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Induction-based assistive listening system

  • US 4,908,869 A
  • Filed: 05/09/1989
  • Issued: 03/13/1990
  • Est. Priority Date: 05/09/1989
  • Status: Expired due to Fees
First Claim
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1. A system for addressing hearing-impaired persons within a targeted audience by the generation of specifically configured audio-frequency magnetic field at pickup coils worn by said hearing-impaired persons comprising:

  • (a) transducer means for converting an acoustic signal into an electrical voltage signal possessing substantially the same Fourier spectrum as said acoustic signal;

    (b) means for dividing said electrical voltage signal into a multiplicity of identical electric voltage signals;

    (c) time delay means for introducing various discrete delay times into each of said multiplicity of identical electric voltage signals so as to produce a multiplicity of delayed electrical voltage signals;

    (d) means to amplify each of said delayed electrical voltage signals;

    (e) a grid of electrical conductors embedded in a flexible mat wherein said mat comprises;

    (i) a bottom layer of flexible material;

    (ii) a top layer of flexible material;

    (iii) means for fastening said top layer over said bottom layer so as to sandwich said grid between said top layer and said bottom layer. and said grid comprises a planar arrangement of least one pair of electrically isolated conduction loops, each of said conduction loops further comprising an electrically-linked plurality of substantially uniform, substantially rectangular sub-loops, each rectangular sub-loop having a length dimension equal to approximately four times its width dimension and further where all of said sub-loops of one member of a given pair of said conduction loops are arrayed so as to have their long sides parallel to the long sides of all of said sub-loops of the other member of said pair and are further arranged so that each of said sub-loops of one member of said pair is displaced along its width dimension by a distance equal to one-half the magnitude of said width dimension from the nearest sub-loop belonging to the other member of said pair of electrical conductors; and

    (e) means for connecting each of said time-delayed electrical voltage signals to a single one of said conduction loops so as to generate a single current in said single one of said conduction loops such that the current variation produces the same waveform which was associated with said acoustic waveform and where current amplitude produces an audio-frequency magnetic field amplitude of approximately 100 ma/meter at an elevation of 0.5 meters above said mat.

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