ASDIC Question

[Sir Big Jugs]

Hi,:)
I'm currently reading a Swedish book on U-boat warfare in WWII called "Havets Vargar" (Wolves of the Sea) by Michael Tamelander and Jonas Hård af Segerstad.
Without going into too much detail about the book itself, I found the following (very roughly translated) footnote interesting:


An ASDIC pulse can't be picked up by the human ear, but a small "click" sound might be heard inside when it hits the hull of a submerged submarine. The well known 'PING' from many U-boat films could actually only be heard by the escort's ASDIC operator.
The ASDIC receiver converted the returning ultrasound echo to a sound at ~1000Hz (where the human ear is most sensitive) in order to make it hearable to the ASDIC operator. This converted sound was the charasterictic 'PING'.
Can anyone confirm/deny this? The authors both have a reputation for being quite meticulous in their research, and having read other books by them I hold them quite high in this regard.

On the other hand, I would be surprised if this potential mistake hasn't have been caught earlier, so they're probably wrong.:hmmm:

Hope someone knows the answer!

Regards,
-SBJ

[GoldenRivet]

From what i have read, there were several types of ASDIC used.

some of which were well within the human range of hearing. others were too high pitched for human ears to hear.

whether or not you hear the distinctive "ping" like we are all too familiar with depends on which type of ASDIC is being deployed against you

[kaptkirkU4467]

Oh..you can hear it.


Hans Goebler: U-505 Submariner
"two minutes later, the radioman shouted a report up to Zschech through the conning tower hatch, informing him of what we all could hear with our bare ears: we were being scanned by Asdic. The pause between each Asdic "ping" was rapidly getting shorter. They had obviously located us and were headed right towards us. "

[Sailor Steve]

Some uboatmen have described it as sounding like a handful of gravel being thrown against the hull.

[UberTorpedo]

Yep. Pretty much like these sounds http://files.filefront.com/Authentic+Sonar+Soundszip/;12321639;/fileinfo.html

[GoldenRivet]

positively sickening sounds :nope:

[Oneshot/Onekill]

I concure with the majority here also. I would like to know what type of ASDIC the author's are refering to? The early war ASDIC from the little research i've done operated on a much lower frequency, very audible to the human ear.

[bobchase]

Sonar comes in many kinds & flavors. A wideband pulse, also known as a multi-frequency pulse, can sound like gravel being thrown against the hull. The receivers back then did use an 'audio translator' for the operators of the sonar, as well as a Echo Scope for a visual indication. Single frequency pulses may not be heard at all, depending on the transmit frequency used. On the other hand, you can definitely hear a 'ping' if it's primary frequency is down in the human range of hearing. Very, very, definitely, yes, you are going to hear it.

It was true in '42 and it was still true in the summer of '72 when we (myself & 1200 of my closest friends) were walking up & down the NV coast, shutting down CD sites, slot radars, and SAM sites as fast as we could reload. We had started going after some WBLC's (water born logistics craft) when a Ruskie sub came around and started to have a 'ping' session with us. Unfortunately we didn't have anything to ping back with and, like most bully's, it just made them bolder. We didn't sleep for days thanks to that enemy sonar because it was like Chinese water torture on steroids. You'd just get to drift off towards sleep and then !PING! And that cycle would repeat itself itself over and over, hour after hour, all day and all night. The only escape was up on deck and we could only do that if we were not on watch, engaged in a firing mission, or were far enough from land so as not to take incoming. Most sailors were trapped inside a very big bell.

However, after a few days of that s**t, a very nice 688 class boat came along our way and set things straight. I'm sure some Admiral carrier squadron commander was pissed off to loose half of his sub screen for a couple of days but we were just delighted to have them come on in towards shore and hang around.

At least we were after the 'pinging' contest was over. Our sub had pulled up right along side them and started really pinging back. Loud & fast. So the Ruskie countered with an even louder pinging. Then the 688 skipper decided enough was enough and showed them the kind of wattage that the US uses its sonar. For an hour or so there, it was like being Quasimodo in the bell tower. Then the Ruskie gave up and slinked back into the depths that they came from and silence. Wonderful, sweet, silence.

Sorry for the long sea story but the answer is yes, it can sound both ways. I've heard them both.

Bob

[Otto Heinzmeir]

Interesting real life story!:yeah:

[Sir Big Jugs]

Thanks for clearing this up! Didn't know there were many different types existing.:)
I'm not certain exactly what type of ASDIC the quote was about, but AFAIK it was mounted on the V&W class destroyer HMS Walker in March 1941 and used for the successful attack on Otto Kretschmer's boat U-99.

Bobchase, interesting story, thanks for sharing!:salute: