1940 air cleaner question

[Thomas Sargent]

Just received an air cleaner that is correct for my 40 ford flathead from ebay. Looks nice but looking at it carefully, I see the air enters the top thru the screen and mesh, and then goes straight down into the carb throat thru a small tube in the center. What is the purpose of the chamber that surrounds the down tube? It has no air inlet, just is common to the opening at the bottom. Can't see or understand it's purpose. Thanks