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Education Security Software Technology

Voice Authentication for Classrooms? 28

Posted by Cliff from the my-voice-is-my-passport-verify-me dept.
USSJoin asks: "I am teaching a summer camp for gifted/talented children this summer, and one of my courses is an introduction to forensic science. One idea I had was to demonstrate voice printing and voice authentication. Using the magic Google, I was able to find software to get a visual representation of a voice print, but I didn't find anything that would allow me to demonstrate voice authentication. Ideally, I would like to be able to have students record their voices onto a cassette player, then speak into the computer, then try to fake out the computer using the tape recording. Does Slashdot have any ideas on how to demo this to brilliant young kids?"
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Voice Authentication for Classrooms? More

Voice Authentication for Classrooms?

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  • Easy (Score:1, Funny)

    by Anonymous Coward
    Does Slashdot have any ideas on how to demo this to brilliant young kids?

    Use it to protect the computer containing their final exam. They'll understand the technology backwards and forwards and have it broken by lunchtime.

  • Mac OS 9 login (Score:4, Informative)

    by parmadil ( 811515 ) <parmadil AT gmail DOT com> on Saturday July 02, 2005 @04:38PM (#12970278)
    This is probably not suitable for your purposes, but it may be interesting anyway: on Mac OS 9, it was possible to use a voiceprint to login. You'd repeat the same phrase four times, and then at login you would be asked to repeat it. The computer did show your voiceprint as you spoke.

    I remember it being fairly good for a while, but having to re-record my passphrase as my pronunciation changed over a couple months or so. Nonetheless, it was popular with myself and my family simple because it was so freakin' cool to login via your voice.

  • An idea... but you'll need a midget (Score:1, Funny)

    by Anonymous Coward
    Put a midget in a box, and call it an advanced computer that responds with voice. If they question this, ask them if they've seen Knight Rider and KITT. Have the students play their voice recordings to the "midgetputer." He'll hear the tape recording clicks and tell them they're not authorized.
  • Supposedly they use voice authentication to secure "the button" on our Nukular arsenal.
  • I found this with google, a linux pam module to login with a spoken password. May even be doable from a livecd. http://cscience.org/~lucasvr/projects/voiceauth.ph p [cscience.org]
    • "a linux pam module to login with a spoken password. May even be doable from a livecd."

      We'll just have to wait for Blu-Ray so we can just fit the voice-print of every person on the planet on the companion CD. Great idea though. Imagine a beowulf cluster of those..

      Sigh..
  • Well I can tell you now, it was Volidin. Ask Lev Rubin to match the voice prints. If they say it will take a month, give them a week. He'll need Gleb Nerzhin's help, but swiftly, because he's being transferred to one of the camps.
  • ...I have no clue about a subject I'm "teaching". What ever should I do?

    Maybe you shouldn't teach what you don't know? How about that?

  • There, they will be able to play will all kinds of state-of-the-science gadgets and devices that can teach them things like this.

    I'm sorry, but I think it's a little bit out of the "Summer camp" league.

    But please do post your findings, there have to be some "beginner" resources out there for people interested in this tech.

  • This may be a tad off, but one way of doing it would be to record their voiceprint in Audacity, then on the tape recorder, record from the tape recorder to audacity, and use diff on the output files to compare...
    though any kind of static or background noise will automatically show. The idea still holds though, you're looking for a significant noise signature between the voice and the tape player. Now supposing your tape recorders are really good, the computer might get confused.
    Oh, and make sure you've got
    • Think about this for a second. If the recording is different by one sample inserted (a .125 ms delay will do this at 8kHz sample rate), then this whole plan blows up. Humans aren't that accurate. You need some method for coping with the fact that when you speak a sentence twice there are bound to be temporal differences. For this, one ususally used dynamic time warping (DTM) or some such thing.

      Displaying it on an o-scope is slightly better, but for one it will fall victim to the same short-coming desc
      • well on an o-scope you can scale and move graphs around, so it is, in fact, very feasible. I've done it before. But I agree that diff wasn't the best idea. But hey, I dunno what other tools there are to make the difference between two wav files.
        • If you're just going to zoom in on voice, you might as well just record the voice and look at a plot of it. That would be far more repeatable. However, I don't think a human will be able to look at a time-domain representation and match it to the speaker. Looking at a spectrogram (ie a decimated short-time fourier transform plotter as an image map) would be better, but still isn't quite there. You can see formants and such, but each speaker will essentially look the same still.

