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Researchers Track Cell Phones Indoors By Listening In

timothy posted about 3 years ago | from the audio-daily-double dept.

Cellphones 35

starzia writes "Researchers at Northwestern University and the University of Michigan have developed a technique which aims to extend the reach of mobile phone location tracking. Their free iPhone app, Batphone, extracts a location 'fingerprint' from a short recording of ambient sound. This software-only approach allows the device to determine its location with high accuracy using its built-in microphone. Unlike prior indoor tracking techniques, Batphone does not rely on the presence of Wi-Fi access points to serve as landmarks, although these can be used to assist the system when available. They also posted a web game which allows you to test your own ability to recognize rooms by listening. Technical details are in a paper which was presented at the MobiSys conference on Thursday. This is from the same people who brought you laptop sonar."

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First! (0, Troll)

dopaz (148229) | about 3 years ago | (#36640868)

I track first posts by listening in to Slashdot.

Re:First! (0)

Anonymous Coward | about 3 years ago | (#36641020)

So, basically, there's no video games or fun. But there's still good old fakepassword3!

Sorry for coming to the garbage of this place and realizing it.


Anonymous Coward | about 3 years ago | (#36640894)

the man listening in !! Skype and Microsoft are conspirators in this, have no doubt !!


Anonymous Coward | about 3 years ago | (#36641332)

He's always trying to bring a brother down.

Neat trick, but... (1)

taiwanjohn (103839) | about 3 years ago | (#36640912)

I don't see the utility. "Gee, I can't tell if I'm in my kitchen or my living room. If only there was an app for this!"

Re:Neat trick, but... (1)

Anonymous Coward | about 3 years ago | (#36640946)

How about "Gee, I can't tell where my teenage daughter and her boyfriend are. Kitchen or Bedroom?

Get the point now? :o)

Re:Neat trick, but... (0)

Anonymous Coward | about 3 years ago | (#36641276)

No, because odds are if she is ON THE PHONE she most likely isn't bumping nasties with her boyfriend. You do realize that in order to detect sound it needs to have the microphone active and actually SEND that sound somewhere right? So, still no point to it.

Re:Neat trick, but... (2)

FiloEleven (602040) | about 3 years ago | (#36641382)

A recent court ruling in a case against the Genovese crime family revealed that the FBI has the ability from a remote location to activate a cell phone and turn its microphone into a listening device that transmits to an FBI listening post, a method known as a "roving bug." Experts say the only way to defeat it is to remove the cell phone battery.

So, no, there is no point to it from the perspective of a concerned parent. A concerned big brother, on the other hand...

Re:Neat trick, but... (1)

loufoque (1400831) | about 3 years ago | (#36641360)

How is stalking underage girls any better than stalking people in general?

Re:Neat trick, but... (1)

RockDoctor (15477) | about 3 years ago | (#36645946)

The word used was "teenage", not "underage".

You're revealing more about your interests than you maybe want to admit.

Re:Neat trick, but... (0)

Anonymous Coward | about 3 years ago | (#36646260)

If the daughter is teenage but not underage, then you DEFINITELY have no business spying on her, as she's not your legal charge any longer.

Re:Neat trick, but... (0)

Anonymous Coward | about 3 years ago | (#36661776)

How is stalking underage girls any better than stalking people in general?

When the underage girls are alone, you can rape all their virgin holes.

Re:Neat trick, but... (2)

TheRaven64 (641858) | about 3 years ago | (#36641426)

She's in the bedroom, her phone is in the kitchen. Unless the phone has a vibrate mode, in which case she and the phone are in the bedroom, and the boyfriend is in the kitchen...

Re:Neat trick, but... (2)

errandum (2014454) | about 3 years ago | (#36640948)

Or maybe "gee, I'm a boss that wants to know where their employees are, lets use something like this" :)

On a more serious note, this will require training and labeling of the system, wifi/rfid based models just work everywhere (with varying degrees of success)

Re:Neat trick, but... (1)

morgan_greywolf (835522) | about 3 years ago | (#36640992)

On a more serious note, this will require training and labeling of the system

Which, of course, means that the tinfoil hat wearers can stop thinking that this will be useful as some sort of government tracking tool.

Re:Neat trick, but... (0)

Anonymous Coward | about 3 years ago | (#36641048)

Yes, but the government has built a replica of my home somewhere and is training its system there as we write! Fortunately, I have made many changes to my property without resource consent to avoid this, unfortunately, they've probably used sonar techniques to track these changes, so I have placed devices around sending out sonar signals to phase their mapping systems.

Re:Neat trick, but... (1)

bill_mcgonigle (4333) | about 3 years ago | (#36642662)

Which, of course, means that the tinfoil hat wearers can stop thinking that this will be useful as some sort of government tracking tool.

I don't think tinfoil hats are going to be very useful here. Now, a shag carpet hat or a loaded rubber hat might change the resonant frequency of the room enough to be useful.

Re:Neat trick, but... (1)

taiwanjohn (103839) | about 3 years ago | (#36641234)

Maybe I missed something in TFA, but I don't remember it mentioning any ability to track someone else's phone, it just tells me the current location of my phone. Even if it does have that capability, it would be simple enough to spoof... just leave the phone in the kitchen (or at your workstation, etc.) while you scamper off to do something naughty.

