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

[theluckyone17]

From "Iron Coffins" by Herbert A. Werner (p.293):

... However, the thunder of the barrage was not nearly as frightening as the noises that preceded and followed the attack. At first it sounded as if something like a chain or an iron net were being dragged along the hull; then came a wild clattering, as if a great load of pebbles were bing dumped upon the boat. These were brand new sounds to all of us - and a terrifying turous experience... But I concluded - correctly, as I later learned - that the British were using a new search device akin to the Asdic.

If I've got the dates right, that would've been March 19th, 1944. I imagine that at some point prior to that, the Allies started playing around with sound frequencies higher than previously used, causing the shift from the high pitched ping that could be heard earlier to that "load of pebbles" sound.

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.

[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.

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.