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Hearing Aids

Discussion in 'Electronic Design' started by PaPaPeng, Feb 24, 2006.

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  1. PaPaPeng

    PaPaPeng Guest

    There is a discussion in a disabilities support group about the latest
    hearing aids having an induction loop and digital circuitry. Is
    anyone familair with the technology innovations?

    Two questions.
    1. In what way will digital be better over analog? After all the
    requirement is only to amplify sound, not process it - a case of
    simplicity over complexity. Even if an analog hearing aid picks up
    everything at a noisy cocktail party for example, the human brain is
    still the best mechanism to filter out the extraneous noise.
    2. What does the induction coil do in in the hearing aid. My guess is
    that it allows an outside oscillator to induce a current in the
    hearing aid thereby eliminate the need for an internal battery. Its
    like the charger for miniature remote control cars at Radio Shack.
     
  2. colin

    colin Guest

    Im not 100% sure but I think the Induction loop is used to broadcast sound
    to hearing aid users from say a speaker using a microphone. maybe telephones
    too?

    As for digital processing I heard this is claimed to allow much larger
    volume amplification by dynamicaly altering the response to avoid feedback
    noises. Im not sure if the technology even exists to distinguish wanted
    noises from unwanted ones.

    Colin =^.^=
     
  3. Joel Kolstad

    Joel Kolstad Guest

    I know next to nothing about hearing impairments, but I'm fairly certain that
    in many cases deafness occurs only over specific frequency range(s). That is,
    the hearing loss is not just a "flat line" attenuation, but is a significant
    function of frequency. As such, it's much easier to create an "inverse" gain
    response with digital techniques that it is with analog.
    That's pretty subjective. Radio operators use electronic filters all the time
    to improve signal intelligibility, and although the "noise" coming over a
    radio has a different distribution than the noise at a cocktail party, it's
    not much of a leap to suggest that having the ability to filter a signal in
    ways other than those that your brain alone provides is useful.
    I'm not certain, but besides providing power to an implanted receiver, I would
    venture that it probably also transmits the audio itself.

    ---Joel Kolstad
     
  4. Steve

    Steve Guest

    Incorrect. The aid should amplify only those sound frequencies which
    the ear is not hearing normally. Deafness is usually not a "linear"
    problem, high frequency loss is common. Different patients may cut
    off at different frequencies. A modern hearing test involves first
    plotting the response of the ear across the whole of the normal audio
    spectrum. A modern digital aid is then programmed by computer to
    amplify frequencies where the ears respose is abnormally low. It
    therefore is customisable for the individual patient. Indeed a
    frequency plot and programming is done for each ear, left and right
    sides may vary for the same patient. If you amplify all frequencies
    equally you will just confuse the picture. My son for example has
    severe high frequency loss, but normal low frequency hearing, straight
    amplification of everything would not be a good thing in this
    situation. Older analogue aids did have a configurable frequency
    response curve, but it was not so customisable as with the digital
    aids and computer s/w.

    Harder not easier though if you are being deafened by loud and
    unneccesarily amplified low frequencies which the ear hears normally.
    Induction loops are a method of directly coupling audio to the aid,
    hence avoiding the listener having potentially confusing background
    sounds also amplified. Cinemas for example can transmit sound this
    way if so equiped. Also telephones, whatever. The aid has a "T"
    switch on it which switches over from normal microphone to loop input.

    Steve
     
  5. Joerg

    Joerg Guest

    Hello Colin,
    Sometimes both, power transfer and signal transfer.

    It does. There are filter algorithms and slopes that are next to
    impossible in the analog world. It's tough to say that as an analog guy
    but that's the way it is. Depending on the case and severity of hearing
    loss such filtering must be quite intense. Also, it is much better
    programmable for a custom solution than analog. Some applications such
    as cochlear implants would be almost impossible in an analog fashion.

    Then there are costly component tolerance issues which are eliminated in
    a digital design.

