Whales can’t hear each other in the noisy ocean. This inventor has a solution 200 years in the making.
Popular Science...
When most people think of noise pollution, the image conjured up is one of concrete buildings and crowded streets bursting with beeping car horns and screeching industrial tools. But there’s another flavor of noise pollution happening underwater, across the world’s oceans, and it’s taking an even worse toll on its inhabitants.
The constant hum from human-made inventions (think massive shipping boats, deep-sea mining, and offshore oil rigs) has radically transformed the sound of the ocean. An environment once dense with complex whale songs and subtle marine communication now sounds like something closer to a never-ending heavy metal show.
Whales are particularly challenged by the cacophony. When it’s quiet, these marine giants can hear each other’s calls from hundreds of miles away. Parsing those calls is fundamental to how they coordinate, mate, forage, and survive day to day. The problem is that the same low-frequency range they use to communicate (roughly between 20-300 Hertz) overlaps with the noise generated by commercial shipping. It might not sound like much to humans on the surface, but that’s because we’re not getting the full experience.
“Imagine somebody jackhammering outside your window for months at a time,” University of New Hampshire acoustic ecologist and ocean noise pollution expert Michelle Fournet tells Popular Science. “It hurts your ears. It is painfully loud.”
The impacts are striking. Researchers found that every decibel increase in the maximum level of noise surrounding orcas made them four percent more likely to search for food while simultaneously giving them a 12.5 percent lower chance of actually catching a fish they chased. Fournet described this disruption as akin to someone seeing the world around them normally, and then suddenly having a floodlight beamed in their eyes, all day, every day.
When it comes to boats, the primary culprit for much of this disruptive noise is something called cavitation, which comes from their propellers. Cavitation occurs when a boat’s screw-shaped propeller spins so fast that it creates a trail of tiny bubbles right behind it. Those bubbles contain stored energy that, when they pop, releases sharp shockwaves, creating a hissing or crackling sound. A single propeller can generate and pop millions of these little bubbles per second. That all quickly adds up.
A Detroit-based company called Sharrow Marine believes it may be working towards a solution. Over the past decade, the company has advanced a completely new type of propeller design that results in a radically quieter boat. Rather than using blades with free-hanging tips, Sharrow’s design uses looped ones that twist like a ribbon when powered up. The result, they say, is a boat that creates far fewer tip vortices, which significantly cuts down on cavitation. Sharrow claims independent testing already shows boats equipped with their propellers reduce underwater noise by up to seven decibels in the frequency range whales use to communicate.
Related: [Is it loud in the ocean?]
Now, they are also partnering with renowned marine conservation organization Ocean Alliance to test its quieter propellers on research expeditions near whales. It’s still early, but Greg Sharrow, the company’s founder and CEO, believes that a shipping industry that embraces his quieter propeller could make a meaningful impact on making the ocean a bit quieter.
“I think any situation which is a win-win, which is better for the environment, better for the animals, and ultimately better for the consumer and the operator, absolutely is good,” Ocean Alliance CEO Iain Kerr tells Popular Science.
“I think there is an enormous component of common sense here,” he adds.
From violin-recording drone to quiet boats
Greg Sharrow didn’t initially set out to save the whales. In fact, his original idea for the propeller wasn’t sparked by boats at all, but by drones. Academically trained in classical composition, Sharrow spent around 15 years working as an executive producer and director specializing in broadcasting orchestras. During that time, he became obsessed with nailing a very specific shot: using a drone outfitted with a video camera to record a violinist from within the orchestra itself. But anyone who’s spent any time around drones knows they aren’t exactly subtle. That high-pitched, beehive-like buzzing is a real problem when you’re trying to record the subtleties of orchestral instruments with exceptional dynamic range. Sharrow realized that to get the shot, he needed something that didn’t exist: an absolutely silent drone.
Diving headfirst into propeller design, Sharrow quickly surmised that the single biggest contributor to the flying robot’s awful shriek was the propeller itself. Cutting out that sound, he figured, would require getting rid of the noise that’s generated at the drone’s propeller’s tip vortices. The proposed solution was surprisingly simple in concept but incredibly difficult to realize in practice.
To quell the drone’s noise, one would need to engineer a tipless propeller. That might not sound like a huge departure, but the modern screw propeller design, patented by inventors Francis Pettit Smith and John Ericsson in the 1830s, has remained more or less unchanged to this day. This history of propeller design, in other words, isn’t exactly one of moving fast and breaking things.
