whooping sound on 2006 Honda Odyssey

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
After driving for a while on a trip, there is a whooping sound that seems to come from the A/C in the back.It could be in the front, not sure. You can hear it inside the car. It does not happen unless you have been on the road for a while with the air on. The dealership is clueless. Any help out there? It sounds like whoop, whoop and then stops. I was told it may be the A/C fan berring wearing out.
(2) Answers
find another shop that can diag it for you. sounds right about the fan

My guess is it is NOT the bearings. My guess is it is an improperly presurized A/C system.
See this link:

Especially, note the logic of the statement made by dwest1023 in his "11-11-2007, 11:22 AM " post.

In any case, you are not alone, and A/C systems the world over are "Whooping it up".