Originally posted by reallynobody
Originally posted by Tom Bedlam
[3) "Electric currents" aren't sent to submarines. That would be "radio" or EM fields. Another indication the author is clueless.

Infrasonic sound is used to communicate with submarines, it is the only thing that get's trough when a sub is deep underwater. Radio and "EM
fields" are useless.
Unless they let antenna buoy's float to the surface to pick up radio. That can get you caught ofcourse, and you have to slow down or stop.
It may even be ultrasonic sound that can be hold responsible for the deaths of many wales. People usually blame sonar, however wales can hear
infrasonic sound and use it for communication. How would you like it if someone blew a foghorn next to your ears? Not to mention that it could rupture
membranes in their bodies directly.

You're quite incorrect here. Infrasonic sound is not used for or by submarines.
You're apparently also mangling low frequency sonar (LFAS) and higher frequency sonars in a submarines acoustic suite. A towed LFAS such as SURTASS
is not infrasonic either. Infrasonic would have to be less than 20 Hz. SURTASS is 50-250Hz, a deep bass at the bottom end but definitely not
infrasonic. SURTASS in specific, and LFAS in general, are used to search for submarines at great distances using sound channels, which is where you
may have gotten confused.
Sub sonars are typically around 1KHz for tactical sonars, and >10KHz for object search sonars such as mine hunting sonar or ice depth sonar. Mine
hunting sonar may actually BE ultrasonic, that would be a sonar operating over 20KHz. The higher the frequency, the more resolution a sonar has, but
the shorter the distance it can operate over.
So, infrasonic is definitely NOT ultrasonic, in fact they are opposites. Sound is also not radio (all radio is an EM field), a trivial sounding fact
that seems to baffle a certain contingent, just in case you were wondering. A 1KHz radio signal is not audible, for example.
Submarines mount communication buoys as you have possibly seen on movies (remember a lot of the movies you see, "Crimson Tide" being a prime
example, are not at all accurate). However, communication buoys are not used until the submarine knows a communication is pending.
The US (and Russia) use ELF to address deeply submerged submarines. The maximum modulation rate at the frequencies we use is quite slow, so the
communications sent over ELF are short predetermined code sequences. As the sub comes shallow, it can switch to VLF and receive communications at a
slightly higher rate, or the code sequence may instruct them to deploy a buoy or come shallow enough to raise an EM mast. Think "periscope" with
antennas on it.
You're trying to teach your granny to suck eggs here. I've got a bachelors in physics, a masters in EE comm theory and working on my PhD in the
computational physics of underwater acoustics. Not to mention nearly 20 years working as a defense contractor. Don't make me pull out Maxwell on ya.
There are at least three methods for receiving ELF at depth that are in use even as we speak.
[edit on 5-7-2006 by Tom Bedlam]