| 摘要 |
PURPOSE:To improve a noise decrement effect ever so better, by setting the distance connected rectilinearly an interval between two points where a branch duct and a ventilating duct are connected with each other, the distance connected the interval between these two points with a center line of the branch duct and a wavelength of such a sound as being wanted to reduce its sound pressure, to specified relations. CONSTITUTION:An air conditioner bearing the above caption is provided with a ventilat ing duct 8 installing inside and outside air suction ports 3 and 4 in its one end while a blowoff port 16 leading to the inside of a car room in the other end, a blower unit 5 to send air to the blowoff port 16 from these inside and outside air suction ports 3 and 4 and a branch duct 9 connecting an interval between vertical two points of the ventilating duct 8. In this case, when length rectilinearly connecting center points 9a and 9b of each opening part in the branch duct 9 is set down to l1, and length connected from the center point 9a to the center point 9b along the center line of the branch duct 9 is set down to l2 as well as a wavelength of such a sound as being wanted to reduce its sound pressure among noises to be propagated to the ventilating duct 8 is set down to lambda, the distance l2 is set there so as to satisfy an equation of l2-l1=(lambda/2)(2n-1)X(1+ or -0.1).
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