          Some more info on dynami [shef.ac.uk]

    • Diff? (Score:2)

      by booch ( 4157 )
      Diff? Audio recordings are binary data. Diff only works on line-oriented textual data. Also, it's only useful with text documents that are mostly identical. Two recordings of nearly identical sounds will actually end up with VERY different data. Granted, plotting the data will look very similar, but all of the raw sample numbers will be slightly different between the 2 recordings.

      To do what you suggest, you'd need to graph the 2 recordings and then use some sort of visual comparison program to determine "h
    • Jesus H Jeremiah Christ. That is such a dumb idea it is difficult to even begin to contemplate it.

      Thats the problem with all the Linux freak fanatics. Every problem is simple to solve on a white box with the command line and the stuff you get from the gnu textutils. It must be so because its free, right??!

  • watch out for the quackery here (Score:5, Informative)

    by belmolis ( 702863 ) <billposer.alum@mit@edu> on Saturday July 02, 2005 @08:30PM (#12971246) Homepage

    I think that you need to be very careful what you tell those kids. Most of what you see on TV about voice identification is nonsense. The images that they call "voiceprints" are spectrograms: that is, they're 3D plots of the spectrum over time, with frequency on the y axis, time on the x axis, and energy represented by darkness. Phoneticians like myself use them all the time.

    In one sense every utterance, and therefore every spectrogram, is unique. The central problem in acoustic phonetics is the enormous variation in the physical signal for what in linguistic terms is the "same" utterance. The details of the signal depend on the speaker, the speaker's mood and state of health, the weather, rate of speech, choice of register (formal, casual, etc.), as well as on what other sounds the speaker is producing in the vicinity. There is a lot of contextual influence. If you compare, for example, the vowel /u/ in "tune" with that in "moose", you'll find a large difference. This one is so large you can see it just looking at the spectrogram.

    Once spectrograms became available, in the late 1940s (using a machine called the sonagraph with analog filters), people started looking for the acoustic correlates of linguistic features. They thought that it would be simple. What they discovered was the tremendous amount of variation and the great difficulty of finding acoustic correlates of linguistic features that are invariant under changes in phonetic context and the various other factors I mentioned.

    One result of this is that almost all of the research has been on abstracting away sources of variation such as speaker identity. As a result, not very much is known about the properties of the voice that are unique to individual speakers. In fact, we do not know whether voices are unique. It's clear, of course, that to some extent we can distinguish people by their voices, but we don't know that voices are truly unique, or how close they are to it.

    The upshot of this is that there is no scientific basis for determining whether two recordings, or two "voiceprints", are of the same speaker. (If they're different enough we may be able to say that they are NOT from the same speaker.) Anybody who claims to be able to look at a couple of spectrograms and testify with confidence that the same person produced both utterances is a quack. I know people who've spent substantial time debunking this stuff in court. You won't find it supported by published research.

    So, why can you login to your computer by voice? Systems like that rely on statistical "ignorance modelling". We don't know very much about what the relevant acoustic properties are, but we can make statistical models that are good enough at distinguishing one speaker from another for some applications. Even the better speaker identification systems don't work too well if they can't make a comparison between two instances of the same utterance, and as another poster mentioned from his own experience, changes in his own voice over a few months would throw off his voice login system.

    The other relevant factor here is that for some purposes its okay to have systems that make a lot of mistakes as long as they are in the right direction. If you want to limit access to a lab, let's say, it will very likely be okay to have a system that produces a lot of false negatives, that is, that incorrectly denies that the person trying to enter is authorized to. So long as you have a very low rate of false positives, the system may be acceptable.

    So, the real situation is that for some applications statistical voice recognition works well enough, but that such systems do not work well enough to be acceptable for such purposes as identifying a unique individual as a criminal. Speaker identification by visual comparison of spectrograms is junk science.

    As for software for looking at speech, there are a number of free (as in beer and as in speech) programs available. This page [upenn.edu] has some links that you might find useful.

  • You can buy fingerprint readers pretty easily and they usually come with some sort of authentication software. Buy an purely optical one (I think that Digital Persona makes one) and then try to fool it with gummi fingers.
  • For a graduate class at Goergia Tech. Voice identification/verification is not a travial problem. I don't ever recall hearing our professor talk about "voice prints."

    Most modern voice identification systems use linear predictive coded (LPC) ceptra and either hidden Markov models (HMM) to evaluate how close a a given speaker is to a known user.

    Having said that, I don't think it makes a very cool demo as the result is simply a number. In the case of speaker verification this number represents the proba

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