Patent ID: 7266204

Claim:
A rearview assembly for a vehicle comprising: a housing for attaching to the vehicle, said housing defining an interior space; a device for providing a rearward view of a scene behind the vehicle; and a first speaker located in said interior space of said housing, wherein a front acoustic chamber is defined between a front of said first speaker and an interior surface of said housing, said front acoustic chamber having a volume V, at least one port having an acoustic resistance r A is provided through said housing in front of said front acoustic chamber, and wherein said front acoustic chamber and said at least one port are configured to satisfy the following equation: pc 2 ⁢ r A pc 2 + j2 ⁢ ⁢ π ⁢ ⁢ fr A ⁢ V = ∑ i = 1 n ⁢ ⁢ 12 ⁢ ⁢ μ ⁢ ⁢ ω _ i d 3 ⁢ l i + j ⁢ 12 ⁢ ⁢ p ⁢ ⁢ ω _ i ⁢ π ⁢ ⁢ f 5 ⁢ l i ⁢ d where: f=resonance frequency; n=number of ports; ω i =width of port i; l i =length of port i; d=wall thickness of the housing; p=density of air (in g/cm 3 ); μ=viscosity coefficient=1.86×10 −4 for air; and c=velocity of sound (in cm/sec).