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Electronic circuit designer

Discussion in 'Electronic Design' started by [email protected], Jun 20, 2007.

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  1. Guest

    I am a retired teachers looking at Voice Stress Analysis as a hbby. I
    need a competent circuit designer, professional or amatuer to design
    and build a fairly simple test board for me. Naturally, I will be
    prepared to pay any reasonable price for this work. In the first
    instance, please contact me with a price quote to produce a working
    prototype board as follows.

    The board would have a European female telephone input socket. The
    telephone input signal would be divided into two streams.

    1. One stream would be passed through to a short lead terminating in a
    male European telephone plug which could be connected to a standard
    telephone, so completing a normal telephone line.

    2. The second stream would be directed through a lowpass filter with a
    fairly sharp cut off frequency of 12 Hz. The dominant frequency
    passing though the filter would be displayed on an LED array or bar
    which would approximately show the dominant frequency in the 0 to 12
    Hz range. The device should be powered by a 9V battery and appropriate
    terminals for such a battery should be included.

    I am advised that this is not a highly complex circuit for any
    competent engineer and would appreciate anyone with the appropriate
    skills, advising me of their charge for this service and also letting
    me know somethings of their credentials, experience etc.

    Eddie Carron
  2. The circuit is simple; the rechnique is not and is widely laughed at.
    Are you hoping to make it a legitimate science?
  3. bru

    bru Guest

    I can't believe this VSA technique would even work well over a
    telephone line; if there is any true science to it wouldn't a high
    quality audio feed of the human voice allow a better analysis?
  4. AndyS

    AndyS Guest

    Andy comments:

    It looks to me like you want a spectrum analyzer with a
    frequency range of 0 to 12 hertz, that will give an
    instantaneous readout for voice inputs....
    (else how would one identify a "dominate frequency" in
    the presence of many other occurring simultaneously ?? )

    Well, if you want to "see" 0.5 hertz, you have to have a
    signal there for at least 2 seconds, probly more for any
    real accuracy......

    I would suggest an A/D converter to feed into a computer
    file, and then process the info digitally. The LPF could also
    be done digitally, and the spectrum analysis would be done
    by an FFT......

    I doubt that an analog circuit, which would have very little
    flexibility as far as experimenting with frequencies, cutoffs,
    analysis, etc, would end up giving you what you want...

    Your specifications, that is "zero" hertz, need to be
    re-thought, however.

    I'm not volunteering to do the job. But while the requirements
    seem very simple to you, once you get into the analysis of
    the problem, things may get a lot more complicated......

    Just a suggestion from an old , retired, design engineer
    who did a lot of stuff like that in the past....

    Andy W4OAH in Eureka, Texas
  5. I hope you are aware that phone lines do _not_ transmit frequencies lower then
    say 300 Hz.
    The 0-12Hz modulation is a FM modulation of spectral components _in_ the voice band.
    I suggest you lookup the theory, you missed something here.
    For the others: the technique of for example generating 'emotion' is well
    I have somewhere a module for my speech synthesiser......

    Of course the speech is in the _audible_ band say 300 Hz - up.

    Yes (for the others) it is very possible to generate a stressed sound, and in the
    same way to detect it.
    But I am no expert on this, so I cannot make this.
    I would personally start by having a look at the source code of the encoder module I have.
    Then reverse process.
    9V battery makes no sense to me either in these days.
    OP forget it or get deeper into the theory.
  6. I'm willing to bet $10 that what you really need is an
    envelope amplitude monitor at 12 Hz and below. In other
    words, you need the amplitude of all the voice frequencies
    (or some band of audible frequencies), averaged over about a
    100th of a second, and that amplitude signal measured for
    its 12 Hz and below content. Phone signals do not generally
    do not contain energy below 12 Hz, nor do most audio signals.
  7. HI,
    As others, I think you missed something : there isn't any signal in the DC
    to 12Hz band on a phone line. May I suggest a first zero cost step : why not
    connecting a PC sound card input to your phone line, may be just with a
    microphone, and analyzing the sound with a standard PC-based spectrum
    analyzer software ? Of even with more complex algorithms developped in
    Mathlab, Scilab of similar ? Once you will be 100% sure of what you want to
    extract from the audio then the hardware design will be easy.
  8. Jasen

    Jasen Guest

    No, right across, but particularly in the bottom part of that spectrum is
    the hook signalling, and pulse dialing, and In the upper parts there's
    probably noise from the start/stop of the ring signal.
    A microphone won't couple 12Hz and below to a soundcard well.

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