If you're a layperson interested in these sensory questions, I highly recommend the book An Immense World by Ed Yong. It's a 400-something page tour through the many senses animals have and we (mostly) don't. It might have the highest density of truly cool animal facts per page of anything I've ever read, despite being written for adults who maybe haven't considered themselves the audience for fun animal facts in decades.
I'll have to check this out. I thoroughly enjoyed Sensory Exotica by Howard Hughes which does a deep dive into four extraordinary senses: biosonar, biological compasses, electroperception, and chemical communication
"Most" is pretty hard, so I'll just pick one I think is good. I'm paraphrasing here, so errors are mine.
Sea otters, which feed themselves through long dives to and from the ocean floor, with a blind and hurried pawing for urchins in the middle, have hands that are about as sensitive as human hands, but significantly faster. Tasked with distinguishing boards with slightly different small ridges, humans compare and re-compare before deciding; if an otter touches the correct board first, it doesn’t touch the second one at all. This is true even though a human fingertip, if inflated to the size of the earth, is sensitive enough to distinguish between cars and houses. A manatee’s face is about as good.
If you have the chance to listen to actual boat noise from an underwater microphone, you’ll be surprised at how loud it is and how far sound can travel. It’s less of a problem with pleasure boats and more of an issue with commercial ones like container ships. Other sounds that are loud underwater and harmful for animals include wind turbine noise (from spinning giant blades) and sonar pings.
I've done some snorkeling on coral reefs in the Bahamas, and it's crazy how far you can hear boats. Once you learn what sound they make (it's completely different underwater), you can hear one very clearly but when you pop your head up it's way off in the distance. And this is just for smaller, outboard-powered boats.
I've never really had the chance to hear a big ship underwater, but my home is right by the St-Lawrence seaway (the one they talk about in the article) and when it's quiet at night I can feel the rumble they make through the ground when one passes in front of the house.
I'm not a fluid mechanics guy, but all that cavitation from the screws seems like preventably wasted energy, not to mention a huge source of potential surface wear.
I'm surprised PBCF isn't more common. It essentially reduces swirl and cavitation in the central vortex, converting it into additional thrust while also reducing shaft torque. It's an inexpensive retrofit (payoff time <6 mo) with broad compatibility, and the swap can be done while unloading with no downtime. And yes, it reduces rudder surface erosion which is caused by cavitation.
Seems like a no-brainer. Maybe folks just aren't aware of the technology?
Nuclear submarines feature very large, many-bladed, specially-shaped propellers often turning very slowly to reduce both noise and wear (though more the former: stealth is key to submarine operations).
Cavitation on hydraulic and steam turbines, as well as other hydraulic mechanisms, is a major source of wear and failure. Keep in mind that cavitation is equivalent to boiling, and involves both high (if localised) temperatures and extreme pressure fluctuations as cavitation bubbles form and collapse.
For nuclear submarines, overall efficiency isn't tremendously important, as when the sub needs to move quickly the powerplant can turn out a heck of a lot of power.
Checking just now to confirm powerplant output, I'm learning that the Virginia class of hunter-killer submarines, for which both quiet operation and speed for pursuit are concerns) use pump-jet propulsors rather than traditional bladed propellers, specifically to reduce cavitation:
Top speed is in excess of 25 knots. (I suspect considerably in excess, though
Powerplant is a 210 MW nuclear reactor, 280,000 HP equivalent. By contrast the Maersk E-class container-ship (largest in the world until 2012) have an 81 MW (fossil-fuel based) powerplant, 109,000 HP equivalent. The still-larger Triple-Es have two 31 MW engines (for lower total output), and the current size giant CSCL Globe 69.7 MW.
And the fastest known military submarine seems to have been the K-222 Soviet Project 661 "Anchar", which could reach 41-45 knots (about 50 mph) submerged. The K-222 is slightly shorter than the Virginia class, and as hull-length has a strong effect on top speed (see hull speed: <https://en.wikipedia.org/wiki/Hull_speed>, though how this relates to submarines I'm uncertain, see also Froude number: <https://en.wikipedia.org/wiki/Froude_number>), I suspect Virginia class boats could likely achieve similar speeds should the need exist.
According to this (highly interesting) paper I just read, it seems that the operating sounds of wind turbines come from the gearbox, which makes more sense to me because the blades of offshore turbines are turning very slowly. Also according to the same paper, the operating noises of offshore wind farms are probably not significant.
As an aside, I love discovering a researcher with such a delightful niche. How many people are out there researching "Acoustically mediated fin whale mating"? Amazing humans.
Wind turbines are moving a lot faster than they appear. E.g. Vestas v164 [1] rotates only at max 12 times per minute so looks slow. But because it has 80m blades, the tip speed is up to 100 meters per second (230mph). That's 1/3rd the speed of sound! That can generate a lot of noise.
My experience disagrees with that claim. But I suggest an easier way to verify this, which is to just go to YouTube and look at videos of the sound produced by wind turbines on land. You will hear the distinct loud woosh sound of the actual blades and not the gearbox. Personally, I feel a lot of the academic denial around this noise issue is from people with an activist goal.
YouTube videos are not very difficult to edit. If you search YouTube for “noisy windmills,” I’m sure you’ll get… something.
