Listening to the song of the sea in Chico, California

Kris Walker, University of California, San Diego
Jeff Mott, California State University, Chico

During the holidays around the dinner table a memorable moment is often shared by dipping your finger in your glass of wine, and circling the rim until the glass starts to “sing.”  This singing occurs because the frequency of the vibrations created by your finger matches the “natural frequency” of vibration for the wine glass.  In this situation, this natural frequency is as easy for us to hear as a tone from a piano.  The ocean is much larger than a wine glass.  But it too has a natural frequency and sings when waves from one direction collide with waves from the opposite direction.  Because wind is constantly creating waves throughout the world’s oceans, waves from different storms eventually collide thousands of miles away, creating the “song of the sea.”

Humans cannot hear the song of the sea.  The ocean’s natural frequency is simply too low for the human ear to detect.  However, special microphones can listen to the ocean quite well.  In fact, the ocean’s natural frequency is so low that these sensors can hear the ocean thousands of miles away, just as you can hear the low-frequency rumbling of thunder from distant lightning.

In October 2010 four microphones were installed at Big Chico Creek Ecological Reserve (BCCER) as part of a NOAA-funded collaboration between the University of California, San Diego and California State University, Chico (Figures 1 and 2).  This group of microphones is part of a larger network of microphones within the western U.S. states.  The project has two goals.  The first goal is to use these microphones to locate the source of the ocean sound in the eastern Pacific Ocean.  Just as having two ears allows you to pinpoint the location of the ringing wine glass with your eyes closed, having more than one microphone allows scientists to locate where the ocean sound is coming from.

The primary source of ocean wave forecasts for the inshore and offshore Pacific is NOAA.  These forecasts come from models of the ocean waves, which are created in part by the heights of waves measured by buoys.  Verifying the accuracy of these models is important because commercial and recreational human activities both near the coast and hundreds of miles off the coast rely on these models to make important decisions.  One could put hundreds of thousands of buoys in the ocean to verify that these models are accurate, but that would be prohibitively expensive.  However, these models can predict where ocean sound will come from.  Therefore, the second goal of this project is to verify that the NOAA wave models are accurate by comparing the observed sound locations to the predicted ones.

This project is a work in progress. Preliminary results were presented at the American Geophysical Union meeting in San Francisco in December 2010.

There are many people who assisted in this project.  But we want to especially thank Brendon Armstrong (1987-2011).  Brendon prepared BCCER for the microphones, help install them, and was the primary caretaker.  His dedication and hard work was critical to the success of this project, and we will miss him dearly.

Tagged as: American Geophysical Union, BCCER listen to the sound of the ocean, BCCER sound project, Brendon Armstrong, California State University Chico, Jeftt Mott, Kris Walker, NOAA, song of the sea, University of Caifornia San Diego