    Regards, Joerg
     
  6. Joerg

    Joerg Guest

    Hello Steve,
    Is there a standard? This would be good for places like our church. We
    have a radio wand system but have to hand out analog wands that just
    feature a simple volume control. Plus they break all the time. I've got
    one here right now where the potmeter became erratic. Again.

    Regards, Joerg
     
  7. Jim Thompson

    Jim Thompson Guest

    "Potmeter"?? What are you smoking at that church ?:)

    ...Jim Thompson
     
  8. Joerg

    Joerg Guest

    Hello Jim,
    ROFL!

    Ok, yes, we are in California but it doesn't go that far...

    It's a drag. Much of that "professional" gear is easily repairable yet
    often they won't ship you parts or require to send it in to a 'certified
    repair facility', meaning lotsa $$$. We could somehow find that potmeter
    but I bet then we'd have to do a minimum buy of a whole crate.

    Regards, Joerg
     
  9. John Fields

    John Fields Guest

     
  10. John Fields

    John Fields Guest

    ---
    In CA, I think that's called a "toke" ;)
    ---
    ---
    If you wanted to install an inductive system, I'll bet John Woodgate
    could help you out since ISTR that he has some expertise in that
    area.

    Where is he, anyway?

    Prob'ly got tired of the crap on this channel...
     
  11. Steve

    Steve Guest


    Yes there does seem to be a standard, don't know the official name for
    it. See the URL below. Places of worship are mentioned in the FAQ
    here as a suitable application for the technology. There is a
    standard symbol which can be displayed at sites where T loop is
    available, which you might recognise, see:

    http://www.hearingloop.org/fq_preferred.htm


    Steve
     
  12. Joerg

    Joerg Guest

    Hello John,


    Hmm, never heard that before. Then again, I didn't grow up in CA. And I
    didn't grow anything either :)
    IIRC he signed off a while ago because of some job, I think. But it's
    been a while.

    Regards, Joerg
     
  13. Joerg

    Joerg Guest

    Hello Steve,
    Interesting, thanks! I had asked a few of our hearing impaired and none
    had ever heard about such a system. Looks like it would be around $2k
    for our size church if we do the install as volunteers. That's more than
    the existing system but considering the convenience it would make sense.
    As long as I can find out whether the majority has T-Loop enabled
    hearing aids.

    Regards, Joerg
     
  14. dunno, miss his wit, He's one of the good guys here, along with Win
    and Jim (ooops)


    martin
     
  15. I have seen his cross-posts from sci.lang.translation recently, so it
    wasn't entirely work-related...


    Best regards,
    Spehro Pefhany
     
  16. Jim Thompson

    Jim Thompson Guest

    Well! There certainly hasn't been any requests for serious circuit
    design help here in a very long time, so I guess I'll have to just
    keep picking on leftist weenies :-(

    ...Jim Thompson
     
  17. Joel Kolstad

    Joel Kolstad Guest

    We're hoping you're going to start writing that book of yours, Jim. :)
     
  18. John Fields

    John Fields Guest

    ---
    So what am I, chopped liver?

    Hundreds (maybe thousands) of _free_ designs which work, schematics
    which are easy to read and build from and, since I don't blow my own
    horn too often, anonymity, more or less.

    Lucky me, I get to die as an unknown...
     
  19. Jim Thompson

    Jim Thompson Guest

    Keep me loaded up with "exercises" and I'll start writing. Writing,
    by itself, is terribly boring... after all it's an "I did that
    already" task.

    Reminds me, my wife is very active in charities and Girl Scouts.
    Nearly 30 years ago I had a sculpted gold pendant made for her....

    (o)
    I
    DID
    THAT
    ALREADY

    (Except that "THAT" was properly half-spaced ;-)

    ...Jim Thompson
     
  20. Steve

    Steve Guest

    Seems as if there is more awareness of T-Loop here locally in the UK.
    It's common to see the sign in banks for instance, as the teller has
    to use a microphone to talk accross the security glazing. All the aids
    son Tom has been supplied with have a T setting. Check out a major
    player like Siemens if you need more detail on them

    Steve
     
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