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I avoid labels when possible, but here goes: SWF, 40'ish, 20 year Navy veteran. I have an inner ham and her name is Ms. Piggy.

Sunday, July 19, 2009

The night I saw sound.

Some of us on FB were speaking about lightning bugs, and it made me think of something else pretty wondrous I've seen I thought I'd share.

I've deduced that the conditions required for this are pretty rare, related to things like the time of year, time of day, the lack of a moon, and thermal gradients in the ocean. I only saw it once, and in 20 years I never heard of another sonar person relating this either.

One night underway in the Indian Ocean as lead sonar technician on watch, I was conducting testing and maintenance on our very high powered sonar. We were actively pinging at full blast into the water and there's something in the order of 300 kilowatts of sound energy being pumped out with every series of pings. These are sent out first as three sequential directed pings of 30 degrees each, left center and right to cover 90 degrees. These are followed by a single 360 degree ping.

At some point I was called to the bridge by the OOD (Officer of the Deck). Once I reported to him, he asked me to look out in front of the ship and tell him what I made of what was going on. It took a few moments for my eyes to finish acclimating to the utterly black night, but I'll never forget what I saw.

Out in the water, like Neptune himself with a huge flashlight; our sonar pings were lighting up the ocean! 3 bright sequential flashes, blue-greenish and perfectly in synch with our pings, each lighting up the water in beams; followed by one dimmer 360 degree flash in synch with the last ping. While I was astounded, I immediately and almost nonchalantly deduced the cause and relayed same to the OOD; can you guess what it was?

After talking to the OOD, I went down to the sonar shack and directed the maintenance team to take a break and meet me on the ships bow, leaving the sonar engaged. Although they are typically our nemesis on a ship, I had friends in engineering so I also called down to the plant and let them know they needed to come see this. Each department's watch team took turns to allow the operators a turn on deck, though I don't think everyone got a chance to see before the phenomenon ended.

Some of us tried to take pictures, but cameras failed to capture it at all. Apparently meant to only be kept in our minds, I think Goddess was trying to show us the wonders she could let us share with our technology were no match for her own.


  1. Electromagnetic refraction involving the salinity and temperature of the water?


  2. The winnah is....

    Jocelyn Jones was the first with the most correct answer when she said at 4:20:

    Oh, you little trickster! Here's my guess: there was some sort of phosphorescent sea creature, a school of them (algae?), that was triggered by the vibrations and phosphoresced in a wave pattern congruent with the signal. If I'm right do I get a prize. If so, I want shoes!

    Bobbie also said as much a bit later so props to you both!

    I was looking for the answer "plankton" since that is the name of the phosphorescent creature that ultimately caused this.

    There is a layer or concentration of sea life called the diurnal layer, so called because it moves up and down in depth due to the cycle of the sun. With the warming of the sun during the day, the diurnal layer is normally close to the surface of the water, it typically sinks well below the surface quickly after sunset. In addition, the layer is normally spread out through a couple hundred feet of depth as the water temperature normally cools gradually with depth.

    So when the layer is near the surface during the day, it is far too bright for us to see this happen; and the layer is also not normally concentrated enough for us to see it at night either. Moonlight and starlight also make it more difficult to see at night.

    While this was happening, I had the sonar team also perform a bathythermograph drop; in other words we sent a probe into the water that measures the temperature down to over 1000 feet.

    The diurnal layer that normally would have spread out and dissipated with nightfall had instead been pushed and concentrated near the surface by a very cold subsurface current not normally present in that local any time of the year. Combined with the moonless, cloud covered sky, we also had a perfectly dark night.

    Erin also mentioned salinity, and I believe it may have had an impact as well because with the exception of the inland oceans, the Indian Ocean is particularly salty. This lends to the water's ability to retain heat.

    Sound is indeed vibration, and just as any other mechanical stimulation can excite the plankton and cause them to phosphoress, the intense sound energy was also doing the same.

    So there you have it, a perfect storm of orgiastic plankton concentrated very close to the surface on a perfectly dark night!