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

[Vikinger]

Originally Posted by Engel der Vernichtung

Possibly better picture for dipping sonar.

Basically, to do this, the helo stops and hovers a few meters above the water, then lowers the sonar probe, and listens. If they hear something susupicious, then they go active, and try to immediately locate the sub. If they don't hear anything, they winch in the probe, fly over a few hundred meters, and try again (usually also being given steering commands by the ship they're operating from; the ship's sonar, being a lot bigger is also a lot more sensitive, and between the two they can pinpoint a sub pretty quickly). Usually helos in this mission are armed with 2 homing torps.

Yeah its a better illustrating picture .

A bit off topic but i remember when i was in the Swedish Army and the russian submarine went aground on an small island in a military secured area.

After that incident the Swedes saw submarine everywhere and hunted them like maniacs in the archipilago.

I was on watch duty on my regiment when we got a call and they sent our platoon in as reinforcment. Mainly to secure some bridges and roads along the coast.

I was placed on a small bridge whit some mates. We got sharp ammo and a few handgrenades. It was quite thrilling , specially in the night where both sound and movement can play trick on your mind.

We had order to use our weapon if we had to.

But to make a long story short. We never saw or heard any indication of hostile activity but some guys managed to kill a few ducks and swanes. They thought they saw some scubadivers in the water and throw a few handgrenade at them.

But it was a lot of talking about it after wards. Swedish army kill ducks whit handgrenades hehe.

But iam sure that thos guys that threw the grenades did it on purpose to , well, have some fun during the boring patrol.

And the picture i posted is one of thos moments i saw when swedish navy used hellicopters to search for sub activity. So its a real action picture. ( and to clarifie, i did not take the picture but it show how it looked like)

To bad i never saw any sinkbombs attack. They was to far out from where i was stationed. But they dropped quite few of thos barrels.

But it would be intressting to se sharp sinkbombs in action

[Seminole]

A bullet travels at supersonic speed and you won't hear one traveling until it smacks into the wall of your house and creates vibrations in the air that your ear can pickup on.

Same thing with a sonar pulse hitting the hull of a submarine.

[tycho102]

Originally Posted by caspofungin

british ww2 asdics used pings in the range 14-20Hz -- well w/in the hearing range of humans.

re constant pinging -- that's true, in ww2 escort vessels constantly had the asdic operating. unfortunately, that's not implemented in sh3 (although i seem to recall it in silent service 2).

It's been my understanding that the lead escort would race forward and cut engines back, then zig-zag with active sonar while the rest of the convoy caught up. The side escorts were responsible for the quartering attacks, and would do ovals -- racing forward, then cutting their engines and circling until the convoy was abeam, then racing foward again.

I've also heard that some WW2 sonar was ultrasonic. Whether it was the Yanks, the Jerries, the Brits, or the Japs, I don't know. It may have been late 1940's sonar that went ultrasonic for awhile. You get better "resolution" with higher frequencies, but the power efficiency drops as with any transducer/speaker (basic induction).

Originally Posted by Seminole

A bullet travels at supersonic speed and you won't hear one traveling until it smacks into the wall of your house and creates vibrations in the air that your ear can pickup on.

Same thing with a sonar pulse hitting the hull of a submarine.

Actually you will hear a supersonic bullet go by even if it doesn't hit anything. I leaves a sonic boom behind just like a supersonic plane, but much quieter. It sounds sort of like a hand clap right near your ear. You can hear them as much as 5 feet away.

[Ula Jolly]

There are some misunderstandings here.
Basically, imagine a rod in space that is the length of one lightyear (ehrm, LONG). If you push in one end, will the other end move accordingly after one year, because it takes the light that much time to travel there? Not at all, it will move after time that is a product of the speed of sound in that material, which is much slower. When you push a rod, you push one atom, which hits the other atom, which hits the other atom, and so forth. This does not happen instantly, but with microscopical delays. THIS is speed of sound. In air, the speed of sound is rather slow (341 m/s I think) because there's a distance between the particles. In higher elevations the speed is slower, because the particles need to travel even MORE of a distance.

The speed of sound in water can be found (in feet/second at least) by use of
4388 + 11,25(temperature °F) + (0.0182 x depth + salinity (in parts-per-thousand, which I think is close to 35))


If I am not commmpletely off, that speed should be about 1500 m/s. I'm not doing the maths, though. Basically, as with a RADAR, this also means that the TARGET hears the ping before anyone else. The time from the ping being sent out by the attacker, till it hits the target, is X. The time from the ping being sent out till it is heard by the attacker, is 2X, because the sound wave travels double the distance. These mechanics are not like those of a bullet in air.

Now, the pulses... are just pulses. The pushing of atoms, the frequency being how often the atoms are pushed in a second (translating to hertz).

Active sonar does not automatically give you a bearing of the contact unless you can distinguish his shape (a long boat's silhouette points in two directions, you figure out which he is facing by). A user of active sonar can not expect to make NO use of other sensors, unless the target is stationary. However, then he'd have to KNOW the target is stationary - only two or more pings may determine that. In a submarine, the user would definitely need use of hydrophones (passive sonar) and any other data he might be able to find.

Note that I do not claim to know the mechanics behind HEARING the ping. I, as someone posted before, expect that the hull of the submarine might act as a converter of sorts.

[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:

[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:

[Clint1]

Wow!

Usually the simulation fans are quite smart with basic physics, but this subject clearly was over someones head. First of all, the poster apparently did not mean supersonic, because the sound travels at a constant speed in a designated medium, in this case salinated water (pressure does affect the speed a little, but ALL SOUND travels at the SAME SPEED in SIMILAR CONDITIONS!) I think he ment ultrasonic (above our hearing treshold, 20 KHz) Someone was right to point out that the allied ASDIC during WWII was well within our hearing treshold. Somebody else totally missed the boat by "scientificly" bringing passive sonar (which does not emit any sound at all. Period) into this conversation.

To sum it up: it is realistic to hear the ASDIC in a WWII simulation, unless the sailor is middle aged, which would in average mean, that he could not hear the asdic anymore due to age related degradation of high frequency hearing.

Ilkka Pakkala M.D. PhD
Finnish Armed Forces
Active medical officer
(Navigation officer in naval reserves)

[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.