To be honest, I am not really sure how fish hear fireworks. If you’re curious, which I hope by the end of this post you will be, you should take a look.
I had wanted to hear and record fireworks and boat traffic on a lake from an underwater perspective for a while. There are three man-made reservoirs within minutes of my home. Pontoon boats, jet skies and fishing boats zigzag back and forth creating plenty of undesirable noise. With a pair of hydrophones and a friend’s access to a private dock, I drove out this past Memorial Day weekend to Charles Mill Lake in north central Ohio. I recorded fireworks here last year. The long, decaying echoes the blasts create are tremendous. I wondered if they could be heard underwater as well.
The rickety wooden dock screeches and bends from every footstep taken and each wave that passes by it. I stretched out microphone cables along its entire length in order to get the best stereo separation possible. I then set up a recorder to capture above-water sound, and took a wobbly seat to watch the show.
As anticipated, the sound of fireworks underwater is not all that different than what we hear as we’re being bit by mosquitos above water. Somewhat muffled, but still loud. It’s got to be frightfully, if not painfully loud down there for fish and other aquatic life as fireworks blast above their heads.
On a larger scale, there was a scientific paper put out not too many years ago postulating that the sound of the world’s oceans were louder in the 1800’s than they are now due to whale noise. The planet had more whales then of course. The sound of a lightning strike heard underwater, or the sounds of pistol shrimp eating are also extremely loud. But these are natural sounds. Sounds that fit into the acoustical slots animals evolved with. On the contrary, the machine noise our boats and our ships and our oil exploration rigs make has become, to the detriment of marine life, the dominant sound in our oceans.
What you hear in the sound excerpt below, taken from the original 17-minute recording, is a mix of two recordings capturing the finale simultaneously. I then synced both in post, with an abrupt dropout of the above-water recording 15 seconds in. I then bring the ambient sound back up toward the end where you can faintly hear a happy boating crowd cheering and honking their horns in approval. (See screenshot below).
For further reading on the subject of noise pollution in the world’s oceans:
Since writing this blog post, I have had several email exchanges with Michael Stocker, director of Ocean Conservation Research, and author of Hear Where We Are: Sound Ecology, And Sense Of Place. Looking into the phenomenology of sound perception is the cornerstone of his work as he puts it. He has been kind enough to share some of his concepts with me.
“Fish hearing is not calibrated to human hearing”, says Stocker. “There is ample reason to believe that fishes sensitivity to impulse sounds might be greater than their sensitivity to continuous sounds. But it is good to establish some relativistic benchmark,” he added. I wondered if an impulse sound such as a firework, or a sonar blast, or a lightning strike, or an underwater pile driver, would disturb a fish more than the continuous noise of shipping lane traffic or an already-established offshore wind turbine, sort of like how some humans get used to the train noise out their bedroom window. “It is a bit more complicated than this, said Stocker. But in an environment where visibility is often really limited, and where everything from lightening strikes to earthquakes can be heard for thousands of miles, and the most pernicious or most valuable sound needs to be heard equally well in crashing and calm seas, volume is not necessarily the most important perceptual characteristic. So from a phenomenological as well as a physiological standpoint, signal rise time is much more important than amplitude. There is no clear evidence of “habituation” in the cognitive sense, but adaptation may include the ability to sort out signals in the time domain where amplitude or frequency characteristics might otherwise mask important sounds.”
Stocker goes on to write, “There is a 65dB attenuation at the air/water boundary layer, but that doesn’t mean that it calibrates out to how fish hear the noise because water transmits sound intensity much better than air.” Ultimately he says it comes down to two things; how much energy is in the system (some math involved) and what the fish hear (some speculation on our part). “Because while we know some fish hearing thresholds, we only know these in the pressure domain, not particle velocity. And my suspicions are that fishes may be much more sensitive to coherent sounds that we understand.”
Now to sort through everything he said, examine his book links, and find more scientific work on the subject. Hydrophones definitely open up a whole new world of listening, and thinking.
Also, an Italian pyrotechnics company has produced a silent firework that in theory could prevent the stressful and disorienting effects the loud bangs have on everything from your family dog, to a special-needs child, to that lowly fish in the sea. See a link to a story about this here.
And as a side geek note, if you’re interested in how I sync my two recorders, I purchased a D-Day cricket at the National WWII Museum in New Orleans a couple of years ago specifically for this purpose. The sound it makes is loud and quick, better than a handclap. It allows me to easily see spikes on my waveforms to match the tracks. William Hurt used one to great effect in the show Goliath.