The PING is supersonic. So why do we hear it?

[Quagmire]

I cant get enough of the Fleet Type Submairne manual at this website: http://www.maritime.org/fleetsub/ I have read to the Sonar operators section now and the more I read the more I cannot wait for SHIV! Those uboots are in the stone age compared to the average USN fleet boat!

Anyway the manual describes echo ranging or "pinging" as supersonic meaning that the ping cannot be heard without receiving gear. So why do we hear it when we are crapping our pants in the control room?

Also the manual states that escort vessels ping constantly due to the noise they make at high speeds? This doesnt seem to happen in SHIII. They only seem to ping when they detect you.

Or am I missing something???

Here are the links that I am referring to:

Supersonic listening: http://www.maritime.org/fleetsub/sonar/chap5.htm#5A

Single Ping Echo Ranging: http://www.maritime.org/fleetsub/sonar/chap6.htm#6A

[Drebbel]

Those uboots are in the stone age compared to the average USN fleet boat!

Then why where new designed post-war subs around the world mainly copies of the German type XXI ?

[Quagmire]

Well the XXI was a whole new class of boat. When I say stone age I am comparing the average VII or IX to the average USN fleet boat.

From the air and surface search radar to the ice cream machine I would rather be in the USN for sure!

[Keelbuster]

Kindof a cool question. Not sure, but - from the single-ping echo ranging link:

4. Keep your eyes on the revolving slit and listen intently for the echo. Disregard the rolling reverberations, and concentrate on catching the clear note of the returning echo from the target. At the instant it comes, note the reading on the scale. This is the range.

But this 'audible' ping is through a transducer - i.e. a hydrophone of some kind. So why do we hear it inside the sub? Well, I think long-range sonar pings are high amplitude. The hull probably acts as a kind of transducer (like a big drum) and you get some kind of sound from the transformed ping energy - even if it was originally a frequency that humans can't hear audibly, the hull may act as a low-pass filter/transducer that warps a high frequency ping into the audible range. Not sure - just a guess. I know that modern subs also use High-frequency sonar that doesn't travel a long distance and is not detectable except at close range. I feel like the ping-echo we hear has something to do with the amplitude of signal required to travel long distances. But I'm not sure. I don't even know how a hydrophone works.

Edit: Also - think of diffraction of light - when it passes from a good conductor to a poor conductor, it's frequency gets warped downward (i think). So the good sonar medium is water, carrying a high frequency signal, and the air inside the sub is a poor medium, resulting in the high frequency signal being warped into a lower frequency signal that happens to be in the audible range.



Kb

[Quagmire]

A logical enough explanation Keelbuster. However can any ex-navy guys give us any hard facts? Any ex-sonar operators with us?

Thanks!

[Vikinger]

Iam not an sub crew but there is difference between active and passive sonar.

Active sonar is much more lauder and use a frequency that human ear can detect.

It was surface weasels that used active sonar and today also used by helicopters.

No submarine is using active sonar coz of the risk of detection today.

Difference is also that active sonar works like a radar. It detect objects by bouncning sound. While passive sonar is more listen to the surrounding like propchafts, engines etc.

If u want to know about sonar u can check it out here:

http://en.wikipedia.org/wiki/Sonar

[Konnrade]

Originally Posted by Vikinger

Iam not an sub crew but there is difference between active and passive sonar.

Active sonar is much more lauder and use a frequency that human ear can detect.

It was surface weasels that used active sonar and today also used by helicopters.

No submarine is using active sonar coz of the risk of detection today.

Difference is also that active sonar works like a radar. It detect objects by bouncning sound. While passive sonar is more listen to the surrounding like propchafts, engines etc.

If u want to know about sonar u can check it out here:

http://en.wikipedia.org/wiki/Sonar

Also used by helicopters? Do they drag a sonar probe through the water beneath them?

[Cerberus]

Originally Posted by Vikinger

Iam not an sub crew but there is difference between active and passive sonar.

Active sonar is much more lauder and use a frequency that human ear can detect.

It was surface weasels that used active sonar and today also used by helicopters.

No submarine is using active sonar coz of the risk of detection today.

