

Communication with submarines - TriinT
http://en.wikipedia.org/wiki/Communication_with_submarines

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yan
That reminds me of a project I almost undertook a few years ago with a friend
of mine. We wanted to transmit video from a custom-built submarine using
sound.

At first, I remember seeing an image embedded in Aphex Twin's
"Windowlicker"[1] and thinking it can't be that hard to write software to
recreate it. Not knowing much at the time, I came to a friend of mine who was
all about signal processing, who whipped up a binary to do it a few days
later[2].

Skip forward a few months to when me and a friend are discussing communicating
with submarines and transmitting stuff like video data, and how impermeable
salt water is to RF. So one of us pitched the idea of using that method of
embedding images in sound via that method, and we figured if we use a high-
enough audio frequency and low-res image (say 400x400px), we can transmit a
roughly 4 fps video stream and use ~50px for control data.

Also, noise won't be an issue here, since the signal is for human consumption
and blips and distortion can be overlooked. I ended up buying a pair of really
decent transducers removed from an old nuclear submarine (!), but ended up not
being able to implement this as life got in the way.

If anyone needs a pair of decent 10W underwater transducers, let me know :P

[1] <http://en.wikipedia.org/wiki/Windowlicker> [2]
<http://134.74.16.64/wwwa/web/hardware/soundmural/>

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rbc
Voice communications via acoustic means has been around since World War 2.
Look for the UQC systems. They used single sideband modulation. VLF broadcasts
have been around for a long time as well. During the 90's, I'd walk into radio
on the USS Cavalla to go on watch and we almost always had the VLF fleet
broadcast coming in on the teletype printers.

~~~
notmyname
Technically, hasn't "voice communications via acoustic means" been around a
lot longer than that?

~~~
rbc
Well, I meant in the context of communicating with submarines, the subject of
the Wikipedia article.

------
livando
Conn, radio, request number one bra-34, request permission to transmit two
released outgoing messages via SSIXS.