Anyway windmills are all over the place, lots of people have had the experience of being near them. If they make too much noise, that’s a problem of course, but I think lots of people can verify the existence of non-noisy ones by virtue of having seen them in person. So, sure, loud designs should be avoided since there are perfectly good alternatives.
I mean, nobody would say the academic publishing ecosystem is super healthy (every academic hates it, for one). But the existence of something like “retraction watch” points to the fact that these aren’t really comparable ecosystems. Nobody need bothers to catalogue the lies on YouTube because that’s an impossible and pointless task.
The academic process has always been messy and political, and yet universities do keep churning out research and students.
> The academic process has always been messy and political, and yet universities do keep churning out research and students.
The youtube process has always been messy and political, and yet new creators do keep churning out great content that people love watching and spreading awareness about various issues.
:)
The youtube show :
“Undecided by Matt Ferrell” is my favourite
Lotta clickbait, too. They need it to keep earning, even if they don't like it.
I recall Tom Scott saying there was one video he basically couldn't make, because the climax was switching on a big light, which was actually silent, but it felt wrong unless he dubbed a sound over that and such dubbing was against his editorial standard.
That’s interesting. Without knowing what the switch was, I guess it is hard to say, but a switch that kicked off some big process silently seems like it could be really dramatic and cool.
sound and radio are of course waves in completely different media. why would low frequency radio waves be insane to wildlife? it's not like it's microwave (which would cook them) or pressure (sound) which directly physically damages their organs. almost by definition low frequency radio waves are low energy, so I don't see how this would be more dangerous to Flipper than my Wi-Fi router is to me
I’m talking about sound not electromagnetics. It’s like a torture for marine life to be surrounded by constant noise. Many also use sound to communicate or locate.
Huh, sharks pick up EM signals, right? I wonder what they think of this stuff
But just to be clear, I don’t think we should suppose it is damaging and try to ask the military to stop using it (good luck, lol). It could be worth looking into though.
Sure, but sharks use them as a sense. We all pick up photons in the sense that we can all feel the warmth of the sun on our skin, but also, it is sometimes interesting to think about how people who aren’t blind perceive light.
It's one of the things that I find fascinating about Naval tech. From the sonar from each boat to the network of devices like SOSUS net[0], you have to be very good and deliberate to sneak around in the oceans.
Even the above water noise is awful... I am sensitive to noise, and do engineless sailing partly because the sound of motors is awful, and ruins the fun of boating for me.
when i was a kid we often camped near a river. every morning i heard music but i couldn't identify the source. "it comes from the other side" my uncle said. that day i learned how far sound can travel in the water
Recently I saw a video of a dolphin that came up to a boat and was imitating the sound of a boat motor. It looked playful, but perhaps it was complaining about all the noise.
It think it was an orca, I saw this yesterday also. We're all curious what it's trying to communicate, but I like the idea of it repeating back to us what is a very annoying sound to them.
I remember watching a nature TV show as a kid in which the presenter waxed lyrical about the way a group of dolphins took one dolphin's vocalization and repeated it and riffed on it, claiming that they were improvising musically together like a jazz group. I remember thinking that it was a very optimistic assumption, and it was just as likely that the rest of the dolphin were mocking and bullying the first dolphin.
That train of thought probably says something about what I was going through at the time, but given other things we've learned about dolphins, I wouldn't discount my idea.
Yacht in this context typically refers to a rather small sailing boat. It affects small-scale fishers and things like that, not the large motor yachts rich people have.
Thanks for pointing it out, I didn't know that orcas are dolphins too. The one I saw was like a "bottlenose dolphin" with the classic dolphin shape and color.
> The orca, or killer whale, is a toothed whale that is the largest member of the oceanic dolphin family.
> Oceanic dolphins include several big species whose common names contain "whale" rather than "dolphin", such as the round-headed whales including the false killer whale and pilot whale). The Delphinidae family also includes the porpoise, beluga whale, and narwhal.
If you make incredibly loud noises above water, humans will complain, and you'll end up reducing the noise, due to some combination of workplace safety regulations, litigious neighbors, and self-regulation.
People don't experience underwater noise directly, though, and so it is allowed to be arbitrarily loud and has gone almost completely unchecked, and is undoubtedly harmful got marine ecosystems. It is thought to be a major factor in whale beachings, for example.
Humans in cities have also got used to the noise. Go from a quiet forest or rural area in the middle of nowhere to a city or residential area where you have cars, trains, lawn mowers, leaf blowers, air planes, loud barking dogs, etc. It's shockingly noisy. It's surprising that people don't want to do more about the noise pollution but it seems many just got used to it.
Rural areas can be noisy, too, depending on the ecosystem: birds, frogs, crickets, and cicadas can all kick up quite a ruckus. One can get used to just about anything.
on a tangent, I was living about 15min SW of DFW airport when 9/11 happened. When the FAA grounded all air traffic i remember going outside and thinking how strange it was not hearing planes in the sky. I had become acclimated to all the air traffic and when there was none it was pretty eery.
Another tangent, I went on a trip to LA. The drive to airport was noisy, airport was noisy, airplane was noisy, city was noisy, air conditioner in room was noisy. This went on for the whole week. I didn't really notice.
But when I got dropped off at my car after the flight home, to get in my car it was late at night in a small town. And I noticed it. The silence. I stood there, beside my car keys in hand for a good 5 minutes, just taking it in.
I had no idea how noisy it had been for the past week until then.
