Quote:
Originally Posted by BulSoldier
Funny i always thought that the sonar uses freqencies(spl?) that are beyond human capabilities to hear.
|
ASDIC used frequencies between 14 and 22 kilocycles at the upper end of human hearing. Each ship using ASDIC had to use a different frequency to avoid detecting each others return signals. 20 Kilocycles is considered at the very upper limit of human hearing for signals of normal intensity (human voice spoken normally), in air but the density of water changes the upper limit somewhat along with the fact that ASDIC pings had to be reasonably loud to carry up to 2km from the transmitter and get a return signal, so those ships using 22Kilocycles would have been almost impossible to hear but those below that range were certainly audible.
Most of the recordings that exist today of ASDIC are from the operator's console aboard an escort ship fo some kind. I've not found one that was recorded aboard a WWII submarine that was being pinged but it would be interesting to hear the difference.
This excellent article covers some of the issues raised here:
http://jproc.ca/sari/asd_gen.html
According to the Maritime Musem of Liverpool this is a recording of an ASDIC capable ship approaching and passing over a target:
http://www.liverpoolmuseums.org.uk/m...dio/asidic.mp3