Look into loop induction earphones, been around for years.
  Just one link:
http://www.hearing-loss-help-co.com/index.htm?371.htm&1

-carl

At 03:08 PM 4/8/2003, you wrote:
>I have an applicaton where I would like to be able to talk to somebody
>(remotely via radio). However I would like nobody around them to hear what
>is being said. Also it should not be noticable that they have any sort of
>hearing device on(e.g headphones).
>
>I thought about using bone transmission of sound. You could give them a
>little ball with a speaker inside it and when they want to hear they bite
>the ball and the sound travells through the teeth into the ears.
>
>Anybody know anything about this or have any other ideas??
>
>Cheers.

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