2010-2011 Audi models may exhibit a high frequency (whistling) wind noise at highway speed, caused by air flowing through the exterior rear view mirror at the seam where the turn signal lamp meets the housing. This affects 2010 A3, A4/S4A5/S5, 2011 A3, A4/S4 A4/S4, A5/S5 and A5 Cabriolet models.
The fix involves the simple addition of a sealing strip in the mirror housing. Perform the strip installation to both mirrors, even if the source of the noise is diagnosed as coming from only one mirror.
Remove the cap of the exterior mirror housing. Attach a strip of sealing foam tape in the area shown in Figure 3. The strip will be the correct length to extend from the corner of the lip to the angle in the body line. No modification of the strip should be necessary.