Vehicle accessory microphone having mechanism for reducing line-induced noise

• US 20040202336A1
• Filed: 04/27/2004
• Published: 10/14/2004
• Est. Priority Date: 02/14/2001
• Status: Active Grant

• Current Assignee: Alan R. Watson, Michael A. Bryson, William R. Spence
• Original Assignee: Alan R. Watson, Michael A. Bryson, William R. Spence
• Inventors: Watson, Alan R., Bryson, Michael A., Spence, William R.
• Granted Patent: US 7,616,768 B2
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: B60R 1/12 Mirror assemblies combined with other articles, e.g. clocks
• CPC Class Codes: B60R 11/0247 for microphones or earphones
• CPC Class Codes: B60R 11/0252 for personal computers, e.g. laptops, notebooks
• CPC Class Codes: B60R 2001/1284 with communication systems other than radio-receivers, e.g. keyless entry systems, navigation systems; with anti-collision systems
• CPC Class Codes: B60R 2011/0033 Rear-view mirrors
• CPC Class Codes: H04R 1/083 Special constructions of mouthpieces
• CPC Class Codes: H04R 1/38 in which sound waves act upon both sides of a diaphragm and incorporating acoustic phase-shifting means, e.g. pressure-gradient microphone
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 2410/07 Mechanical or electrical reduction of wind noise generated by wind passing a microphone
• CPC Class Codes: H04R 2499/13 Acoustic transducers and sound field adaptation in vehicles
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

A microphone assembly includes one or more transducers positioned in one or more housings. A processing circuit is coupled to the transducer for outputting an electrical signal such that the microphone in combination with the processing circuit very effectively cancels noise. The microphone assembly can be employed in a vehicle accessory.

Claims

1. A vehicle accessory comprising:

a housing for attaching to a vehicle;

a microphone assembly carried by said 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 remote processing circuit located remote from said vehicle accessory, said microphone interface circuit comprising;

a first electrical signal path extending between said transducer and the remote processing circuit,

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

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

2. The vehicle accessory of claim 1, wherein the audio signal generated by said microphone assembly is a high-gain audio signal.

3. The vehicle accessory of claim 1, wherein said microphone assembly further comprises:

a microphone housing having a plurality of ports with windscreens provided across said ports;

a first transducer positioned in said microphone housing and generating a first audio signal; and

a second transducer positioned in said microphone housing and generating a second audio signal, the front of said second transducer facing a different direction from the front of said first transducer,

wherein said ports, windscreens and 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.

4. The vehicle accessory of claim 3, wherein said microphone housing is a separate housing from said accessory housing and is secured to an exterior of said accessory housing.

5. The vehicle accessory of claim 1 and further comprising a high frequency boost circuit coupled to said transducer for receiving the audio signal and for boosting the frequency response at high frequencies to compensate for the effect of the vehicle on the frequency response of the microphone assembly.

6. The vehicle accessory of claim 1, wherein the remote processing circuit is a digital processing circuit.

7. The vehicle accessory of claim 1, wherein said housing is a mirror housing.

8. A rearview assembly for a vehicle, comprising:

a housing for attaching to the vehicle;

a rearview element disposed in said housing for providing a view to the rear of the vehicle;

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

a microphone interface circuit electrically coupled between said transducer and a remote processing circuit located remote from said vehicle accessory, said microphone interface circuit comprising;

a first electrical signal path extending between said transducer and the remote processing circuit,

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

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

9. The rearview assembly of claim 8, wherein said rearview element is a mirror element.

10. The rearview assembly of claim 9, wherein said mirror element is an electrochromic mirror element.

11. A method for reducing line-induced noise in a first electrical signal path extending between a microphone transducer and a remote processing circuit, which is located remote from the microphone transducer, the method comprising:

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

providing a second electrical signal path extending between the impedance matching circuit and the remote processing circuit adjacent the first electrical signal path, the second electrical signal path providing the remote processing circuit with a reference of the line-induced noise present on the first signal path; and

subtracting a signal received at the remove processing circuit from the second electrical signal path, from a signal received from the first electrical signal path to cancel the line-induced noise from the first electrical signal path.