The only direct translation I found for Wummern is boom. A booming sound.

PAM-FLOW provides users with best-of-breed technology for identifying and quantifying flow-induced noise sources. Carmakers like General Motors optimize noise performance due to sunroof buffeting and car appendages, while suppliers use PAM-FLOW to predict flow-induced noise in rotating machinery.

http://www.hoise.com/primeur/01/articles/monthly/AE-PR-04-01...

Passengers of road vehicles with open sunroofs often experience considerable discomfort associated with strong periodic, self-sustained flow oscillations. This phenomenon, referred to as sunroof “buffeting”, causes intense pressure fluctuations within the passenger compartment at the frequencies between 10 to 50 Hz. This quasi-tonal oscillation is due to the vorticity generated by the flow over the opening (sunroof).

http://widget.ecn.purdue.edu/~me615/Projects/projects.htm

We know it is important to you, but having the largest opening is not always an advantage, as it can cause wind buffeting. This is when air comes in through the sunroof and creates a build-up of air pressure inside the cabin. Most of Webasto's electric HOLLANDIA sunroofs can be programmed to stop in a position other than full open, to reduce wind buffeting. This is another unique feature.

http://www.autosun.com.au/showcase.asp

Wummern is a hammering sound or a deep drumming sound.

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Note added at 23 mins (2004-05-25 16:04:49 GMT)
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Cilian\'s \"rumbling\" sounds good, too (No pun intended.)
So: anti-hammering position or anti-rumbling position.