“I asked myself this very simple question: what would a tipless propeller look like and how would it function?” Sharrow tells Popular Science. “And I kept asking that question over and over again. When I went to sleep, when I woke up the next day, when I was walking my dog, this idea just popped in my head. “
All that thinking led to another, much more significant realization, one that would chart the course of Sharrow’s business. He’d first fixated on quiet drones, but his proposed solution could have wider implications. A tipless propeller wouldn’t just apply to drones. In theory, it could apply to anything with a propeller. That means boats, and lots of them.
“I knew instantly that I had solved the noise issue that I wanted to solve, but also had invented a more efficient propeller as well,” Sharrow adds.
Sharrow says he and his team decided early on to prioritize boats over drones, though he says he hasn’t given up on silent drones forever. It doesn’t hurt that the market for quieter, more efficient boat propellers is also more active. Initial testing of his homemade tipless propeller prototypes started in a fish tank. He iterated again and again, eventually creating over 640 prototypes before partnering with the University of Michigan, work that led to a real-world test placing the propeller on a dinghy. Fourteen years on from that prototype, Sharrow is now a full-on propeller manufacturer, operating out of a 60,000-square-foot facility in Detroit with support from Ford Motor Company.
But does the propeller design actually cut back on noise? On the surface, the answer is a clear yes. Videos shared with Popular Science comparing the same boats equipped with a screw-based propeller and Sharrow’s show a clear auditory difference. The company’s own marketing material claims it achieves an 80 percent noise reduction compared to traditional designs. Sharrow says the company tested this by placing microphones and decibel meters around areas where boats with the propellers have driven, and they’ve measured up to a 20 decibel reduction in sound pressure level using a microphone at the helm of a test boat. If accurate, that’s a significant noise reduction. A 20 dB reduction in sound is roughly like stepping out of a room with a roaring vacuum cleaner into one where a group is having a dinner conversation.
That’s great news for boaters, but whales don’t spend all that much time above water. To understand whether this propeller change makes life quieter for them, you need to know whether the volume decreases underwater. To that end, Sharrow claims testing using systems, surface vessels, drones, and fans have shown the propeller reduces underwater noise anywhere between 3 to 24 dB at frequencies spanning 10 Hz to 20,000 Hz., which falls within the frequency range whales communicate in (between 10 and 300 hertz). The company claims they’ve also measured a reduction of up to 15 decibels in the narrower field between 10,000 and 20,000 hertz. That range of decibel reduction is quite large. Sharrow says these specific sound reductions achieved will vary based on frequency, application, and operating condition. Anecdotally, Sharrow says customers using the propellers are seeing more marine life and can get closer without them scurrying off, presumably a byproduct of the quieter design.
“Different marine species rely on different frequency ranges, so the potential benefits are not confined to a single band,” Greg Sharrow tells Popular Science. “Reducing underwater vessel noise where it overlaps the sounds animals use to communicate could help them hear one another with less interference.”
“We have heard from companies that have our propellers on whale watching charters that they see more whales now that they’re using shale propellers; they see more whales than they typically do,” Sharrow said. “We believe that’s because the noise pollution from a Sharrow is dramatically reduced. Sea life is either curious about that, or they’re less threatened by the noise.”
When asked whether that decibel reduction would make a meaningful difference for whale communication, Fournet generally agreed it sounds like a step in the right direction, though she stopped short of calling it some silver bullet. She said she’d ideally like to see more testing confirming those results, especially as the technology scales up and gets placed on more and larger vessels.
“As a general statement, if you can reduce the output of the vessel by seven decibels, you have made an ecologically meaningful reduction in sound,” Fournet said. “Anything that we can do to make propellers quieter is a good place to start.”
Taking their propellers to sea
Controlled lab testing matters, but so does observing real-world effects. That’s where Ocean Alliance comes in. Formed in 1971 by American environmentalist Roger Payne, the nonprofit was one of the first organizations explicitly dedicated to protecting whales and their habitats. The organization was foundational to the Save the Whales movement and advocates for protective legislation, including the 1972 Marine Mammal Protection Act. In recent years, the organization and its CEO, Iain Kerr, have spoken out about the dangers boat-induced noise pollution poses to whales. Ocean Alliance also regularly tests out new technologies to advance its advocacy and scientific research, like this “SnotBot” drone that can fly through a whale’s blowhole to collect biological samples.
