credit: NOAA Fisheries/ Cory Hom-Weaver

 

Help Us Identify Sounds

Because we are able to process visual information so well, humans are really good at identifying patterns in visual data. That is why the Southwest Acoustics Ecology Lab needs your help! We collect a ton of data every year, and with big data there are often big challenges. We need you to help us identify sounds in some of those data. 

 

We are in the process of putting together a Zooniverse (citizen science) project called Ocean Voices and we need beta testers for this project. We ask users to look at and listen to a sound and identify if there is ship noise or humpback whale calls in the sound clip (don’t worry, they are both audible to humans). Do you think you could tell the difference between humpback whales and vessel noise?  

 

What we need more than anything at the moment is feedback to make our site better for the general public. If you have any comments or questions please feel free to leave it in the support section of the project. Thank you for your help! 

 

Learn more and get started! 

 


 

 

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Last updated by Southwest Fisheries Science Center on September 29, 2022