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Actuator for an active noise control system

  • US 7,206,425 B2
  • Filed: 01/21/2004
  • Issued: 04/17/2007
  • Est. Priority Date: 01/23/2003
  • Status: Active Grant
First Claim
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1. A completely inside the ear canal (“

  • CIC”

    ) speaker comprising;

    a housing adapted for insertion into an ear canal, wherein the housing has an open front portion and a closed rear portion;

    a diaphragm of diameter “

    D”

    , wherein the diaphragm is connected to housing by a suspension, wherein the diaphragm and the closed rear portion define a rear cavity volume, wherein when the housing is inserted into the ear canal, the diaphragm and an ear drum define a front cavity volume, and wherein the front cavity volume and the rear cavity volume are approximately equal;

    a magnet assembly of length “

    M”

    measured along the dimension orthogonal to the diaphragm, the magnet assembly defining a cylindrical magnetic gap; and

    a voice coil having a first portion rigidly attached to the diaphragm and a second portion placed in the cylindrical magnetic gap, the voice coil having a length “

    L”

    measured along the dimension orthogonal to the diaphragm surface;

    wherein M>

    L and the ratio defined by D/M is less than one.

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