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Message no. 1
From: shadowrn@*********.com (Bryan Pow)
Subject: Ultrasound vision questions
Date: Tue Apr 9 10:55:00 2002
This is one for you scientists out there.
one of the players in my group is complaining because he says he should be
able to see through walls and water with his Ultrasound vision. He says that
since sound can travel through walls, and since ultrasound can be used to se
babies in the womb, then he should be able to do the same.
Is he right?
I don't want my players looking through walls but I want a better reason
than just, cos the book says so.
can you guys help?

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Message no. 2
From: shadowrn@*********.com (Marc Renouf)
Subject: Ultrasound vision questions
Date: Tue Apr 9 11:25:01 2002
On Wed, 10 Apr 2002, Bryan Pow wrote:

> one of the players in my group is complaining because he says he should be
> able to see through walls and water with his Ultrasound vision. He says that
> since sound can travel through walls, and since ultrasound can be used to se
> babies in the womb, then he should be able to do the same.
> Is he right?

Absolutely not. His assertion comes from a lack of understanding
of how ultrasound imaging actually works.
First of, ultrasound works because sound is reflected off things.
This reflection is basically caused by a difference in density between two
media (say air and a wall). Yes, part of the sound will travel through
the wall, and (after another reflection as the density changes yet again)
through the air on the other side.
If the changes in density are slight, the amount of energy
reflected is small in comparison to how much continues propagating. This
is what makes medical ultrasound work: the density difference between
the gelatin, the skin, the muscles, the amniotic fluid, and a fetus is
perceptible, allowing each of these layers to show up, but close enough
that you don't get a really hard reflection off anything.
But the stronger the difference in density, the sharper the
reflection (i.e. the less energy passes through). That's why they smear
that gel on you before they do the ultrasound - if they didn't, the pinger
would be working in air, and the transition from air to water (i.e. your
flesh) would be so great that they couldn't get any penetration.
This is exactly what's going to happen with a wall. 99% of the
energy is going to be reflected with each wall-to-air or air-to-wall
transition. So to see on object on the other side of the wall, the energy
has to make it all the way through the wall, reflect off the object, then
make it all the way *back* through the wall. And if the wall is full of
insulation, that number drops even farther. So in ideal conditions,
you're looking as something like 0.01*0.01*0.99*0.01*0.01 = 0.000000001,
or roughly 1 ten millionth of 1 percent. If you have an imaging system
that is capable of discerning a 1 ten millionth of 1 percent in dynamic
range, you're a rich man.
Further, the higher the frequency, generally the poorer it will
penetrate solid media (i.e. the more will be reflected). This is why you
can hear the bass on your neighbor's stereo through the wall, but not the
treble. Ultrasound is *very high* frequency sound. It will make a really
crisp image, but it won't penetrate for crap.
So no, you can't look through walls.
Water, on the other hand, is a different matter. If you're
actually *in* the water, then you'll be able to "see." The only problem
is that most living creatures are made mostly of water, so as far as
density transitions go, they'll look *really* strange. What your imaging
system is most likely to see is sharp transitions such as tissue to bone,
or the edges of gas-filled tissues like the lungs, stomach, or digestive
tract. Also keep in mind that high-frequency waves don't propagate as far
in water as low-frequency waves, so you won't be able to "see" as far.
But if you're *out* of the water, your ultrasound vision will
bounce off the air-water interface as though it were a solid wall. You
won't be able to see *into* the water for the same reasons you can't see
through walls.

Does this make sense? I can explain it in more technical detail
if you're curious, but the basic idea is that your player is blowing
smoke.

Marc Renouf (ShadowRN GridSec - "Bad Cop" Division)

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Message no. 3
From: shadowrn@*********.com (Anders Swenson)
Subject: Ultrasound vision questions
Date: Tue Apr 9 12:00:02 2002
On Wed, 10 Apr 2002 02:53:43 +1200
"Bryan Pow" <bryan_pow@*******.com> wrote:
> This is one for you scientists out there.
> one of the players in my group is complaining because he says he
> should be able to see through walls and water with his Ultrasound
> vision. He says that since sound can travel through walls, and since
> ultrasound can be used to se babies in the womb, then he should be
> able to do the same.
> Is he right?
> I don't want my players looking through walls but I want a better
> reason than just, cos the book says so.
> can you guys help?
>
Has your friend actually seen how much trouble it is to see a baby
using Ultrasound? You have to put the sensor right on the mother and
move it around to get different angles. It's not this little scanny
thing that sits on a desk.