This mix of hands-on advocacy and a willingness to take chances on new tech makes Ocean Alliance a natural fit to test Sharrow’s propeller near whales on a mission. Kerr, speaking with Popular Science, says he came across claims online that the company’s propellers could reduce underwater noise and improve boat performance. He was initially skeptical but also curious, so he reached out and asked to test them. He recently outfitted a boat with the propeller and ran it through a 75-mile trip.
Kerr says the results were “crystal clear.” Using the new propellers, he says the boat was noticeably quieter, caused less vibration, and was immediately more fuel efficient. While on the boat, Kerr, who was himself once a boat captain, says he noticed fewer cavitation bubbles forming behind the boat. These results are promising for Ocean Alliance on multiple fronts: less noise means less harm to the whales, but it also means researchers can potentially get closer to whales without causing as much disturbance, which could aid their studies.
“For me, it’s super simple,” Kerr says. “If I can be part of the solution as against part of the problem, I’m over the moon.”
“I like a win-win,” he adds. “I love a win, win, win.”
Oceans are overwhelmed with noise
Promising though those testimonials may sound, more testing is necessary to solidify them into hard, verified science. It would be naive to think altering a single component on a smaller research or fishing vessel will suddenly turn down the ocean’s master volume.
It’s estimated there are hundreds of thousands of vessels making their way across the world’s oceans and seas every day. Around 6,000 of those are massive, hulking container ships responsible for keeping global shipping afloat. In addition to playing an outsized role in global carbon emissions, these leviathans of trade are also a major contributor to underwater noise pollution. If the ocean were city streets, container ships would be the roaring 18-wheelers that drown out restaurant conversation and set off barking dogs. Sharrow tells Popular Science the company doesn’t currently possess the ability to alter container ship propellers, but it’s something they’re working toward.
“We are very confident that we’ll be able to manufacture at very large scale sizes these propellers for container ships,” Sharrow said.
Until then, efforts to make life less noisy for whales will require a more multi-pronged approach from many different sectors. To that end, Fournet says there’s some obvious low-hanging fruit. Advocates or lawmakers can pressure shipping companies to slow down their vessels, even slightly, to reduce the overall noise they contribute. Similarly, shipping routes could be adjusted so there are more gaps between arrival and departure times. Those brief reprieves would at least give marine life pockets of quiet in which to communicate.
“Your best bet for reducing chronic noise, which is a time problem, is to ensure that there are periods when no boats are there,” Fournet says. “Making the boats quieter, that’s step one. The other is about making sure that you have set up a system so that there are periods when there are no boats around.”
‘Everything that we buy makes noise.’
There’s also reason to believe life for whales can improve rather quickly once the cacophony subsides. Fournet’s previous research into humpback whale populations off Southeast Alaska detailed declining rates of whales calling out to each other year after year. But that suddenly changed in the spring of 2020 when COVID-19-related lockdowns took hold. Those restrictions meant whale-watching vessels and cruise ships that had occupied that area nearly nonstop for the better part of half a century were held at dock. For the whales, that meant their first truly quiet summer since the ‘70s.
For the first time in a generation, these whales could really hear each other. Remarkably, Fournet says that peace and quiet made the whales chattier. Listening in as part of her research, Fourney says the way those whales communicated became notably more nuanced and complex. Rather than repeating the same calls over and over, the whales relied on a wider range of call types. In fact, the calling patterns more closely resembled those recorded back in the 1970s, before the ocean was filled with vessels. That suggests whales and other marine life can see improvement quite quickly, given prolonged moments of silence.
“If we can make boats quieter, we can make the ocean a better place for marine organisms to live,” Fournet tells Popular Science.
Creating those moments of quiet isn’t an abstraction, either. All those container ships and fishing vessels are only generating noise in the first place because there’s a consumer downstream paying them to do so. By simply opting to purchase more goods locally, Fournet notes, everyday people can play at least a small part in reducing their overall contribution to ocean noise. In other words, a farmer’s market apple might not just taste better; it’s better for whales too.
“In this case, sure, humans are the problem,” Fournet adds. “Humans in this case are also the solution. We created this problem, but we do have the capacity to fix it.”
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