Hi guys, i just started playing a few weeks ago, and created a character which relies mostly on stealth skills. I was just wondering... does Ultrasound automatically detect an infiltrating character regardless of his infiltration check? I know there is a rule to bypass motion sensors (which use an ultrasound field to detect motion) by succeding an infiltration check, threshold of 3 and moving at half a meter per combat turn. Is there a similar rule for the ultrasounds character can have or do they just see you regardless? thx for the help guys!

A character with an ultrasound vision enhancement/similar modification has to make an opposed perception check against the infiltration roll. However, invisibility spells, ruthenium camouflage, light modifiers etc. will not count against the ultrasound roll.

So no. There is no automatic detection.

It operates as a normal camera under SR4 rules. I guess one would remove most visibility penalties but add penalties for interpretting the image due to the alien nature of an ultrasound image compared to normal imaging. Range would be more limited and certain environments would make them near impossible to use. I'm not actually certain how common ultrasound noise is, but since everything is GM fiat anyway you shouldn't have to worry about that.

Given that ultrasound imaging is relatively common in security applications in 2070, I'd expect most characters trained in stealth will have a practical grounding in avoiding being detected by it.

Yeah. Check the vision modifier table.

of course, if you have radar vision, then you can also ignore the things the target is behind... still not automatic, but seeing through walls helps a lot for noticing the guy under the cardboard box.

Something thats always had me thinking...what sort of sounds would one use to spoof or obscure the ability of ultrasound to "see"?

Obscure things by putting out ultrasound yourself, or by modifying the surface structure of your gear for diffuse reflection. Absorbing sound waves may or may not help depending on the distance and type of the next object behind you.

Send out regular chirps on all ultrasound bands in wide angles; they detect the distance from the source by checking the time delay on echoes, so spamming in all bands messes that up and they get static instead of a good image. I'm not sure you can absorb ultrasound, it reflects from transitions between materials with different acoustic properties.

I'm no ultrasound expert, I just got taught about it in a little detail as part of a medical physics course.

Of course in that way they would still know SOMETHING was up, but not where or who. Diffuse reflection is the most effective means.