Vehicle accessory microphone having mechanism for reducing line-induced noise

  • US 7,616,768 B2
  • Filed: 04/27/2004
  • Issued: 11/10/2009
  • Est. Priority Date: 02/14/2001
  • Status: Active Grant
First Claim
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1. A vehicle accessory comprising:

  • an accessory housing for attaching to a vehicle;

    a microphone assembly carried by said accessory housing and comprising at least one transducer, the microphone assembly generating an audio signal;

    a microphone interface circuit electrically coupled between said transducer and a digital signal processor (DSP) located remote from said vehicle accessory, said microphone interface circuit comprising;

    a first electrical signal path extending between said transducer and the DSP;

    an impedance matching circuit for providing an electrical connection to ground having an impedance matching that of said transducer;

    a second electrical signal path extending between said impedance matching circuit and the DSP adjacent said first electrical signal path, the second electrical signal path providing the DSP with a reference of the line-induced electrical noise present on said first signal path such that the DSP may cancel the electrical line-induced noise from the first electrical signal path by subtracting the electrical noise signal received from the second electrical signal path from the signal received from the first electrical signal path; and

    wherein said at least one transducer includes a first transducer positioned in a microphone housing for generating a first audio signal and a second transducer positioned in said microphone housing for generating a second audio signal, the front of said first transducer facing a different direction from the front of said second transducer, wherein said transducers are configured such that said microphone assembly exhibits a first polar pattern with null aimed at a driver of the vehicle, and a second polar pattern with a null aimed at a front passenger area of the vehicle.

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