AirMax sole "sound" (courtballistec) ?


for many years been using adidas shoes, but now bought nike courtballistec for a change. didn't ware nike for years, so it was bit odd to me that airmax sole makes some kind of "whoosh" sound when walking, is that normal and supposed to happened on every steep or is it something wrong with this pair of shoes and I need to go and replace them ?
it is older courtballistec 4.1 model.


Had a pair of 4.3's that did this. However, the outside of mine were bulging out because of the expanding air pocket.