ASDIC clarification

[Kelly621]

In twenty plus years of riding fast attacks and a couple of FBM's I never once heard any active sonar. Others on board did and described it similar to what has been already posted here, but being back aft by the propulsion equipment with ear plugs shoved in my ears I did not hear much of anything

Kelly621

[flag4]

*..off topic - a bit..*

I have a sonar ping for my ring tone on my android.



a bit like this but very clear -
I love it.

[Sailor Steve]

I've had one on my plain old cell phone for a couple of years now.

[nikimcbee]

On a side note, how did WW2 era sonar locate a sub on sitting on the bottom. Wouldn't the sub be lost in the return echo?

[Tupolev]

I'm thinking it would be dependent on what the ocean floor was comprised of near the bottomed submarine.

If its rocks/reefs/sunken ships then I'd think the return echo would be split up amongst those features. But if its mud or sand the ping's energy might be absorbed by the ocean floor, leaving the highly reflective submarine highlighted.

But then I could be completely wrong.

[Mittelwaechter]

You are in search mode for an U-Boot reported or detected earlier...
A flat sea floor will show a constant line on your echograph. Suddenly the echo returns faster and you detect an object sitting down there. A few meters further the line stays constant as before.
You turn the vessel and pass over for a second time. Again you get that object scribbled on your graph. What would you do, Captain? I guess you'd tell your hydrophone guy to listen at this very special spot, but in the end you'd probably roll some ashcans overboard, just to make sure this structure receives a hit.

With a rocky seabed (big rocks, reefs and shelfs), it would be different. Your echograph could not differentiate between rocks and Uboat hulls, but it would be risky for a U-Boot to bottom down there...

[ArditoCorsaro]

My grandfather (chief machinist on board the submarine torricelli in june 40, red sea, war cross for gallantry in action, he was wounded too and passed 7 years in pow camps in india, after scuttled the boat.) was ambushes by an hunter killer group in june 40 in perim strait, after a couple of days of cat and mouse game, they was forced to gun action. Badly damaged the hms sorehan and the hms karthoum (the last sunked the day after for unclear reasons maybe for the damages. A shell from the italian sub hit her torpedo depot.) and later being hit scuttled the boat for avoid capture.
He told me that the noise he heard (they stilled 12-18 hours on the sea floor, damages, and chased, witg 45-50 degrees inside, in shadow.) during the hunt, was something like if someone was beating the hull, but a very light noise, not like a hammer, and later something like "pstchhhh".for a couple of secobds the beating, and so something like a "pstchhh" .
Also the italian escort sonar should have been similar. Because in alfa tau (a movie about the duel between hms triad and the submarine enrico toti) is very similar.
So he understood they was pinged.
The skipper passing in engine room, saw him was smiling, and asked: are you mad? But my old (18 years old, the most young of the crew) answered: no sorry captain, only is ironic that today it s my birthday and the enemy is bombing us.
Btw i guess there was diverse types of sonars. Some like if you throw sand on the hull, or an hammer noise, others like what we see in game. But someone sad me,(source: navyman) that when they launch 1 only ping, the sound was "piing" like we know, when they was contibuosly pinging, it seems that sand was throw against the hull. All could be guys.