July 8 – Can You Hear Me Now?

Today’s factismal: The hydrophone was invented as a way of locating icebergs.

Necessity, they say, is the mother of invention. And nothing illustrates necessity like a disaster. That’s what happened in 1912 when the RMS Titanic hit an iceberg and sank, killing 1,502 people. Though many focused on the need for improved safety measures on ocean liners so that more would survive after a collision, one person looked (or listened) for a way to locate icebergs before they became a problem. Reginald Fessenden knew that you could use the echoes in a room to keep yourself from running into the walls, even if it was pitch dark. And so he decided to see if he could apply that simple idea to finding icebergs in the ocean.

The world's first hydrophone (Image courtesy IEEE)

The world’s first hydrophone
(Image courtesy IEEE)

Using a metal plate and a simple radio circuit, Fessenden was able to create a device that both sent out a simple tone and listened for the echoes. By timing the difference between when the tone was sent out and when it returned, the operator could determine how far away an object was. And by simply listening, the operator could hear how noisy the ocean truly was.

Whales like this have been using natural hydrophones for more than a million years (My camera)

Whales like this have been using natural hydrophones for more than a million years
(My camera)

And, of all of the outcomes of the new invention, that was the most surprising. People had thought of the ocean depths as being silent places. Instead, they were filled with a cacophony of noises. The rumble of the waves overhead. The slow susurrus of underwater streams. And, most amazing of all, the click and chatter of the animals, from the deep boom of the aptly-named drum fish to the squeak and chirp of dolphins and other whales who had discovered Fessenden’s secret more than a million years before the Titanic.

If you’d like to do a little listening of your own (and maybe slip in some citizen science while you are at it), then go to the Salish Sea hydrophone network where you can listen to hydrophones placed around Puget Sound. And if you happen to hear an orca or two, let the scientists know about it, OK? They are trying to learn more about orca behavior in the area and need your help to do it!

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