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Quieting the Global Growl

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Re: Quieting the Global Growl

#41

Post by blackeyeblitzar »

dingnuts wrote: post #6
ck2 wrote: post #4

Earlier quoted context omitted.

US Navy (and certainly others) kill many dolphins, whales and other sea life with their high powered sonar. US also has high powered ultra low frequency radio (ELF) for communication to subs and that's got to be insane to wildlife. https://en.wikipedia.org/wiki/Project_Sanguine

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.

Re: Quieting the Global Growl

#42

Post by ben_w »

teitoklien wrote: post #30
bee_rider wrote: post #29

Earlier quoted context omitted.

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 ke…

> 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.

Re: Quieting the Global Growl

#43

Post by sevensor »

schiffern wrote: post #34
sevensor wrote: post #12

Earlier quoted context omitted.

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.

Yes you're right. 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 Seems like a no-brainer. Maybe folks just aren't aware of the technology? https://www.youtube.com/watch?v=a8PjWSeLUzY

Wow, that's awesome! Looks like a big win all-around. Save money, save fuel, save wear.

Re: Quieting the Global Growl

#44

Post by edem »

blackeyeblitzar wrote: post #3

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.

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

Re: Quieting the Global Growl

#45

Post by te0006 »

_yb2s wrote: post #37
blackeyeblitzar wrote: post #3

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.

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.

Try a modern electric motor. There are some really quiet ones now.

Re: Quieting the Global Growl

#46

Post by pixelmonkey »

mycologos wrote: post #26

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 dec…

+1, a truly great book.

Re: Quieting the Global Growl

#47

Post by bee_rider »

ben_w wrote: post #42
teitoklien wrote: post #30

Earlier quoted context omitted.

> 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.

Re: Quieting the Global Growl

#48

Post by lioeters »

cess11 wrote: post #18
telesilla wrote: post #5

Earlier quoted context omitted.

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.

Orcas are dolphins.

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.

Re: Quieting the Global Growl

#49

Post by dredmorbius »

sevensor wrote: post #12
blackeyeblitzar wrote: post #3

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'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.

Correct on both counts.

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.

A couple of discussions from both perspectives:

https://archive.navalsubleague.org/2012/a-century-of-america...>

https://www.sciencedirect.com/science/article/abs/pii/S00298...>

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:

https://en.wikipedia.org/wiki/Virginia-class_submarine#Propu...>

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.

https://en.wikipedia.org/wiki/E-class_container_ship>

https://en.wikipedia.org/wiki/Triple_E-class_container_ship>

https://en.wikipedia.org/wiki/CSCL_Globe>

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.

Re: Quieting the Global Growl

#50

Post by MikeSchurman »

chasd00 wrote: post #22
spinach wrote: post #21

Earlier quoted context omitted.

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.

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.

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