You physics guys could figure out how mych flux you'd need to penetrate
solid objects, the weenie ultrasound goggles in the rulebook are good
for seeing through smoke, not for xray vision, if you get my drift.

You could invent an industrial ultrasound capable of limited xray
vision; it would be briefcase sized with a hand held sensor and a
screen.

And now, for something completely different: My pet peeve that
infravision goggles let you see warm bodies through doors, ets. HELP!

--Anders
Message no. 4
From: shadowrn@*********.com (Derek Hyde)
Subject: Ultrasound vision questions
Date: Tue Apr 9 12:10:01 2002
> And now, for something completely different: My pet peeve that
> infravision goggles let you see warm bodies through doors, ets. HELP!
>
> --Anders

Umm...being military (soon to be ex-military) and having used thermal
sights I can promise you that it's bulldrek, no way in hell, not gonna
happen unless the guy's naked and pressed against the door for a while
because the theory that the person's body heat will increase the temp of
the door and thereby allow you to see him don't work, if you stop to
think, the average room is kept just short or 70*F for comfort's sake,
the human body is (on average) 98.6*F, take into account clothing and
armor, and a distance of more than about a foot from the door there's no
way that the body's going to radiate enough heat that fast that it'll
change the temp of the room or door, lets assume he steps into a
janitor's closet where there's no ventilation to begin with, it's hot
and stuffy already so he gets the hell out of there but you saw him go
it, the door says the room's warmer than the rest of the rooms, he must
be in there huh? Go in and find the explosives he planted there so when
you were dumb enough to try and find him with thermals you didn't see
cause he's been carrying it and it was in the warm room...get the drift?
You can let your players think it works all you want but know yourself
that it doesn't, leading them on with it can be a great thing,
especially if they're trying to track someone down.

Derek
Message no. 5
From: shadowrn@*********.com (Lone Eagle)
Subject: Ultrasound vision questions
Date: Tue Apr 9 12:30:00 2002
>From: "Bryan Pow" <bryan_pow@*******.com>
>This is one for you scientists out there.
>one of the players in my group is complaining because he says he should be
>able to see through walls and water with his Ultrasound vision. He says
>that
>since sound can travel through walls, and since ultrasound can be used to
>se
>babies in the womb, then he should be able to do the same.
>Is he right?
>I don't want my players looking through walls but I want a better reason
>than just, cos the book says so.

The first thing I'd say don't worry, ultrasound used for feotal scans, and
for non-destructive testing in the engineering industry is a very different
animal to that used by bats (for example) for echo location. My memory is a
little hazy on the subject but I think it's simply the frequency that's
important and the frequency used by bats (and presumably Shadowrun vision
systems) will not noticably penetrate solid objects (otherwise the bat's
signal would simply pass through the object and we'd keep finding stunned
bats at the foot of every wall.) The frequencies used in industry are much
higher IIRC and don't travel well through gasses, which means that if your
player wants to by industrial ultrasonic equipment that's fine... but it
will need to be placed against the object he wants to check (which in the
case of a cybereye is going to be fairly uncomfortable) and the ultrasound
waves will go straight through the solid concrete (for example), his cunning
plan however does have one major flaw, while the concrete won't impede the
ultrasound at all it will bounce of everything that isn't concrete, air
bubbles in the concrete, reinforcement rods, water pockets etc but it won't
bounce off anything on the other side of the wall (unless its steel sheet or
something similar. so while he will be able to spot every weakness in the
wall he won't be able to see through it as such. Also, think of how many
flaws there are in a brick; looking through a brick, even to try to see the
piece of steel on the other side is going to be like looking through a
shattered windscreen, there will be so many flaws between you and what you
want to see that you aren't going to be able make anything out.

