Stealth spell only covers noises directly made by the subject of the spell. I'm not sure an echo of an externally generated sound would count.

Eh, I guess. Unfortunately the rules for all three of those spells are just silly; as written they actually manipulate the sound waves entering the spell's effect, which is in no way the purview of an Illusion spell. Really the Illusion variants of the Silence spell ought to focus on the hearing aspect of auditory perception, just as Invisability focuses on the sight aspect of visual perception, and there ought to be a Manipulation version that focuses on the damping of physical sound waves, as the Shadow spell does for physical light waves.

While the mana version, just plain Invisibility, mucks around with living things' perception of what they're seeing, the physical version, Improved Invisibility is described in the rules as warping light. (Which leads to a whole host of questions, but that's another thread.)

There should be a similar difference between the Hush and the Silence spells, but unfortunately, the rules as written don't seem to make the distinction. The only saving grace is the fact that mana spells can only target living things. Hush couldn't dampen soundwaves, because soundwaves aren't alive.

You could say that manipulation of soundwaves and lightwaves belongs solely in manipulation, and the Illusion category should only deal with a living entity's perception. But then technically, the illusion category just becomes a specialized subset of Mental Manipulation. Why have a category at all, at that point?

There are no Illusion 'variants' of Invisibility or Silence; both of them are Illusion spells, not Manipulation. It's a game balance and simplicity issue; whether or not Improved Invisibility or other physical Illusions manipulate matter, they're still illusions. If every spell that manipulated matter was in Manipulation, then everyone would go for extra dice to Manipulation spells, as they would include all indirect Combat spells, as well as some Health spells probably. Silence and Stealth are physical spells, but the perception of the caster is that they are illusions - the silence isn't 'real' it's produced by a magical effect. Thus Silence would show up as a circular area of no echo return under ultrasound - since time of return equals distance in ultrasound, it registers as 'no ceiling' or infinite distance - a big giveaway. A Hush spell wouldn't effect ultrasound at all, since it only affects actual hearing. A Stealth spell, in my game, 'fuzzes out' a person and makes them into a man-shaped no-sound zone - easy to see but hard to track under ultrasound. I houserule that any perception-based check against a stealthed opponent is -2 to dice pool through ultrasound, but you can justify it your own way. It could be argued since the player isn't *making* the sound, Stealth wouldn't affect echoes in any way - but pseudoscientifically I rule that Stealth generates a 'force field' which eliminates any vibration from being transmitted from the body. That would stop any echoes in my mind as well.

All that being said, this thread generally falls prey to the Interdictor fallacy. The best use of Silence isn't to keep yourself from being *seen* by the ultrasound - if you drop a Silence sphere so the ultrasound detector is inside it, the ultrasound is completely blind and useless. Certaintly in terms of avoiding detection this is a bad plan, but for combat use it means that inviso-mage can continue to run around the battlefield hittin' people over the head with impunity.

Good point. In that case, then Shadow should be an Illusion spell, as it does exactly the same thing as Silence, but for light instead of sound. My aim wasn't so much to increase the number of manipulation spells so much as have spell categories be applied to different spells consistently.

Personally I'd much rather the Stealth spell be the auditory equivalent of Invisability. That is, Stealthed subjects simply have sound waves pass through them undisturbed, much like Invisability-masked subjects have light waves pass through them undisturbed. Or, rather, that's how any person attempting to see or hear them perceives

This is false. Invisibility will defeat anything sensing the visible light spectrum (debatably including infra-red and UV. Most GMs will include thos as 'defeated'.) However, along with ultrasound, it doesn't stop radar, sonar, temperature sensors, thingies that sense change in air pressure (not so much microphones, but to sense if a door has been opened), pressure sensors and the ear, mark I (plus more, of course).

Invisibility does defeat every other form of cyber eye implant, however, and every other sensor on a vehicle with sensors of 1 or below (if memory serves).

Yes see the Neo-Anarchist's Guide to Real Life for the earings (and a fashionable illustration)

I think you're right. Also I think an invisible person would set off MAD's if they were carrying enough ferrous metal. Would they set off laser trip beams though?

So? Radio waves aren't visible light. Invisibility doesn't work against the entire EM spectrum, just IR to UV.

Not precisely true. SONAR refers to using sound underwater. Ultrasound refers to using sound above the range of human hearing. Technically different, although they work on the same concept.

There are examples of old fashioned thermometers in detection systems listed in the books. They're very, very sensitive. With IR detectors, you can watch the ambient air you leave behind rather than the heat of the person himself. Once the person has moved you're detecting the hot air in his wake, like footprints in the sand.

Or the adept power whose name escapes me at the moment.

Lasers do *NOT* work against invisibility. It's IR and considered a 'vision based system'.