Why does new Ikea furniture (Kallax) make a liquid sound when moving?
Yes, it can be very true indeed that the 'wooshing sound' that you are talking about is the result of the scrap material that was left unchecked during the production of the furniture. Many a times when hollow parts/ material (like the bamboo arms for wooden chair) are used for designing the furniture, the fine particles of wood dust or scraps resulting from the use of chisel or any other tool may get accumulated into these cavities.
I have been working as a furniture repair guy at the Austin Furniture Repair where I have a lot of these cases. So, rest assured as it might not really be that big a problem. Hope it helps!