Abstract: A multi-pass evaporator (10) of a heat exchanger for a motor vehicle air-conditioning system includes a plurality of heat exchanger tubes (12a-t) coupled to first and second header tubes (30,32) disposed side by side. The first header tube contains an inlet tube (48) extending from an inlet end (38) of the first header tube (30) to a position intermediate the length of the first header tube (30). The ratio of the axial cross-sectional area of the interior of the inlet tube (48) to the axial cross-sectional area of the space between the first header tube (30) and the inlet tube (48) is in the range of 1:4.0 to 1:7.0. The axial cross-sectional area of the interior of the inlet tube (48) is equal to or greater than 35 mm.sup.2. This ratio of areas and size of inlet tube has been found to reduce considerably noise produced during use of the evaporator.