From: Lewis Jardine (
Date: Thu 30 Jan 1997 - 20:30:38 EET

Hi All

Thomas gives us some good Sonar info (which I was pleased to see
confirm much of what I (a non-specialist) had managed to glean.)

> That also means that using sonar through mist or rain is more
> efficient than dry air.
While it might be more efficient I suspect that it would be pretty
aweful WRT image quality. Two things spring to mind immediately:

1) Each droplet would act as a divertent sonar lens, this might give
a very nice diffused "sonic rainbow effect" WOW!
2) There might be back-scattering from the droplets (although here I
am not sure about the reflective properies of the air-water interface)

> - - About Hollowness:
> The great thing about sonar is that, using it, you can "see" *inside*
> anything you're looking at. Just like the scanning done on a pregnant
> woman. A dolphin, as well as a troll, can say if someone is pregnant,
> what that person had for dinner, and so on.
Yup, us fathers (& mothers) can attest to ultrasound scans.
However the stronger reflections from the surface might well mask out
interior reflections unless you were up close and well connected...
By this I mean that ultrasound has to be connected using a similar
density medium (KY-Jelly!) to get maximum energy transfer.

> IMO, that means that a troll can say if a pregnant female is expecting
> trollkins or dark trolls.

Only if she is very friendly!

> - - About techniques:
> The usual technique for efficient hunters like sperm whales or orcas
> is the following:
> First, the hunter scans the whole area using a wide and unaccurate
> beam of sound, at low frequencies that can travel very far, that give
> him a general idea of potential preys.
> Then, he focuses a narrow beam of higher frequencies on the prey to
> receive accurate data about it.
That sounds like Dark Scan and Dark Search to me.

> - - Using sonar as a weapon:
> Orcas, sperm whales and belugas, among others, can use their sonar as
> a weapon: they send a very strong sound wave against their prey, and
> can stun or even kill it that way! (the target has to be of limited
> size, though, like a salmon for example).
> It it a lot more difficult to use sonar that way in the air, but in a

> fantasy world, it certainly has a potential MGF.

Again energy transfer could be a problem,
But watch out for sea-trolls underwater.

Well all the about is RW technical, IYG I would always recommend MGF.



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