[忍]

There's some confusion at my table about how ultrasound works. The argument made was because we can currently use it to see inside people, there shouldn't be issue seeing through a door. To keep the game going I decided to allow it to happen. Then wasnt the time to argue it, and it didnt break the game.

Now after the fact, I would like some help to explain was Ultrasound "sees". Could yall point out any hard evidence or example to illustrate it. The description in Sensors doesn't feel like its enough to make its point.

[Tecumseh]

Ultrasound cannot be used to see inside people, unless you've cleaved those people in half with a monofilament whip. In which case you don't need ultrasound to see inside them.

Google "Daredevil vision" or "sonar vision" to get good examples. The sequence from The Dark Knight is one that many people will be familiar with.

[Marcus]

Have you ever watched the Siege?  They have a picture of a Microwave surveillance system in it.

yes it can inside physical barriers. How? It uses RF! That not enough you say? Fine It's kinds complicated.
http://science.howstuffworks.com/ultrasound1.htm

The basic principle it you send out high frequency RF waves, it goes through whatever is it, and eventually the wave field comes back, like radar.
With the help of some fairly serious processing power and a lot waves you can generate an image from the return.
 
How good is it? Lots of unknowns, on that one, the only real answer I can posit for this, would be, its as good as the core book says it is.

[ShadowcatX]

http://www.webmd.com/a-to-z-guides/what-is-an-ultrasound

[UnLimiTeD]

Of note, the Ultrasound used during pregnancies is very short-ranged; To get good images, it needs to be placed right on the skin; For better imagery a probe can be inserted.
So you might be able to look through a door, but unless you want to find out if someone is standing on the other side doing the same you won't get much information.
The Sensors used in Shadowrun are mostly closer to a Bat's orientation system.

It also can’t penetrate materials like glass that would be transparent to optical sensors.

Technically, it might depend on the material of the door, but I believe the intention of the authors wasn't to allow you to look through walls. If you want to do that, there's a TH-Radar Sensor Implant to be had.
Maybe a trained operator could be able to use a wall as a sort of 'milky mirror' to spy into the entrance of a side-alley with Ultrasound and see if someone's hiding within the first meters or so.

[Beta]

Sound reflects from 'surfaces' (including density changes inside a body, such asthe difference between heart wall and blood).  The challenge is that if there is a very strong reflection -- such as between air and a hard, dense, door -- it will be hard to tell much detail behind it.  Imagineshining a light through a very heavily tinted window and trying to make out the details of a stained glass window behind it.

if you can place your emitter/sensor tight against a hard (and solid) surface, maybe you could pick up large objects near it on the other side?  I'm not an expert, but as a GM I might give a roll at -4.

Sound carries better in water, and bodies are similar in density to water, so what things like dolphins can see is quite different than what you'll get in air.

The other to keep in mind is that sound is slow enough that the frequency of an echo will be changed if something is moving toward or away from you, so with the right analysis it is quite good at that sort of motion detection.   I seem to recall that bats make use of that, and that is what basic ultrasound motion detectors look for.

[Spooky]

Ultrasound is sound waves being emitted from a fixed location (known to the software running the system, not necessarily a fixed point in space) and the returns from that emission (the echoes) being timed to suggest where things are in relation to the emitter. This means that the first obstruction in the path of the sound waves will be what sends an echo back to the sensor, and not anything beyond it. This is why my characters have a helmet with ultrasound sensor and hud (imagelink) in it. The ultrasound image is played on the screen of the helmet, and my characters' eyes (usually with lowlight or thermographic vision) see through that screen to the world beyond. Clear as mud?

[adzling]

no, this will not work

ultrasound for seeing babies/ inside people only works because it's tuned to send and receive ultrasonic pulses through water (the human body is mostly water).

variances in density affect what is reflected and absorbed hence allowing you to build an image

an ultrasound sensor in air works totally differently.

it cannot go through anything, instead bouncing off the first surface/s it encounters.

perhaps it could go through something with lots of airgaps, like lace, but that would degrade the signal very quickly and not work very well at the best of times.

so NO, ultrasound does not let you see THROUGH things due to PHYSICS.

Also the game has something that does this, kind of, with many limitations. It's the cyberware radar sensor.