Left mouth radical, a pictograph of an open mouth, the indexing element. Marks 噪 as a noise word: clamour, racket, the chatter of many voices or the chirp of insects (蝉噪 cicadas droning). Same family as 喊 shout, 叫 call, 哄 uproar.
Right 喿 supplies the sound directly. Beautiful semantic flavour: 喿 itself is three mouths piled on a tree (three 口 over 木), a picture of birds flocking and chattering at once. The mouth radical on the left amplifies the already-noisy graph. Family: 操, 燥, 躁.