To put it in very simple terms ultrasonic vision relies on the untrasound
you send out bouncing off something and returning to your reciever, if the
ultrasound won't bounce of something (your wall for example) then it isn't
going to bounce off something which is less reflective on the other side of
that wall, like a human body or basically anything non-metallic. use density
as a rough guide, if the object on the other side of the wall is less dense
than the wall then it isn't going to spot it. if he wants to use his
ultrasound vision to see in the dark then it can't see through anything much
more dense than air otherwise there's no point in having it because you'll
just keep walking into things, anything much more dense than air. Not good
for a stealthy run if your "eyes in the night" keeps walking into partition
walling made of polystyrene because he can't see it!

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Message no. 6
From: shadowrn@*********.com (Bryan Pow)
Subject: Ultrasound vision questions
Date: Tue Apr 9 21:35:01 2002
It makes perfect sense, thanks. Technical detail would actually be
gratefully appreciated, you see we are part of the University roleplaying
society, and he's doing a PhD in chaemistry, while I'm doing an MSc in
Biochemistry. What this boils down to is alot of people who think they know
everything but are scientifically minded enough to accept something as long
as its proven in detail.

> Does this make sense? I can explain it in more technical detail
>if you're curious, but the basic idea is that your player is blowing
>smoke.


--
When Angels cry "Whence comes your fear?"

I shall reply "I find it here"


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Message no. 7
From: shadowrn@*********.com (Allen Versfeld)
Subject: Ultrasound vision questions
Date: Wed Apr 10 02:10:01 2002
Derek Hyde wrote:
>>And now, for something completely different: My pet peeve that
>> infravision goggles let you see warm bodies through doors, ets. HELP!
>>
>>--Anders
>
>
> Umm...being military (soon to be ex-military) and having used thermal
> sights I can promise you that it's bulldrek, no way in hell, not gonna
> happen unless the guy's naked and pressed against the door for a while
> because the theory that the person's body heat will increase the temp of
> the door and thereby allow you to see him don't work, if you stop to
> think, the average room is kept just short or 70*F for comfort's sake,
> the human body is (on average) 98.6*F, take into account clothing and
> armor, and a distance of more than about a foot from the door there's no
> way that the body's going to radiate enough heat that fast that it'll
> change the temp of the room or door, lets assume he steps into a
> janitor's closet where there's no ventilation to begin with, it's hot
> and stuffy already so he gets the hell out of there but you saw him go
> it, the door says the room's warmer than the rest of the rooms, he must
> be in there huh? Go in and find the explosives he planted there so when
> you were dumb enough to try and find him with thermals you didn't see
> cause he's been carrying it and it was in the warm room...get the drift?
> You can let your players think it works all you want but know yourself
> that it doesn't, leading them on with it can be a great thing,
> especially if they're trying to track someone down.
>
> Derek
>

*GASP*

DAMN if those aren't the three longest sentences I ever read ;)

But yes, absolutely correct on all counts



--
Allen Versfeld
Wandata
Message no. 8
From: shadowrn@*********.com (Downtym)
Subject: Ultrasound vision questions
Date: Wed Apr 10 07:05:01 2002
> <snip a very good explanation on how ultrasound works>

Sweet. I'm gonna cut and paste that into my "Newbie Guide" (tm) so
that I stop having to explain to people that ultrasound doesn't work
that way.

Downtym |
Email: gte138j@*****.gatech.edu | Post no bills
Message no. 9
From: shadowrn@*********.com (Derek Hyde)
Subject: Ultrasound vision questions
Date: Wed Apr 10 12:00:02 2002
> *GASP*
>
> DAMN if those aren't the three longest sentences I ever read ;)
>
> But yes, absolutely correct on all counts

Yeah I know, I'm talented. The problem is that when I'm typing these
things I don't really use any punctuation and separation for grammar
however if I'm writing papers they're smooth as silk...go figure...LOL

Oh well 'least I got the point across and correct huh?

Derek
(Bad writer online, great writer in class)

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