Its not an A330, but on an 320 test flight at the over speed prior to spoiler deployment test I noticed a "sonic wave" unless anyone has a better explanation midspan on the wing (OB of the pylon). It was a blurry line running chordwise distorting your view looking through it. It moved inboard and outboard by a few feet as the wing loading changed. On a 727 I saw a similar thing at overspeed test but it was a v shape originating at the leading edge on the very wing tip as it was vibrating madly. Mach .917 if I remember correctly. Im not an aerodynamic person, so if someone knows exactly what it is, please let me know.