7 ms·
How far does sound travel in the ocean?
- jsrjenkins 6y agoThe article doesn't actually answer the question. How many kilometers and what is the depth of the sound channel? Where does the pressure/temperaure ratio cause sound to difract? After reading such an article I feel none the wiser, as the words are barely defined and no specifics given. Is there anywhere else to find better info?
- DoofusOfDeath 6y agoIIRC, "Principles of Underwater Sound" by Robert Urick [0] is considered pretty good. A textbook that's helpful for actually implementing ocean acoustics models is "Computational Ocean Acoustics" by Jensen et al [1]. [0] https://www.amazon.com/Principles-Underwater-Sound-Robert-Urick/dp/0932146627 https://www.amazon.com/Principles-Underwater-Sound-Robert-Ur... [1] https://www.amazon.com/Computational-Acoustics-Modern-Signal-Processing/dp/1441986774 https://www.amazon.com/Computational-Acoustics-Modern-Signal...
- jsrjenkins 6y agoThank you for these. The First [0] link looks particularly interesting.
- Ensorceled 6y agoWhat a crappy article. Apparently the answer is "it depends" but they're pretty sure it is "many kilometers". > In fact, hydrophones, or underwater microphones, if placed at the proper depth, can pick up whale songs and manmade noises from many kilometers away.
- gmueckl 6y agoThis seems like a contradiction, but it isn't. Sound attenuation in sea water is extremely dependent on frequency. It is roughly a power law. Very low frequencies can easily travel extreme distances (0.001dB/km for 0.1Hz or so), but higher frequencies are attenuated more drastically. Whale song and man made noises have much higher frequencies. A quick Google search claims whale songs are around 80Hz to 4kHz. Absorption is around the 10 to 100dB/km range for 100Hz to 1kHz. So both statements in the article are true.
- jessep 6y agoDisagree! The article explains something extremely cool: that there’s a layer in the ocean that acts like a megaphone, where sound that passes into it gets caught and propagates way further. That’s cool and specific.
- koheripbal 6y agoMegaphones Amplify sound. Your analogy doesnt work. In no layer of the ocean is sound amplified.
- kube-system 6y agoElectric megaphones amplify sound. Acoustic megaphones direct sounds, much like what the article describes.
- jessep 6y agoYeah, I was thinking about the old fashioned cheerleading things, without any electricity involved. I even thought about being explicit in case someone was going to be pedantic ... there’s even an emoji for it
- OnlyOneCannolo 6y agoAn example would have been nice. It's old technology now, but here's an example of listening across the Atlantic. https://en.m.wikipedia.org/wiki/SOSUS https://en.m.wikipedia.org/wiki/SOSUS https://youtu.be/R462zEQ6RQA https://youtu.be/R462zEQ6RQA
- rhodochrosite 6y agoIt depends is the real answer for any things. Understanding what it depends on is an important part of the discussion. Most people have no understanding of sound in the ocean. There is a ton of information at: https://dosits.org https://dosits.org - Discovery of Sound in the Sea. -Full disclosure, I am affiliated with that website.
- cosmodisk 6y agoNot sure how it's nowadays, however during the cold war, those serving in Soviet submarines often wore slippers to avoid making any loud noises so their counterpart won't pick it up with their equipment.
- wil421 6y agoI saw an older show about submarines that said they had to use exercise bikes instead of treadmills. Repetitive running was easy to pick up.
- DoofusOfDeath 6y agoThis doesn't surprise me. In general, underwater sound attenuates more quickly as you increase its frequency. Foot-fall thumping has a pretty strong low-frequency component. It's also repetitious, which (I'm guessing but don't know for sure) probably makes it easier for a sonar operator to notice.
- wil421 6y agoSonar operators are pretty cool. I saw a clip where they identified another ship (or sub) because they heard a valve open or close. It sounded and looked like static to me but they said it was pretty clear to the trained ear.
- Lev1a 6y agoAnd then the sonar operator records the sound onto a cassette tape and plays it at 10x speed for the captain to convince them that they really are chasing another submarine. I love that movie so much...
- DoofusOfDeath 6y agoIf someone running on a treadmill sounds like whales humping, he probably needs to go on a diet :)
- koheripbal 6y ago
- pge 6y agoI worked briefly in this field. The key concept is the “sonar equation,” but it needs to be modified to include the factors of the specific area of ocean (depth, cylindrical/spherical propagation characteristics, temp, shipping traffic, etc). There are not a lot of public sources on the topic, but here’s one I found, if you want a starting point to learn more: https://fas.org/man/dod-101/navy/docs/fun/part08.htm https://fas.org/man/dod-101/navy/docs/fun/part08.htm
- mkj 6y ago100km in some circumstances, and 40km easily? https://www.cgg.com/technicalDocuments/cggv_0000027562.pdf https://www.cgg.com/technicalDocuments/cggv_0000027562.pdf That's a pretty loud "noise" though.
- vinay_ys 6y agoIf I were to guess, I think the temperature differential within the water layers make for sound to refract and diffuse quickly and not really travel in a straight line for too long.
- codingdave 6y agoSperm whales click at up to 230 decibels, so yes - the oceans can be quite loud.
