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Quieting the Global Growl

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Re: Quieting the Global Growl

#31

Post by advisedwang »

jeffbee wrote: post #9
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.

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. https://www.int-res.com/articles/meps2006/309/m309p279.pdf As an aside, I love discov…

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.

[1] https://en.wind-turbine-models.com/turbines/1419-mhi-vestas-...

Re: Quieting the Global Growl

#32

Post by marssaxman »

spinach wrote: post #21
sdenton4 wrote: post #13

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 b…

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.

Re: Quieting the Global Growl

#33

Post by cactusplant7374 »

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…

Which fact did you find the most interesting?

Re: Quieting the Global Growl

#34

Post by schiffern »

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.

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

Re: Quieting the Global Growl

#35

Post by emilecantin »

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'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.

Re: Quieting the Global Growl

#36

Post by jeffbee »

advisedwang wrote: post #31
jeffbee wrote: post #9

Earlier quoted context omitted.

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. https://www.int-res.com/articles/meps2006/309/m309p279.pdf As an aside, I love discov…

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. [1] https://en.wind-turbine-models.com/turbines/1419-mhi-vestas-...

That explains why they would make broadband noises but not peaky high-q noises like the ones in the paper.

Re: Quieting the Global Growl

#37

Post by _yb2s »

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.

Re: Quieting the Global Growl

#38

Post by _yb2s »

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

Fascinating, I'm really into boating and sailing and have never heard of this- no consumer grade engines or boats that I know of have this.

Re: Quieting the Global Growl

#39

Post by _yb2s »

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.

A lot of the noise is from the combustion engines themselves- exhaust often releases underwater, and the engine vibration transmits through the hull.

Re: Quieting the Global Growl

#40

Post by ericd »

marssaxman wrote: post #32
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.

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.

True, those sounds are somehow less grating, though. I hate two stroke motors with a passion.
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