It might be more useful if it had a shared, central database of sound profiles, which was coupled with a blueprint/map of each building. That might help if you were lost inside the Pentagon or some similar labyrinth. But most such places tend to have maps on their walls anyway.

Re:Neat trick, but... (1)

errandum (2014454) | about 3 years ago | (#36642950)

Well, with all the homework done, it could easily be adapted to spy on your employees, especially if they are using a company phone.

You could leave your company phone somewhere, true, but if someone happens to call you... :)

The shared database is a bit more tricky. I'd imagine that using the phone in a purse or in your pant's pocket would give out different signals, so each case would have to be trained individually. Only after a few months of training with enough people recording "soundprints" would you be able to use it in that way... But why would those people be using it in the first place is a mystery to me.

Re:Neat trick, but... (1)

garcia (6573) | about 3 years ago | (#36641168)

I'm in my kitchen with my phone, I'd like it to tell the server to turn the lights on and then off when I leave.

Re:Neat trick, but... (1)

gl4ss (559668) | about 3 years ago | (#36641776)

buy a motion sensor. this technique wouldn't work from your pocket anyways and do you keep your phone in your pocket at home? but what's more important is that listening to the microphone with sw keeps the cpu on and stressed.

Re:Neat trick, but... (2)

ddusza (775603) | about 3 years ago | (#36641794)

I'm in the bathroom...wait for the sound of the flush before turning off the lights this time!

Re:Neat trick, but... (1)

taiwanjohn (103839) | about 3 years ago | (#36642400)

Ok, that at least sounds like a useful application. Not sure if "sound profiling" would be my first choice for implementing it, but at least it's useful.

Re:Neat trick, but... (0)

Anonymous Coward | about 3 years ago | (#36643252)

the technology could work with anti-theft ip tracking to help provide more immediately actionable evidence. for example, if you have a picture of the guy from when he turned on your computer, you know he's at the local community college because of the wireless networks, and you know he's in the student commons because of the audio analysis, it would be pretty easy to catch him.

Countermeasure (1)

El Torico (732160) | about 3 years ago | (#36640926)

So, if I play a recording of white noise or different ambient noises, how well will this work?
Even better, a recording of a muezzin's call to prayer.

Re:Countermeasure (0)

Anonymous Coward | about 3 years ago | (#36642490)

That would likely make it easier... Listen to the samples. In nearly identical rooms, you can still hear acoustic differences. But you'll only be able to hear them if there is a sound in the room to sample those acoustics.

Where did the name come from? (2)

blindseer (891256) | about 3 years ago | (#36641320)

Is the name in reference to a bat's echolocation ability or is it a reference to the "Dark Knight" movie where such a software system was used by Batman to find the bad guys?

Only the Shadow knows.

Morgan Freeman Not Happy (2)

Kamiza Ikioi (893310) | about 3 years ago | (#36642232)

Technically, the Dark Knight software was reference to a bat's echolocation ability, so... ;) Either way, it's pretty cool... until the government gets a warrentless wiretap and uses it to watch us in our homes. If that ever happens, I can guarantee that Morgan Freeman will be pissed... again...

So according to this system.... (1)

fotbr (855184) | about 3 years ago | (#36641624)

and depending on what I was doing at the time, I would apparently have one or more of the following in my house

a) a concert hall capable of holding an entire orchestra
b) a datacenter with a crazy amount of fan noise (phone tends to get left on my desk, right next to the computer)
c) a sawmill (I'm told I snore, loudly)

I guess I don't see this being particularly useful.

Re:So according to this system.... (1)

Tynin (634655) | about 3 years ago | (#36641856)

Some schools and businesses are pretty large. I know the first few times I was walking around the old IBM building in Boca Raton ( [] ), it could have been useful. Some of the hallways are so long that if you step side to side and keep staring down the hall, the hall seems to bend like a snakes tail.

Impulse Response (1)

Edward Kmett (123105) | about 3 years ago | (#36642008)

They could probably do even better by getting the phone to emit a loud clapping sound, approximating a dirac delta so they could measure the impulse response of the room. The fourier transform of that should have some nice distinctive shapes. On the other hand, that wouldn't be nearly as unobtrusive, and most smart phones have crappy speakers, so you wouldn't get much response.

They're not alone in this effort (3, Informative)

r_jensen11 (598210) | about 3 years ago | (#36642028)

Nokia has been working on this since at least 2009, just search for their Kamppi trial [] . I know that it's fashionable to knock Nokia on many things, but they do (or is it did?) work on some very fore-front things.

Somebody else created a similar application for his Nokia phones: []

Re:They're not alone in this effort (0)

Anonymous Coward | about 3 years ago | (#36649494)

Which is what makes Microsoft and Nokia similar - both have good research but not so good development of such. The same could have been said of AT&T back when Bell Labs existed. It's a company size problem I think.

This is not new.. (0)

Anonymous Coward | about 3 years ago | (#36642082) the summary implies.

Ambience fingerprinting for indoors mobile localization has been at MobiCom since at least 2009.

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