- grenoire 6y agoI think a more approachable resource on (a superficial but fundamental level) is Smarter Every Day's SONAR episode. He discusses and illustrates the complexities involved in sound, how it doesn't even travel in a predetermined path, and the variables involved in its distance/trajectory: https://www.youtube.com/watch?v=AqqaYs7LjlM https://www.youtube.com/watch?v=AqqaYs7LjlM
- polytely 6y agoThat whole series is really good, life on a submarine is so interesting
- cbozeman 6y agoI spent two and a half years on one. No it is not.
- dylan604 6y agoJust because you're over being in a submerged tube doesn't mean other people can't find it fascinating. I find the silent service totally fascinating, and would happily buy you beers to hear stories you are not allowed to tell.
- cbozeman 6y agoWell how about I tell you the stories I can tell, for free? I have to go get a car battery replaced, but when I come back, I'll share a few tales. Sometimes, I would stare into the Reactor Compartment through the glass (there's a large-ish - around 6" - 8" if I recall correctly) porthole that allows you to look right into the reactor compartment at the nuclear reactor. I never stared for long... maybe 5-10 seconds at most, but staring at nuclear fission occurring is truly an awesome experience. There's no Cherenkov radiation emitted, so you're just staring through glass at a bunch of metal, but you still know its occurring... and that was enough for me.
- GuB-42 6y ago
- gliffie 6y agoFrom the southern Indian Ocean to both coasts of the US: https://staff.washington.edu/dushaw/heard/figtab.shtml https://staff.washington.edu/dushaw/heard/figtab.shtml
- DanWritesCode 6y ago> How far does sound travel in the ocean? > many kilometres Not exactly the answer I was reading for.
- georgecmu 6y agoThousands of miles: https://en.wikipedia.org/wiki/SOFAR_channel https://en.wikipedia.org/wiki/SOFAR_channel Analysis of Heard Island Feasibility Test data received by the Ascension Island Missile Impact Locating System hydrophones at an intermediate range of 9,200 km (5,700 mi; 5,000 nmi) from the source found "surprisingly high" signal to noise ratios, ranging from 19 to 30 dB, with unexpected phase stability and amplitude variability after a travel time of about 1 hour, 44 minutes and 17 seconds.[3]
- kwaldman 6y agoThanks for the link. I traveled on the Cory Choeust multiple times during the late 80s, though not on Heard island test. Very interesting working on SONAR in the 80s, both on surface ships and subs. Riding alone in the conning tower of an SSN in Exuma sound was fun. And saw a full rainbow in north Atlantic
- tyingq 6y agoDoes 70-80Hz count as sound? ELF works globally to talk to submarines with one very expensive base station. I suppose, though, only a very small amount of the trip is through the ocean.
- Lev1a 6y agoVLF can apparently penetrate about 30m of sea water worldwide [1] when transmitted from one base station into the atmosphere. Not sure about ELF though. [1]: https://en.wikipedia.org/wiki/VLF_transmitter_DHO38 https://en.wikipedia.org/wiki/VLF_transmitter_DHO38
- teleforce 6y agoBlue Whale is the world largest (30m/100ft) and also the second loudest (189 underwater dB) animal, has been reported to communicate for about 1600 miles or 2600 km away. This distance is approximately the distance of Puerto Rico to the shores of Newfoundland [1]. The loudest animal goes to Sperm Whale with 230 underwater dB, and it's louder than the sound of jet engine at take-off. According to experts, whale's consciousness and sense of self is based on sound, not sight. They communicate using sound types namely repeated songs (each song quantum duration of 15-20 seconds) and D calls (down-swept short pulse) [2]. I think that the longer repeated songs are for communication while the short D calls are for echo-location for determining sea depth, icebergs, islands and troupe of shrimps (their staple foods). The latter is similar to the mechanism being used by bats or blind human [3]. [1]http://news.bbc.co.uk/2/hi/science/nature/4297531.stm http://news.bbc.co.uk/2/hi/science/nature/4297531.stm [2]https://dosits.org/galleries/audio-gallery/marine-mammals/baleen-whales/blue-whale/ https://dosits.org/galleries/audio-gallery/marine-mammals/ba... [3]https://www.youtube.com/watch?v=lAtVOK04XvA https://www.youtube.com/watch?v=lAtVOK04XvA
- new_here 6y agoThere's a great episode from the Cosmos series where Carl Sagan talks about how the range of whale communication was inhibited by the development of steam engine ships: https://youtu.be/UwzukFBWxu4?t=765 https://youtu.be/UwzukFBWxu4?t=765
- PEJOE 6y agoSlightly related, but I remember NOAA used to have hydrophones streaming live to the internet and I would listen to them to fall asleep. One day one of the hydrophone lines was cut, and they stopped the stream and never restarted it. I would love to be able to hear live ocean sounds again.
- georgecmu 6y agoThe lack of detail is disappointing, but not entirely surprising given the historical context. The SOFAR channel in the ocean transmits low frequency sound waves for thousands of miles. Its existence and applications were kept classified until the 90s. https://en.wikipedia.org/wiki/SOFAR_channel https://en.wikipedia.org/wiki/SOFAR_channel
- mjfl 6y agoShouldn't the power of the signal fall off like 1/r^2? So really, not too far.