Outer gate radical — simplified 3-stroke form of
門 (Kangxi #169). The indexing radical when
门 is the outer wrapper. Originally
聞 was about hearing news through a doorway, so the gate is literal — sound passing through. Same wrapper-radical anchors
间 (interval),
问 (ask),
闪 (flash),
闷 (stuffy) — characters where something or someone is at a doorway.