Difference is also that active sonar works like a radar. It detect objects by bouncning sound. While passive sonar is more listen to the surrounding like propchafts, engines etc.

If u want to know about sonar u can check it out here:

http://en.wikipedia.org/wiki/Sonar

Active sonar sends out a loud 'ping' which is like holding up a big sign saying 'I am Here!' - but does allow you to get (fairly) accurate range & bearing data on your target of interest.
Passive sonar produces no noise but doesn't give any range data & (sometimes) only approximate bearing data. You need to plot stuff over time to develop a picture of what it is, where it is & where it's going.

Subs all carry active sonar but never use it, except possibly in the last few seconds before firing on their target.

Surface ships are so noisy that subs already know where they are, & hence using active sonar is a practical measure.

The operating frequency of an active sonar is determined by it's purpose.
High frequencies don't propagate as well, so for long range detection, the optimum frequency is slap bang in the human audio range.
(The sound frequency that propagates best in water, is the frequency to which the human ear is most sensitive. The light wavelength that propagates best in water, is the wavelength that the human eye is most sensitive to - coincidence or evolution at work?)
For shorter range stuff (like an echo-sounder) higher frequencies are useful because shorter wavelengths allow you to 'see' finer detail and the transmit/receive transducers can be smaller.

The most common description I've read of hearing the ping inside the boat is "it sounds like someone throwing gravel against the hull".

[MENTAT]

Originally Posted by Quagmire

I cant get enough of the Fleet Type Submairne manual at this website: http://www.maritime.org/fleetsub/ I have read to the Sonar operators section now and the more I read the more I cannot wait for SHIV! Those uboots are in the stone age compared to the average USN fleet boat!

Anyway the manual describes echo ranging or "pinging" as supersonic meaning that the ping cannot be heard without receiving gear. So why do we hear it when we are crapping our pants in the control room?

Also the manual states that escort vessels ping constantly due to the noise they make at high speeds? This doesnt seem to happen in SHIII. They only seem to ping when they detect you.

Or am I missing something???

Here are the links that I am referring to:

Supersonic listening: http://www.maritime.org/fleetsub/sonar/chap5.htm#5A

Single Ping Echo Ranging: http://www.maritime.org/fleetsub/sonar/chap6.htm#6A

I think you are mistaken buddy, USN was worst in "underwater" warfare in WW2. being gato class submarine was the worst considered by many.

Originally Posted by MENTAT

I think you are mistaken buddy, USN was worst in "underwater" warfare in WW2. being gato class submarine was the worst considered by many.

I've never heard of anyone who served on a Gato saying it was "the worst"; anyone who did not serve on one wouldn't know the difference. Please give references, preferably quotes.

[CCIP]

Also, how was USN "the worst", if it's the only sub fleet in WWII that fought and won a commerce war (give or take a number of other allied boats, of course)? They must've done something right, even if we all know that their fleet boats were not built for the role they ended up performing... :hmm:

[Vikinger]

Originally Posted by CCIP

Also, how was USN "the worst", if it's the only sub fleet in WWII that fought and won a commerce war (give or take a number of other allied boats, of course)? They must've done something right, even if we all know that their fleet boats were not built for the role they ended up performing... :hmm:

Iam not criticise anyone but there was a huge difference between the uboat war in the pacific aka atlantic.

The japanese boats did nearly never go in convoys and most of the time whitout escorts. Also the japanse intelligence was easy for the US to crack and therfore they knew when boats sailed off. japanese refused to belive, during the entire war, that the US had cracked thier code so therefor they didnt change it.

Japanese had a different way to think and act. More or less they belived that the warships should stay togheter as a strong an powerfull fleet and didnt not commence any warship for commercial protection.
So i have to say that the subwar in the pacific was way much easier for the US Navy than it was for the germany Navy.

If same thing had happend in the Atlantic. No convoys, No escorts and when the sub crew knew when ships left port. The germany would won the atlantic war also.

But US Navy did a greate work in the pacific so i dont critcise what they achived. I just point out some major difference.

Vikinger.

[Subnuts]

I think you are mistaken buddy, USN was worst in "underwater" warfare in WW2. being gato class submarine was the worst considered by many.

Tell that to Japanese. :rotfl: