From:	Veskrashen veskrashen@*******.com
Subject:	magical effects for sea-going runners....
Date:	Tue, 16 Mar 1999 15:39:05 -0600

Starrngr@***.com wrote:
>
> In a message dated 3/16/99 2:52:57 AM Pacific Standard Time, gurth@******.nl
> writes:
>
> > On active sonar it would have the result of causing a blind spot -- the
> > ping going into the area doesn't "bounce" back to the sonar, so as
far as
> > the device is concerned, _nothing_ is there, not even the sea bed (if
> > that's "behind" the spell, looking from the sonar).
> >
> > Passive sonar listens to the sounds emitted by the target, which in this
> > case would be none due to the Silence spell. Thus, passive sonar would not
> > see anything in the area of the Silence spell. It wouldn't apear as an
> > area of nothingness, because a passive sonar doesn't get echos from silent
> > objects anyway.
>
> The problem with that logic is that the sea is NOISY. there is always
> background noise, and not hearing anything on a certain bearing WOULD be a
> dead giveaway that someone is out there in that direction. So its of dubious
> worth against passive sonar. Would work pretty good against active, tho...

Unfortunately, this doesn't hold true. Passive sonar looks for things
which ar either a) definitely man-made, or b) LOUDER than the ambient
noise. There is no real way to detect a silent area in the water; in
addition, the natural thermoclines are not detectable without active
sonar or other specialised equipment, AFAIK. the only time where
someone who was using Silence in this way would be if he/she/it passed
between an active source and some known fixed object; eg the seafloor,
a floating arcology, or whatever. Also, this would sort of a tactic
might not work against ultrasound motion sensors: the returns would be
different (from the sound waves which propogated around the spell AOE)
than without the offending object. Then again, it might, sense SR3
allows a stealth roll if you're moving slower than a certain speed.
Hmm....

Also, keep in mind that sonar equiped vessels generally dont use it
as often as they do passive sonar. It has shorter range, and gives
away your own position. Aircraft, of course, are an exception: a
submerged target currently has no recourse against them that I know
of. Thus, they dont have to care if a target sees them. However,
active sonar is generally only used after a passive sonar has produced
a good reason to believe there's something out there. So this would
actually work quite well.

Veskrashen.